EVALUATING THE INFLUENCE OF HISTORICAL AND CURRENT LAND COVER ON SEDIMENT AND NUTRIENT TRANSPORT By Christopher L. May A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Geological Sciences 2011 ABSTRACT EVALUATING THE INFLUENCE OF HISTORICAL LAND COVER ON SEDIMENT AND NUTRIENT TRANSPORT By Christopher L. May Alterations to historical land cover along with the spatial variability of current land cover can directly impact groundwater flow and the water quality of streams. As human population grows, land cover will continue to be altered, enhancing its importance. This study examines how changing land cover affects recharge to groundwater and groundwater transport to streams. The impact of historical and current land cover on hydrology in the Jordan River Watershed was modeled. The geometry of the sediment deposited within the Jordan River was studied using Ground Penetrating Radar to correlate changes in sedimentation to past land cover and climate change. Ground Penetrating Radar combined with sediment cores aided in the interpretation of certain sediment packages. The last part of the study examines total dissolved Phosphorous and Nitrate groundwater inputs from land cover by modeling the transport of nutrients through the Sycamore Creek Watershed. Nutrient loading for different land covers and in-stream processing for Total Dissolved Phosphorous and Nitrate were optimized to match measured stream data. ACKOWLEDGEMENTS I would like to thank my advisor, Dr. David Hyndman, for his help and guidance through this process. I am also thankful for the insight and help that have been provided by other two committee members, Drs. Remke van Dam and Warren Wood. I am very grateful for the help and advice given by my colleague Dr. Anthony Kendall. A thanks also goes out to Dushmantha Jayawickreme, Abby Norton, Sherry Martin, and Mine Dogan for their help at various stages of this study. This work was made possible by the funding from the Friends of the Jordan River, National Science Foundation, and the Environmental Protection Agency. A thanks also goes to Dr. Jan Stevenson, Seth Hunt, and Nick Welty for their contributions to the data collection and sample analysis. I finally want to thank my wife Sara for her continued support and inspiration. iii TABLE OF CONTENTS LIST OF TABLES ................................................................................................ vi LIST OF FIGURES ............................................................................................. vii CHAPTER 1: EVALUATING THE IMPACTS OF LAND COVER CHANGES ON STREAM FLOW BEHAVIOR................................................................................ 1 INTRODUCTION............................................................................................... 2 Site Description.............................................................................................. 6 METHODS ...................................................................................................... 16 Model Inputs ................................................................................................ 16 Steady-state Model ...................................................................................... 26 Transient Field Data..................................................................................... 32 Recharge Calculations for Land Cover ........................................................ 40 Transient Model ........................................................................................... 44 RESULTS AND DISCUSSION ........................................................................ 47 Model Results .............................................................................................. 47 Implications for Sediment Transport ............................................................ 49 CONCLUSIONS .............................................................................................. 52 BIBLIOGRAPHY.............................................................................................. 55 CHAPTER 2: USING RADAR STRATIGRAPHY TO EXAMINE THE RESPONSE OF HISTORICAL SEDIMENT TRANSPORT TO LAND COVER ALTERATIONS................................................................................................... 59 INTRODUCTION............................................................................................. 60 Site Description............................................................................................ 62 METHODS ...................................................................................................... 67 Ground Penetrating Radar........................................................................... 67 GPR Data Collection.................................................................................... 69 iv GPR Processing .......................................................................................... 71 Auguring ...................................................................................................... 72 RESULTS AND DISCUSSION ........................................................................ 74 Borehole Data .............................................................................................. 74 GPR Signatures ........................................................................................... 76 GPR Interpretation ....................................................................................... 80 CONCLUSIONS .............................................................................................. 81 BIBLIOGRAPHY.............................................................................................. 83 CHAPTER 3: EVALUATING THE INFLUENCE OF LAND COVER ON NUTRIENT TRANSPORT AND IN-STREAM NUTRIENT PROCESSING ......... 85 INTRODUCTION............................................................................................. 86 Site Description............................................................................................ 89 Source and Sinks......................................................................................... 91 METHODS ...................................................................................................... 93 GIS Data ...................................................................................................... 93 Steady-state Model ...................................................................................... 99 Groundwater transport using MT3D........................................................... 102 Optimization using a simple 1-D In-stream Processing Description........... 107 RESULTS AND DISCUSSION ...................................................................... 109 Optimization Results .................................................................................. 109 Final MT3D Model Results......................................................................... 110 CONCLUSIONS ............................................................................................ 118 Acknowledgments...................................................................................... 119 BIBLIOGRAPHY............................................................................................ 121 v LIST OF TABLES Table 1.1: Values for hydraulic conductivity after optimization for geologic zones shown in Figure 8B. The starting hydraulic conductivity value for all the geologic zones for the optimization was 5 m/d ................................................................. 30 Table 1.2: Total rain and runoff data collected by Onda on hill slopes near Point Reyes, California immediately following a forest fire. This study used rainfall and runoff data to calculate runoff ratios which was the basis for the precipitationrunoff relationship. Values in red indicate the collection tank was full and did not actually record all the rain. Event 1 recorded 6.51 inches, but the actual rainfall was 7.96 inches. Event 6 recorded 1.43 inches but the total rainfall was 2.46 inches. Thus, 7.96 and 2.46 inches were used in the runoff-precipitation relationship. Modified from Onda (2008) ............................................................ 42 Table 2.1: Various materials and their relative permittivity and velocity, Modified from Baker (1991)............................................................................................... 69 Table 3.1: Simulated flow and averaged measured flow at three locations ........................................................................................................... 101 vi LIST OF FIGURES Figure 1.1: The Jordan River Watershed (JRW) is located in lower Northwest Michigan (MIGDL) ................................................................................................ 7 Figure 1.2: Hydrograph, with precipitation, of the Jordan River at the United States Geological Survey (USGS) Webster gage # 04127800. Flows and precipitation plotted from 01/01/07-09/01/08 ........................................................ 8 Figure 1.3 A map of percent slope from the digital elevation model (A) for cells in the Jordan River model area. Slopes in the Jordan River Valley (B) (shown by the blue rectangle) contain the highest relief within the drainage basin. Numbered locations refer points on the elevation profile for the Jordan River (Figure 1.4) (Source, USGS SEAMLESS) .......................................................... 10 Figure 1.4: Elevation Profile along the Jordan River (blue line), relative to a simple equilibrium profile (black line). The elevation profile was generated using the points along the river that were extracted from the DEM (Figure 1.3A). The red are locations marked on the river in Figure 1.3 ............................................ 11 Figure 1.5: Old railroad beds can be found in the Jordan River valley as linear paths of bare ground .......................................................................................... 13 Figure 1.6: Agriculture as percent land area from 1900-1950 for the three counties within the model area (See Figure 1.1 for county locations) (USDA).... 14 Figure 1.7: Land Cover Statistics (A) for the three different land cover data sets and maps for pre-developed (B) and for current, 1978 MIRIS, (C) land covers (MIGDL).............................................................................................................. 17 Figure 1.8: GIS maps for soils (A) and surface geology (B) (MIGDL)................. 20 Figure 1.9: Lake coverage of water, oil, and gas wells within the model boundary shown in black (MIGDL). The red outline is the surface watershed.... 22 Figure 1.10: Drift thickness map (A) created from the interpolated bedrock elevation (B) (MIGDL)......................................................................................... 24 Figure 1.11: Annual precipitation used to calculate recharge and runoff for the Jordan River model area, includes snowfall (NCDC and MAWN) ...................... 26 Figure 1.12: Simulated map of heads (A), along with a comparison between simulated vs. observed heads after PEST optimization (B)................................ 30 vii Figure 1.13: Shows the JRW and groundwatershed (shaded) for the Jordan River within the model area ......................................................................................... 32 Figure 1.14: Map showing gage locations within the Jordan River Watershed (highlighted in red) (A) along with their stage-discharge relationships: USGS Webster (B) Graves (C), Fisheries (D), and Deer (E) ......................................... 34 Figure 1.15: Spatial channel cross channel geometries for all the sites where flows were conducted ......................................................................................... 37 Figure 1.16: Temporal cross channel geometry at Graves (A) and Deer Creek (B) gage locations. See Figure 1.14A for gage locations ........................................ 38 Figure 1.17: Discharge at all four stream gages in response to Precipitation Events. Arrows indicate lags (MAWN, NCDC, and USGS) ............................... 39 Figure 1.18: Precipitation: Runoff relationship used to calculate infiltration and runoff. Modified from Onda (2008)..................................................................... 44 Figure 1.19: Approximate recharge for estimated for different land cover scenarios within the model area ......................................................................... 45 Figure 1.20: Simulated Flow for Current Land cover within the Jordan River model area plotted with stream flow and base flow for the USGS Webster gage (USGS) ............................................................................................................... 48 Figure 1.21: Simulated stream flow at USGS Webster for all four tested landscapes ......................................................................................................... 48 Figure 1.22: Hjulstrom’s diagram showing velocities required for the entrainment and deposition of different sediment sizes. Modified from Prothero and Schwab (2004) ................................................................................................................. 50 Figure 2.1: The Jordan River Drainage basin is in the northern portion of Michigan’s Lower Peninsula (MIGDL) ................................................................ 62 Figure 2.2: Lake Level data for the NOAA gage for Lake Michigan and Lake Huron. The dotted line shows the approximate level of Lake Charlevoix before the opening of the channel between Lake Michigan and Lake Charlevoix (NOAA). Lake levels are monthly averages........................................................ 64 Figure 2.3: Study area showing GPR lines, auger boreholes, and Vibracoring locations adjacent to the Jordan River and Lake Charlevoix. The numbered locations will be referred to in the text (MIGDL).................................................. 66 viii Figure 2.4: GPR antenna setup during data acquisition in the winter of 2008. Photo by Christopher L. May .............................................................................. 70 Figure 2.5: GPR processing algorithm. Arrows indicate the progressive processing steps applied to the GPR data ......................................................... 71 Figure 2.6: Borehole data collected in the summer of 2007. All surface sediment was a very thin (<1cm) layer of organics from current riparian vegetation and was excluded from this graph. Boreholes are highlighted in Figure 2.3 .................... 75 Figure 2.7: A) Raw 2-D GPR data profiles shown with line numbers that correspond to the GPR grid shown in Figure 2.3. Letters S, C, and M represent sand, clay, and muck respectively, found in cores that coincided with GPR lines .................................................................................................... 77 Figure 2.8: GPR profiles shown with 1 type of interpretation (light blue lines) .... 78 Figure 2.9: GPR profiles with interpretations of concave-up reflectors (red lines)............................................................................................ 79 Figure 3.1: The model area along with Sycamore Creek Watershed (SCW, highlighted in pink) is located in South Central Michigan (from MIGDL)............. 90 Figure 3.2: Map of Current Land cover for the Sycamore Creek model area (MIGDL).............................................................................................................. 92 Figure 3.3: A 9 meter resolution DEM plotted with the model area (bold outline) and the SCW (light outline) (SEAMLESS) .......................................................... 94 Figure 3.4: Surficial Quaternary Geologic Map used for geologic facies description for MODFLOW and MT3D (Farrand and Bell, 1982) ........................ 95 Figure 3.5: Wells used to construct the map of the aquifer bottom, for water level observations, and to provide septic well inputs. Wells used inside the model boundary (yellow line) were used to simulate nutrient inputs from septic systems (MIGDL).............................................................................................................. 96 Figure 3.6: Variogram model (using a Circular model, 255 m range, 164.14 nugget, 100 sill, 100 m lag size, 12 lags, and no anisotropy) (A) incorporated into the interpolation of the bedrock elevation map (B) ............................................. 98 Figure 3.7: Simulated heads plotted relative to observed heads (A) and mapped (B)..................................................................................................................... 101 Figure 3.8: A) Nitrate observations, B) TP observations (Welty, 2005) ............ 105 ix Figure 3.9: Optimization results for Simulated and Observed total and differential fluxes for Nitrate (A, B) and TDP (C, D) with in-stream processing coefficients........................................................................................................ 111 Figure 3.10: Simulations based on the final optimized nutrient concentrations from Agriculture, Pasture, Septic Tanks, and urban areas ............................... 113 Figure 3.11: Simulated and Observed TDP Flux from different land cover for Sycamore and Mud Creeks .............................................................................. 114 Figure 3.12: Simulated and Observed Nitrate Flux from different land cover for Sycamore and Mud Creeks .............................................................................. 115 Figure 3.13: Simulated and Observed TDP Concentration from different land covers for Sycamore and Mud Creeks ............................................................. 116 Figure 3.14: Simulated and Observed Nitrate Concentrations from different land cover for Sycamore and Mud Creeks ............................................................... 117 x CHAPTER 1: EVALUATING THE IMPACTS OF LAND COVER CHANGES ON STREAM FLOW BEHAVIOR 1 INTRODUCTION Land cover alterations can affect recharge (Jayawickreme and Hyndman, 2007), stream flow (Mutie et al., 2006), as well as fluvial geomorphology and stream ecology (Poff et al., 2006). It is important for management agencies to understand the effect of land cover changes on the environment as the human population grows. Alterations to the landscape such as logging, forest fires, landslides, and farming can have significant impacts on stream flow and sediment transport within a drainage basin. Significant changes in stream flow or sediment transport can adversely affect stream ecosystems and degrade the water quality, all of which can impact public water supply and recreation. Examples of land cover alterations that can lead to changes in stream flow and sediment transport include: forest fires, agriculture development, logging, and landslides. Studies have shown that logging can impact stream flow and sediment transport thus leading to degraded water quality. Logging in the drainage basins increased peak base flows, and overall sediment concentrations during high flows (Waterloo et al, 2007). Cassie et al. (2002) found no changes to annual or seasonal water yields in the middle reach or upper reaches after timber harvesting of 2.3 and 23.4 % of the middle and upper reaches of the drainage basin respectively, but peak flows increased in the upper tributary of the drainage basin. Other studies (Hibbert, 1967; Bosch and Hewlett, 1982) showed that peak flows, as well as annual and seasonal water yields only changed if greater than 2 20% of the total area was harvested. Other implications of logging include rising water tables, and higher snow accumulation rates (Dube and Plamondon, 1995; Winkler et al., 2005). Landslides substantially change stream flow and sediment transport in a drainage basin. Timber harvesting can increase the risk of landslides because the absence of canopy cover leads to increased soil moisture and decay of roots, which can lead to rapid soil saturation and the loss of soil strength (Johnson et al., 2007). Other events that can cause landslides include earthquakes (Yang et al., 2010) and heavy rain on slopes that contain only a thin layer of sediment over steeply dipping rock (Saito et al., 2009). Landslides in turn are a major source of sediment from steep valleys (Mikos et al., 2006). Kasai (2006) showed that landslides can also change the fluvial geomorphology of a river system for long periods of time by modifying the path of the river. Forest fires can change channel morphology by decreasing bank stability, physically changing the characteristics of the soils, and reducing evapotranspiration (ET) (Dickman and Leefers, 2004). Batalla (2001) showed forest fires can change stream flow behavior through large runoff events related to hydrophobic soils created during the fire. Various studies have looked at effects of forest fire on soils, runoff, erosion, and nutrient loss (Neary et al., 1999, Cerda, 1998, Pierson et al., 2008, Onda et al. 2008, Tessler et al., 2008). Because changes in stream flow due to land cover are being evaluated, the biggest effect that a post-fire land cover would induce is a change in runoff. Runoff is only considered in the post-fire land cover because this is one of the 3 few instances where runoff could occur within the JRW due to its course-textured sediments. Water repellency (WR) by soils is heavily dependent on the temperatures during a fire. Neary et al. (1999) discussed the expected temperature ranges of fires occurring within different land covers (i.e. 200-300° C for forests, 300-700° C for shrubs). The two types of wildfires that likely occurred within the JRW would be slash fires of material left behind after tree harvesting, which can have temperature ranges between 500-700 C, and forest fires in predeveloped landscape. Intense water repellency would have only occurred during forest fires in the JRW and not from the slash that tree harvesting left behind because the repellent layer tends to be destroyed at temperatures greater than 280° C (DeBano, 2000). Agricultural development has been shown to affect several aspects of the water cycle, which in turn change both stream flow and sediment transport. For example, differences in tilling can affect different runoff behaviors during precipitation events (Baker, 1983). Warnemuende, et al. (2007) showed that fields with conventional tilling have 50% of the runoff than fields with no tilling, however, they also show that sediment loss rates were greater for fields with conventional tilling than those with no tilling. Wiley et al. (2010) found that if current urban sprawl patterns, in the Muskegon Watershed (located in Michigan), continued at their present rate that agriculture would be reduced along with some loss of forested land cover. This would have significant effects of the hydrologic cycle in such basins. Drainage basins with intense agriculture in Michigan 4 (greater than 60%) had less late-summer stream base flow than drainage basins with less agriculture (Jayawickreme and Hyndman, 2007). Models have been used to evaluate linkages between land use alterations and changes in percolation and recharge (Selle et al., 2008; Thomas and Tellam, 2006), and to help solve water sustainability issues (Schuol et al., 2007). This study examines the effects of land cover alterations on recharge and stream flow within a modeling framework, and evaluates two major alterations to land cover within the Jordan River Watershed (JRW), agriculture and forest fires. Forest fire and agriculture represent the extreme range of expected changes that have affected stream flow in the JRW in the past 150 years. Logging would only remove the native canopy and not have the WR of post-forest fire landscapes that would create large fluxes of runoff to streams (Batalla, 2001). A logged landscape would also not have the high evapotranspiration of agriculture landscapes (Kendall, 2009; Hyndman et al., 2007). Thus agriculture and post forest fire landscapes would show more extreme effects on hydrology than logging. Landslides were not included because no data could be found with records of timing and location of historical landslides that could add sediment to the Jordan River. The conceptual model for a forest fire that occurred in the JRW could have created large amounts of runoff that would have also changed recharge and stream flow. A 100% agricultural land cover in the model area is used to test how much recharge and stream flow could have changed with the absence of any native canopy. The native canopy was assumed to have been completely destroyed in the conversion from forest to agricultural fields in this 5 scenario. Along with the two altered land cover scenarios, pre-developed land cover (primarily forest) and current land cover (urban, agriculture, and forest) are also simulated for comparison. Percent land cover for pre-developed and current land covers were calculated using available GIS datasets. PrecipitationRecharge ratios derived from the Integrated Landscape Hydrology Model (ILHM) (Kendall, 2009; Hyndman et al., 2007) were used to estimate how much precipitation becomes recharge for each land cover type. The recharge, derived from the precipitation-recharge ratios in ILHM, were then input into MODFLOW (McDonald and Harbaugh, 1988) to simulate stream flow for each land cover scenario discussed above. The flow simulations results are then discussed in the context of how such modeled changes in stream flow would potentially affect sediment transport and stream channel morphology. Site Description The Jordan River Watershed (JRW) (Figure 1.1) is an excellent natural laboratory to observe the impacts of land cover change on hydrology. The JRW has a documented history of logging, forest fires, farming, and possible landslides since its early settlement in 1840. Residents of the basin recall a gravel bottom river with diverse fish habitat. However, sand transported in the river channel has reportedly filled in much of the gravel bottom, negatively impacting fish habitat. Fish, such as Brook Trout rely on gravel for spawning, thus this ecological attribute is highly valued (Klingeman et al., 1998). 6 Figure 1.1: The Jordan River Watershed (JRW) is located in lower Northwest Michigan (MIGDL). For interpretation of the references to color in this and all other figures, the reader is referred to the electronic version of this thesis. The Jordan River drainage basin consists of outwash deposits and course-textured end moraines. As a result, much of the precipitation within the drainage basin infiltrates into the sediment and the vast majority of stream is derived from groundwater rather than overland flow (Hay and Meriwether, 2004). The peak flows in the River are caused by direct precipitation on the water or near stream runoff after snow melt events (Figure 1.2). The Jordan is unlike many rivers as it carries a stable flow, which varies little throughout the year. However, the Jordan River can flood during spring thaw as ice blocks temporally dam the river (Fuller, 2002; Sui et al., 2005). The Jordan River also has a very 7 large discharge to drainage basin area ratio, which indicates groundwater capture from adjacent surface water drainage basins. 450 0 400 0.5 Discharge (cfs) 300 1 250 200 1.5 150 100 Precipitation (inches) 350 2 50 0 1/1/07 2.5 4/1/07 6/30/07 9/28/07 12/27/07 3/26/08 6/24/08 Date Figure 1.2: Hydrograph, with precipitation, of the Jordan River at the United States Geological Survey (USGS) Webster gage # 04127800. Flows and precipitation plotted from 01/01/07-09/01/08. The JRW has two distinct segments, the upper and lower Jordan River, distinguished by changes in stream gradient and sinuosity. The upper part of the Jordan River contains very steep terrain with a stream gradient of 0.76% or 7.61 m/km resulting in flow velocities of up to 1.5 m/s. The lower part of the Jordan River has significantly lower gradients of approximately 0.080% or 0.80 m/km and slower average measured velocities of 0.8 to 1 m/sec. The upper part of the Jordan River has much higher sinuosity than the lower part of the Jordan River (Figure 1.3), which is related to disequilibrium in the river elevation profile (Figure 8 1.3). Most river elevation profiles for systems that are in equilibrium can be characterized with a smooth exponential curve. In contrast, the elevation profile for the Jordan River has a sharp drop in gradient between 1 and 11 km from its headwaters that could be caused by either a landslide or by the bedrock topography. A landslide could have been initiated after removal of vegetation during logging or after a forest fire along the steep slopes adjacent to the Jordan River. Bedrock that is resistant to erosion can prevent the Jordan River from rapidly down cutting, which could cause the river to migrate laterally with significant lateral erosion of the sides of the valley. As will be discussed later, the bedrock topography varies greatly across the model area and appears to be influence the path of the Jordan River, especially in the upper part of the Jordan River and in its largest tributary, Deer Creek. 9 Figure 1.3 A map of percent slope from the digital elevation model (A) for cells in the Jordan River model area. Slopes in the Jordan River Valley (B) (shown by the blue rectangle) contain the highest relief within the drainage basin. Numbered locations refer points on the elevation profile for the Jordan River (Figure 1.4) (Source, USGS SEAMLESS). 10 400 3 2 300 250 1 200 40000 30000 20000 10000 0 River Elevation (m) 350 150 Distance (m) Figure 1.4: Elevation Profile along the Jordan River (blue line), relative to a simple equilibrium profile (black line). The elevation profile was generated using the points along the river that were extracted from the DEM (Figure 1.3A). The red are locations marked on the river in Figure 1.3. Although Deer Creek is the largest tributary to the Jordan River, approximately half of the area of the JRW, it has relatively low flow for its surface watershed. At the confluence of Deer Creek and the Jordan River, the flow of the Jordan River averages approximately 180 cubic feet per second (cfs) where Deer Creek has only 20 CFS. The base level of the Jordan River is the level of Lake Charlevoix where it deposits its sediment. Before settlement of the Jordan River Valley in 1840, the area was dominated by coniferous forests (e.g. white cedar, white pine, hemlock) along the river and deciduous forest in the upper parts of the valley (Hay and Meriwether, 2004). The Great Chicago Fire of 1871 created a demand for timber which greatly 11 increased timber harvesting across the northern peninsula of Michigan (Dickmann and Leefers, 2004). Up to eight logging companies operated out of East Jordan including: Vince’s Sawmill, B&C Saw Mill, South Arm Lumber Company, and Nelson Reddington & Co. Lumber Mill, after logging started in the lower part of the drainage basin in 1879 (Hay and Meriweather, 2004). During the logging period, the lower part of the Jordan River was used to carry logs into the southern arm of Lake Charlevoix (Hay and Meriwether, 2004). By the 1900’s, logging moved into the upper part of the drainage basin where conifers were cut first in the lowlands and deciduous trees were cut last in the highlands. The upper Jordan River did not have sufficient stream flow to transport these logs, thus railroads and teams of horses were used to transport logs to Lake Charlevoix (Hay and Meriwether, 2004). Evidence of the old logging railroads can still be seen today (Figure 1.5). Logging continued until 1930 and took several years to transport to Lake Charlevoix. Logs that sunk in the old harbor can still be observed today in the vicinity where the Jordan River flows into Lake Charlevoix. 12 Figure 1.5: Old railroad beds can be found in the Jordan River valley as linear paths of bare ground. The landscape of the JRW was also likely altered by forest fires (Dickmann and Leefers, 2004). It is not known for certain that forest fires occurred within the JRW but such events would likely have had serious implications on the hydrology. The surface and subsurface hydrology would be changed after a forest fire as transpiration ceases and soils become water repellent, causing an increase of surface runoff and erosion and decreasing infiltration (Batalla, 2001). Widespread forest fires occurred in Michigan during the 1870’s, some of which swept across the shores of Lake Michigan to the shores of Lake Huron. Significant forest fires were the Bad Axe Fire of 1881, the Metz Fire of 1908, and the Au Sable-Oscoda Fires of 1911 (Dickmann and Leefers, 2004). One major 13 fire that likely occurred within the JRW is the 1911 Au Sable-Oscoda fire that was observed in Antrim (Dickmann and Leefers, 2004). Hay and Meriwether (2004) also reported that several fires occurred within Antrim County in the 1930’s after logging ended, but the JRW was not mentioned. From 1900 to 1920, data from the USDA agriculture census showed that farming increased in the model area from 0% to more than 50% of the drainage basin area as forest landscapes were converted to open landscapes during timber harvesting (Figure 1.6). From 1920-1930 the agricultural area decreased by 5% within the model area. An estimated 650 of the 1,750 original farms within the JRW stopped operating between 1920-1930 due to nutrient poor sandy soils (Hay and Meriwether, 2004). 60 Percent of Land Area 50 40 30 20 10 0 1900 1910 1920 1930 1940 1950 Year Antrim Charlevoix Otsego Figure 1.6: Agriculture as percent land area from 1900-1950 for the three counties within the model area (See Figure 1.1 for county locations) (USDA). 14 Since 1930, the upper part of the JRW has returned to being mostly forest. In 1972 the Jordan River was declared the first Natural River in Michigan, which resulted in a large amount of the land in the drainage basin being converted to state forest (Hay and Meriwether, 2004). Currently coniferous forests are only 15% and deciduous forests are the dominant land cover type at 55% (Figure 1.7). The other major land cover types are open grass lands (15 %) and agriculture (16%). 15 METHODS Model Inputs MODFLOW within the Ground Water Modeling System (GMS) was used to construct steady-state and transient flow models of the Jordan River model area, which was expanded from the drainage basin to include part of both arms of Lake Charlevoix to the North, the Boyne River to the east, and the Cedar River to the west. It was also determined that the Jordan River groundwatershed extends well beyond its surface drainage divide to the south. A digital potentiometric surface map was created by interpolated water levels in wells and lakes that were connected to the groundwater using Wellogic data, from the Michigan Geographic Data Library (MIGDL), which was then used to show direction of groundwater flow and no-flow divides. The groundwater flow divide to the south was represented as a no-flow boundary in the model. Several GIS (Geographic Information System) data sets are used as inputs for a groundwater model. Two land-cover maps, from the MIGDL, were used to represent conditions before settlement and for the current time period. The 1800-predevelopment map illustrates the native land covers, primarily forest and wetlands, before large scale human disturbances (Figure 1.7). The predevelopment map was generated from historical surveys conducted by the MFI (Michigan Features Inventory, 2008). The current land cover used the 1978 MIRIS (Midwave Infrared Imaging Spectrograph) coverage, which was created from aerial photographs. More recent land cover data is available with the 1992 16 IFMAP (The Integrated Forest Monitoring, Assessment, and Prescription) coverage; however this dataset was not classified in the same manner as the earlier data, and thus was not used. 100 90 80 Landcover (%) 70 60 50 40 30 20 10 0 Ag. CON. DECID. OPEN URBAN WETLAND Anderson Land Cover Type 1800 Land Cover 1976 MIRIS 1992 IFMAP A Figure 1.7: Land Cover Statistics (A) for the three different land cover data sets and maps for pre-developed (B) and for current, 1978 MIRIS, (C) land covers (MIGDL). 17 Agriculture Coniferous Trees Deciduous Trees B Open Open Water Rangeland Urban Wetlands C Figure 1.7 continued 18 Another major input for the groundwater model is the lithology of soils and shallow sediments through which the water flows. Soil lithologies were used in the calculation of precipitation-recharge ratios, which will be discussed in more detail later, to help estimate the recharge into the glacial aquifer. The main sediment types within the model area are sand, sandy loam, and loamy sand (Figure 1.8). The map was generated from a digitized State soil maps by STATSGO which was then merged with information on soil parent material (Farrand and Bell, 1982). Most of the geologic units are glacial outwash and course-textured tills (Figure 1.8). The highly permeable soils result in the stable flow of the Jordan River because a large proportion of the precipitation in the system becomes recharge, which eventually reaches the stream as groundwater discharge. 19 Figure 1.8: GIS maps for soils (A) and surface geology (B) (MIGDL). The Digital Elevation Model (DEM) is used to create a series of data sets (Figure 1.4A), and as a result, is one of the most important data sets. The 1/3 arc second DEM, with a 10x10 meter cell size, was created from the National Elevation Data set, derived from aerial photos and USGS quadrangle maps. The 20 data, which was processed by the USGS for missing data and artifacts in the dataset, was extracted from the National Map SEAMLESS Server (non-boundary constrained data sets). The sources/sinks and boundary conditions for the MODFLOW model are the Jordan River along with any of its tributaries and lakes (i.e. Lake Charlevoix and Deer Lake). The lakes and rivers within the model were downloaded from MIGDL (Figure 1.9). Most of the small lakes that were connected to the river were used as draining features instead of constant head boundaries. Lake Charlevoix was the only lake to be specified as a constant head boundary, at 177 m above MSL, in the model due to its size relative to the other lakes and its connection with Lake Michigan. A Digital Raster Graphic of the United States Geological Survey (USGS) 7.5 Quadrangle Map (DRG), dating 1997 (MIGDL, 2007), was used to assign the elevation of Lake Charlevoix. 21 Figure 1.9: Lake coverage of water, oil, and gas wells within the model boundary shown in black (MIGDL). The red outline is the surface watershed. Water wells were used to calculate starting heads along and observed water levels were used for model optimization. Oil and gas wells were used to calculate the bottom aquifer geometry. The water, oil, and gas well logs, which were digitized by the Michigan Department of Environmental Quality (Figure 1.9), provided measured water levels for a dataset of observed heads to be compared against simulated heads from the steady-state MODFLOW model (Harbaugh et al., 2000). Wells were filtered spatially by displaying the wells by county and any well located outside of its county were deleted from the data set. Then the DEM was used to filter out well logs that had differences between the DEM elevation and the recorded elevation for ground surface greater than plus or minus one 22 meter. Well logs were also filtered by the hydrologic unit that the wells were completed in. For example, if a well was completed in bedrock, then head observations were not used for model comparison. A total of 190 wells were used for water level residual analysis in the simulations. The bottom aquifer geometry is an important boundary for the groundwater model. A bedrock elevation map was constructed within ArcGIS using the depth to bedrock values within oil and gas well logs, which penetrated bedrock. The oil and gas wells were filtered based the ground surface elevation being within 1 meter of the DEM elevation. The bedrock elevations were estimated by subtracting the depth of bedrock from the recorded surface elevation for each well site. Outliers, where bedrock elevations were inconsistent with those from surrounding oil and gas wells, were removed before interpolation. 3,315 oil and gas wells were used in the creation of the bedrock elevation map using ordinary kriging within the ArcGIS Geostatistical Analyst. Other maps such as the USGS map created by Soller (1992) of the Glaciated United States do not have the resolution as the maps shown in Figure 1.10 or detail on the sub- 23 kilometer scale. Bedrock elevation (m) 176 30 A Glacial Drift Thickness (m) 360 50 B Figure 1.10: Drift thickness map (A) created from the interpolated bedrock elevation (B) (MIGDL). 24 In order to evaluate stream flow response to land cover alterations, precipitation was used as an input to estimate recharge for the groundwater model. Hourly precipitation data was downloaded from National Climate Data Center for the Bellaire NOAA (National Ocean Atmospheric Administration) gage from January 1997 through June 2008. Due to the unavailability of hourly precipitation from June through December 2008, data for this period was from the Michigan Automated Weather Network (MAWN) at the Eastport gage, approximately 15 km west of the model area, was used to fill in the missing data gap. MAWN was not solely used because the gages use non-heated buckets which lead to poor estimates of monthly precipitation during the winter. Standard climate was used in this study, which assumes that the climate observed today was relatively the same from the late 1800’s through the early 1900’s. Unfortunately standard climate does not exist from the 1800’s to the early 1900’s, thus the ten years of precipitation data from NCDC and MAWN was used as a standard climate for the flow models with different land cover scenarios (Figure 1.11). 25 100 90 Precipatation (cm) 80 70 60 50 40 30 20 10 0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year Figure 1.11: Annual precipitation used to calculate recharge and runoff for the Jordan River model area, includes snowfall (NCDC and MAWN). Steady-state Model Simulations of transient groundwater flow require starting heads and boundary conditions. A 3-D steady-state groundwater model was constructed to estimate starting heads for the transient groundwater model. A transient groundwater model is able to simulate the groundwater fluxes when initial conditions and transient data (i.e. daily precipitation) is available. A 3-D groundwater flow model grid was constructed within GMS. The model grid contained 724 columns by 729 rows, with approximately 50x50 meter cells. The surface elevations from the 10x10 meter DEM were interpolated to the center of the 50x50 m flow model cells using linear interpolation. Cells inside the 26 boundary were assigned boundary conditions (elevation, flow boundaries) and hydraulic properties (hydraulic conductivity). Bottom elevations for each cell were derived from the bedrock elevation map discussed earlier. Initial conditions for MODFLOW are also needed to solve the groundwater flow equation. MODFLOW uses the numerical solution for the partial differential equation of Darcy’s Law for each cell (McDonald and Harbaugh, 1988). The DEM was used to assign surface elevations as the starting heads for MODFLOW. This is a quick method of assigning starting heads along with the higher resolution inputs, as opposed to water wells, but it results in a longer initial simulation time to simulate heads from this initial estimate. A GIS coverage representing rivers was mapped over to the map module from the GIS module in GMS. Within the map module of GMS, editing was done to account for discrepancies where the river elevations from the DEM did not match those from the USGS Quadrangle digital raster graphic (DRG) for any given area. After the hydro coverage was edited to represent the Jordan River and its tributaries, elevations were assigned from the DRG where the Jordan River crossed elevation contours. An average stream channel bottom conductance was assigned. A stream width of 10 m was chosen as it was based on the average of all the cross section data collected at stream gage sites. A value of 30 m/d, a hydraulic conductivity value representative of sand and gravel (Freeze and Cherry, 1979; Schwartz and Zhang, 2003), was assumed for the conductivity of the river bed sediments. Thickness of river bed channel sediments was assumed to be 1 meter, limited to 27 the depth of the probing instrument. Equation 1 was then used to calculate the conductance for all segments of the river (i.e. arcs of the polyline file in GIS). The length of an arc is used by MODLFOW to assign conductance values in m2/d for each arc. C= w *k *l t (1.1) where; C is the conductance (L2/T) w is stream width (L) k is the hydraulic conductivity (L/T) of stream bottom sediments l is the length segment (L) t is the thickness of the stream bottom sediments (L). Recharge was estimated by choosing a value of stream flow from the USGS gage that represented base flow for the Jordan River. The value of base flow was then divided by the area of the groundwatershed for the USGS gage to estimate a steady-state recharge value. The groundwatershed of a specific point (i.e. the USGS gage) refers to the area from which all of the groundwater flows to that specific point. Only one groundwatershed was used because there was only one USGS gage available since 2007 that could be used to estimate recharge from base flow. Using the groundwatershed for the USGS gage resulted in a value of 0.001132 m/d for recharge, which is approximately 40 cm/yr. 28 The coverage representing the surface Quaternary geology of the area (Figure 1.8) was mapped from a GIS to the map module of GMS. An average hydraulic conductivity of 5 m/d was assigned as a starting value and average value for all the geologic zones, which vary from lucustrine sand to glacial outwash (Freeze and Cherry, 1979; Schwartz and Zhang, 2003). Parameter estimation was used to optimize hydraulic conductivity values for the main lithologic zones across the region. After allowing MODFLOW to run and converge on a solution, optimization was used to estimate the most important parameters within the groundwater model. Residential water well levels (Figure 1.9) for locations within the model area were plotted against simulated heads in those model cells. Preliminary ground water simulations were run separately for specific yield and hydraulic conductivity to test how of each of these hydraulic properties changed the simulated heads with respect to the observed heads. Simulations that only changed specific yield had little effect on the improving the differences between the observed and simulated head. However, simulations that changed only hydraulic conductivity improved the differences between the simulated and observed head thus only hydraulic conductivity was used in the optimization of the simulated heads. Four PEST (Parameter Estimation) simulations were run, within GMS, beginning with a hydraulic conductivity for all the geologic lithologies. Additional values of hydraulic conductivity were then added, starting with 2 and then 3, until the sum-square residual error between simulated and observed heads was no longer reduced (Table 1). Figure 1.12 shows a spatial 29 plot of heads and a graph of simulated versus observed heads for the best PEST simulation. Table 1.1: Values for hydraulic conductivity after optimization for geologic zones shown in Figure 8B. The starting hydraulic conductivity value for all the geologic zones for the optimization was 5 m/d. Geologic Zones Glacial outwash sand and gravel and postglacial alluvium Lucustrine sand and gravel Coarse-textured glacial till End moraines of coarse-textured till Hydraulic Conductivity (m/d) 6.34 1.12 0.55 2.81 A Figure 1.12: Simulated map of heads (A), along with a comparison between simulated vs. observed heads after PEST optimization (B). 30 400 Simulated Head (m) 350 300 250 200 y = 0.973x + 6.95 R² = 0.984 150 150 200 250 300 Observed head (m) 350 400 B Figure 1.12 continued The groundwatershed (Figure1.13) was drawn from the spatial plot of heads from the steady-state model (Figure 1.12) to represent the capture zone of the Jordan River system down to the headwaters of Lake Charlevoix. As discussed in the in the methods section, the southern boundary was drawn along a flow divide which was represented as a no-flow boundary. 31 Model Boundary Surface Watershed Boundary Ground Watershed Figure 1.13: Shows the JRW and groundwatershed (shaded) for the Jordan River within the model area. Transient Field Data Transient flow data collected from summer 2007 through fall 2008 were used to characterize the transient groundwater discharge and stream flow for the JRW. Flows were collected across the JRW to measure changes in channel geometry and flow for the Jordan River, and Deer Creek. Gages installed at three locations, two on the Jordan River and one on Deer Creek, provide nearly continuous estimates of stream flow to characterize the detailed transient hydrology in the drainage basin. The discharge from these gages combined with the USGS gage was used to analyze the stream flow response to precipitation and snow melt events in different reaches of the JRW. The gages at each site are pressure transducers that convert pressure created 32 from the water column above the transducer into water column height which represents the stage of the river. Stream discharge was measured at multiple stages and seasons, starting in 2007 and ending in 2008, for each site to create a stage-discharge relationship (Figure 1.14). An important assumption for these relationships is that the stream cross-channel geometry does not change over the period with which the data is collected. Stage-discharge relationships are commonly logarithmic because a river ultimately overflows its banks, reducing the effect of increasing stage on discharge. Ideally, a wide range of flow values would be available to establish this type of relationship, but the gage at Graves and Fisheries gages only have relatively low flows observed. Deer Creek has a well established stage-discharge relationship with stream flow observed from low to high values, being the gage with the best accuracy. High flow events have not yet been captured for the Jordan River because of the short lag between precipitation and peak flows, on the order of only a few hours. As a part of the flow measurements, cross channel geometry was measured at multiple sites, to characterize how stream flow and bed geometry changed across the watershed (Figure 1.15). Flow and bed geometry was also measured at the gage sites multiple times to see how bed channel geometry changed with time (Figure 1.16). These data indicate likely scouring between flow measurements at two of the gage sites, Deer Creek and Graves (Figure 1.16). 33 Deer Creek USGS 04127800 Fisheries Graves A Figure 1.14: Map showing gage locations within the Jordan River Watershed (highlighted in red) (A) along with their stage-discharge relationships: USGS Webster (B) Graves (C), Fisheries (D), and Deer (E). 34 700 Discharge (cfs) 600 500 400 300 y = 27.831e 1.904x 2 R = 0.893 200 100 0.8 1 1.2 1.4 1.6 1.8 Stage (m) B 170 Discharge (cfs) 160 150 140 y = 301.24x + 106.18 130 2 R = 0.336 120 110 0.06 0.08 0.1 0.12 Stage (m) C Figure 1.14 continued 35 0.14 0.16 0.18 75 70 Discharge (cfs) 65 60 55 y = 402.88x - 34.35 2 R = 0.905 50 45 40 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 Stage (m) D 180 160 140 Discharge (cfs) 120 100 80 y = 5.407e 60 5.606x 2 R = 0.992 40 20 0 0.2 0.3 0.4 0.5 Stage (m) E Figure 1.14 continued 36 0.6 0.7 Rogers Rd. Wesbter Br. Old State Rd. Graves Crossing Headwaters Penny Br. Position (m) 0 3 6 9 12 15 18 0 Depth (m) 0.2 0.4 0.6 Headwaters Penny Br. Graves Crossing Old State Rd. Webster Br. Rogers Rd. 0.8 1 1.2 Figure 1.15: Spatial channel cross channel geometries for all the sites where flows were conducted. 37 South 0 1 0 2 Position (m) 3 4 5 6 7 8 North 9 10 Depth (m) 0.1 0.2 0.3 0.4 0.5 A 0.6 07/01/07 09/01/07 09/17/07 04/11/08 07/06/08 09/29/08 Position (m) East 00 01/12/08 2 4 6 8 10 12 14 West 16 0.1 0.2 Depth (m) 0.3 0.4 0.5 0.6 0.7 0.8 B 0.9 Figure 1.16: Temporal cross channel geometry at Graves (A) and Deer Creek (B) gage locations. See Figure 1.14A for gage locations. 38 Through the course of this study flow from all the gages showed rapid response to precipitation events for Jordan River, while Deer Creek and the USGS Webster site can have relatively long lags of a few days (Figure 1.17). It should be noted that spike in precipitation around 8/6/07 is related to a rain gage malfunction (indicated by large precipitation events) on that date (NOAA, 2008). 400 0.4 300 0.8 200 1.2 100 1.6 2 Flow (cfs) Precipitation (inches) 0 8/6/07 8/6/07 8/6/07 8/6/07 8/6/07 8/6/07 8/6/07 Date 0 Precipitation NOAA Precipitation Gauge Flow Measured Flow USGS Webster Graves Fisheries Deer USGS Webster Graves Fisheries Deer Figure 1.17: Discharge at all four stream gages in response to Precipitation Events. Arrows indicate lags (MAWN, NCDC, and USGS). 39 Recharge Calculations for Land Cover It was important to characterize how recharge to the aquifer changed as a result of land cover. Several studies, previously mentioned, have been able to show how land cover affects groundwater recharge indirectly. Kendall (2009) used ILHM to simulate the direct effects of land cover on groundwater and stream flow in the Muskegon River groundwatershed. However, the development of an ILHM model, including gathering the necessary data, is very time intensive. Due to time constraints, a simplified approach that used precipitation-recharge ratios from ILHM was used to calculate recharge from the Jordan River precipitation data. Precipitation-recharge ratios allow an indirect estimate of how much precipitation in a given period becomes recharge. The calculation of the precipitation-recharge ratios accounts for sediment type (infiltration), and land cover (interception and evapotranspiration). The precipitation data set for the Muskegon drainage basin consisted of monthly precipitation for 27 years. ILHM then used the precipitation data for the Muskegon drainage basin to simulate monthly recharge for 27 years. In order to apply the precipitation-recharge ratios to the Jordan River precipitation data, a few steps were needed to estimate the ratios from the precipitation data and recharge simulated from ILHM. First, the effects of the snow pack accumulation and the large amount of melt that occurs in the Jordan River had to be examined. A simple way to simulate the effect of snow-pack accumulation in excel was to assign a constant-averaged value of precipitation to December, January, February, and March of every year. The constant-averaged value of precipitation 40 was calculated by summing all the precipitation for those 4 months in that year and then dividing by 4. The same value was then applied to all four months. The next step was to take the recharge simulated for the Muskegon Drainage basin by ILHM for a given month and divide by the precipitation for the Muskegon drainage basin for that same month. After all of the precipitation-recharge ratios were calculated for the 27 year data period, each value was averaged together to calculate monthly precipitation-recharge ratios that were independent of precipitation data. This process was repeated for each land cover type in the Anderson Classification System: open, agriculture, coniferous forest, deciduous forest, urban, and wetland. The precipitation-recharge ratios were then used to calculate recharge from the precipitation data for the model area. Monthly precipitation was used instead of hourly, daily, or weekly because of the lack of information and data that would be required to simulate of those time scales (i.e. evapotranspiration estimates). Monthly precipitation was multiplied by the precipitation-recharge ratio to calculate recharge for each month from January 1, 2007 through September 1, 2008. Due to the expected water repellent nature in soils after forest fires, an approach was developed to evaluate the effect of repellent soils that might have existed after forest fires, ultimately affecting the recharge. A runoff relationship which assumed high severity of burned soils (i.e. maximum WR), modified from Onda (2008), was used to evaluate runoff and infiltration for the simulation of post forest fire conditions in the model area. Onda studied the effects of runoff 41 after large storm events the season after a severe forest fire in terrain similar to the model area (steep slopes with sandy sediment), and devised devices that could measure runoff during rainfall events. The amount of runoff was then compared to the amount precipitation that a single rainfall event generated (Table 1.2). Table 1.2: Total rain and runoff data collected by Onda on hill slopes near Point Reyes, California immediately following a forest fire. This study used rainfall and runoff data to calculate runoff ratios which was the basis for the precipitationrunoff relationship. Values in red indicate the collection tank was full and did not actually record all the rain. Event 1 recorded 6.51 inches, but the actual rainfall was 7.96 inches. Event 6 recorded 1.43 inches but the total rainfall was 2.46 inches. Thus, 7.96 and 2.46 inches were used in the runoff-precipitation relationship. Modified from Onda (2008). Rainfall Event 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Total Rain (inches) 7.96 0.72 0.57 0.70 0.76 2.46 0.20 0.42 0.34 0.28 0.13 0.38 0.33 0.22 0.24 0.32 0.28 42 Runoff (inches) 0.74 0.44 0.17 0.24 0.21 0.74 0.04 0.15 0.27 0.09 0.02 0.06 0.04 0.07 0.09 0.02 0.04 Run off Ratio 0.19 0.62 0.3 0.35 0.27 0.52 0.18 0.36 0.81 0.32 0.17 0.16 0.12 0.31 0.37 0.07 0.15 The relationship from Onda (2008) was modified by removing rainfall events larger than 2.5 inches, as Jordan River receives considerably less in a rainfall event than the Point Reyes Peninsula in California where the study took place. The total rainfall versus runoff in Table 1.2 was then plotted relative to each other (Figure 1.18) to estimate a relationship between precipitation and runoff. The relationship was used to first filter out runoff from the precipitation data used in this study to simulate runoff in a post-forest fire land cover. The difference between daily rainfall and daily runoff was termed daily infiltration. The infiltration was then summed up for every month in the time-interval for this study (January 2007-September 2008). To estimate the amount of recharge from monthly infiltration, precipitation-recharge ratios from open land cover, based on ILHM, were used to simulate recharge for the post-forest fire land cover scenario. 43 0.8 0.7 Runoff (inches) 0.6 0.5 0.4 y = 0.244Ln(x) + 0.396 R2 = 0.771 0.3 0.2 0.1 0 0 0.5 1 1.5 Precipitation (inches) 2 2.5 Figure 1.18: Precipitation: Runoff relationship used to calculate infiltration and runoff. Modified from Onda (2008). Transient Model This model describes how base flow from groundwater changes as the land cover changes. Any alterations in the land cover change the percent of precipitation that becomes recharge. The transient groundwater model was developed by taking the head solution from the steady-state MODFLOW simulation and using it as the starting heads of the transient MODFLOW simulation. A general value of 0.2 was used as the specific yield for the near surface aquifer, as no data was available that would enable estimates for specific yield. Sensitivities were also analyzed by scaling different parameters. Two sensitivities scenarios were examined: 1) Decreasing the hydraulic conductivities by 50%, and 2) changing the specific 44 yield (S y ) from 0.2 to 0.35. Minimal sensitivity was found when increasing S y but all the simulated stream flows decreased significantly when hydraulic conductivities were decreased. For each land cover scenario, monthly recharge values were used as inputs into MODFLOW. The transient model was set up to run with monthly recharge, calculated from the precipitation data, from 01/01/07 through 09/01/08 so data from the four gages within the Jordan River could be used as observations. As a result, 21 stress periods were used with only 1 time step so that only monthly groundwater fluxes would be written out. A MATLAB script was then be used to read in the groundwater fluxes from MODFLOW to sum all the stream flow at all the gage locations within the JRW. 5 4.5 Recharge (inches/month) 4 3.5 3 2.5 2 1.5 1 0.5 0 01/01/07 04/11/07 Agriculture 07/20/07 10/28/07 Date Pre-developed 02/05/08 Current 05/15/08 08/23/08 Post Forest Fire Figure 1.19: Approximate recharge for estimated for different land cover scenarios within the model area. 45 Recharge for the land cover scenarios of interest: pre-developed (1800), post forest Fire (PFF), agriculture (AG), and current, where used as inputs into the transient MODFLOW model. Simulated base flow, calculated using the scripts and groundwater fluxes into the stream, was then matched with gage data. Because the transient model averaged recharge over the majority of the model area, the gage with the largest catchment, the USGS gage, was used for the observed stream flow. The simulated flow for the current land cover for the model area was plotted with the gage flow at the USGS Webster gage and base flow. The base flow was calculated using the local minimum base-flow separation method within the Web-based Hydrograph Analysis Tool (WHAT) (Lim et al., 2005) with a statistical comparison of the Eckhardt and BFLOW filter for 50 USGS gaging stations in Indiana. Lim et al., 2005, found a Nash-Sutcliffe coefficient over 0.91 for both filters applied to the data for all 50 gaging locations, concluding that WHAT will typically match most other traditional techniques that estimate base flow from stream flow. Matched base flow can lead to error, based on the method, where WHAT provides consistent results within minutes and is linked into the USGS gage server (Lim et al., 2008). 46 RESULTS AND DISCUSSION Model Results The simulated base flow for the current land cover within the model area provide a general representation of the base flow calculated from the USGS Webster gage using WHAT (Figure 1.20). Stream evaporation was not taken into account in the hydrologic simulations, which is part of the reason the simulated stream flow is higher than the base flow separated or gage stream flow. Other explanations for the simulated flow being higher than the observed stream flow are using a recharge for the model area that is greater than the catchment area for the USGS gage. Using MODFLOW, stream flow at the USGS Webster gage was simulated for the other land cover scenarios (Figure 1.21). 47 400 Discharge (cfs) 350 300 250 200 150 100 01/01/07 04/11/07 07/20/07 10/28/07 02/05/08 05/15/08 08/23/08 Date USGS Gage Flow Base Seperated Flow Simulated Flow Figure 1.20: Simulated Flow for Current Land cover within the Jordan River model area plotted with stream flow and base flow for the USGS Webster gage (USGS). 230 220 Discharge (CFS) 210 200 190 180 170 160 150 140 1/1/07 4/11/07 7/20/07 10/28/07 2/5/08 5/15/08 8/23/08 Date Current Landcover Post Forest Fire Agriculture Pre-developed Figure 1.21: Simulated stream flow at USGS Webster for all four tested landscapes. 48 The post forest fire landscape showed the most significant deviation in simulated stream flow from current land cover. The large difference in stream flow between the current and post forest fire landscapes is the result of the calculated runoff being added to the drainage basin from the method described in Onda (2008). This study appears to be the only documented use of this relationship, besides Onda, and this is only a gross estimate as such relationships are not readily transferable to other watersheds. Simulated stream flow for all the other landscapes (Ag, 1800) did not vary significantly from the current land cover scenario. Implications for Sediment Transport The ability to simulate stream flow was important to provide insights on how stream flow could have changed bed load transport. The stream flow affects the size of transported particles as well as the volume of sediment transported. Thus, a higher mean stream flow would have more capacity to transport sediment downstream (Figure 1.22). This is called potential and is controlled by the stream power, which is calculated using the following equation (Bagnold, 1966): ω= ρgdSu where; ρ is fluid density, g is the acceleration of gravity, 49 (1.2) d is flow depth, S is the energy gradient of the flow (stream gradient), and u is the mean velocity of the flow. Figure 1.22: Hjulstrom’s diagram showing velocities required for the entrainment and deposition of different sediment sizes. Modified from Prothero and Schwab (2004). The Jordan River clearly has the potential to transport sediment, thus there must be a source of sand that is supplying the sediment at high discharge events. Two of the most likely scenarios, for the JRW are landslides (due to steep slopes and deforestation) and runoff occurring soon after a forest fire. After examining the stream flow from different land cover scenarios, forest fires appear to be the most likely scenario to have large changes in stream flow and sediment transport within the JRW. Massive amounts of runoff and high 50 stream flow from large precipitation events after a forest fire could have delivered large loads of sediment to the river and throughout the drainage basin. The sediment left from the unusually high runoff and stream events could still be entrained at high stream flow and then transported at base flow. Unfortunately, runoff from the hydrophobic soils from the post-forest fire landscape was not directly evaluated as data within the region did not exist. 51 CONCLUSIONS A simple modeling approach using MODFLOW was used to simulate stream flow for the different land cover scenarios: pre-development, post-forest fire, agriculture, and current. These four land cover scenarios were chosen, based on the history of the area, to have the most potential impact on stream flow and sediment transport. The simulations over estimated stream flow relative to the USGS gage flow and base flow using base-flow separation. The resulting groundwater shed for the Jordan River was found to be about 30% larger than the drainage basin, making changes in land cover outside the drainage basin just as important as those within the basin. Simulations of changes within the past 150 years, such as deforestation, agriculture, and urbanization did not show significant change in stream flow. Although changing recharge via land cover alterations does not seem to have a large effect on the sediment transport of the Jordan River, runoff in the post-forest fire land cover did show the largest change in stream flow and thus a large change in sediment transport. The runoff generated from high precipitation events after a forest fire, along with impervious surfaces that have been added since forest fires (i.e. roads), could be significant enough to have added large amounts of sedimentation to the river which are still being transported today. 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Poff, N., Bledsoe, B., Cuhaciyan, C. “Hydrologic variation with land use across the contiguous United States: Geomorphic and ecological consequences for stream ecosystems.” Geomorphology 79 (2006) 264–285. Prothero, D., Schwab, F. Sedimentary Geology, W.H. Freeman and Company, 2004. Saito, H., Nakayama, D., Matsuyama, H. “Relationship between the initiation of a shallow landslide and rainfall intensity-duration thresholds in Japan.” Geoinformation 12 (2009) 487-495 Schuol, J., Abbaspour, K. “Using Monthly Weather Statistics to Generate Daily Data in a SWAT Model Application to West Africa.” Ecological Modeling 201 (2007) 301-311. Schwartz, F.W., Zhang, H., “Fundamentals of Groundwater.” John Wiley and Sons, Inc. New York, NY. (2003). Selle, B., Lischeid, G., Huwe, B. “Effective Modeling of Percolation at the Landscape Scale using Data-based Approaches.” Computers and Geosciences 34 (2008) 699-713. Sophocleous, M. “Groundwater recharge and sustainability in the High Plains aquifer in Kansas, USA.” Hydrology Journal 12 (2005) 351-365. 57 Sui, J., Karney, B. Fang, D. “Variation in water level under ice-jammed conditionfield investigation and experimental study.” Nordic Hydrology 36 (2005) 65-84. Thomas, A., Tellam, J. “Modeling of Recharge and Pollutant Fluxes to Urban Groundwaters.” Science of the Total Environment 360 (2006) 158-179. USGS Real-Time Water Data for the Nation. United States Geological Society. 2010. December 2008. < http://waterdata.usgs.gov/nwis/rt> Waterloo, M., Schellekens, J., Bruijnzeel, L., Rawaqa, T. “Changes in catchment runoff after harvesting and burning of a Pinus caribaea plantation in Viti Levu, Fiji.” Forest Ecology and Management 251 (2007) 31–44. Warnemuende, E., Patterson, J., Smith, D., Huang, C. “Effects of tilling no-till soil on losses of atrazine and glyphosate to runoff water under variable intensity simulated rainfall.” Soil & Tillage Research 95 (2007) 19-26. Wiley, M., Hyndman, D. Pijanowski, B.,Kendall, A., Riseng, C., Rutherford, E., Cheng, S., Carlson, M., Tyler, J., Stevenson, J., Steen, P., Richards, P., Steelbach, P., Koches, J., Rediske, R. “A multi-modeling approach to evaluating climate and land use change impacts in a Great Lakes River Basin.” Hydrobiologia 657 (2010) 243-262. Winkler, R., Spittlehouse, D., Golding, D. “Measured differences in snow accumulation and melt among clearcut, juvenile, and mature forests in southern British Columbia.” Hydrological Processes 19 (2005) 51-62. 58 CHAPTER 2: USING RADAR STRATIGRAPHY TO EXAMINE THE RESPONSE OF HISTORICAL SEDIMENT TRANSPORT TO LAND COVER ALTERATIONS 59 INTRODUCTION Landscape alterations through human disturbance can have a major effect on sediment accumulation in streams and rivers (Liebault et al., 2005; Noel et al., 2001; Lach and Wyzga, 2002; Kasai et al., 2005). Decisions about managing channels and slope erosion can be greatly improved if the link between sediment transport response and changes in both climate (i.e. precipitation) and human disturbance (i.e. land use) are clearly understood. Kasai et al. (2005) showed that major changes in sediment accumulation via deforestation altered channel morphology after aforestation occurred. In order to understand how climatic and anthropogenic forcing will affect sediment transport, the effects of climate and land cover on past sediment transport was evaluated. Dearing and Jones (2003) demonstrated the importance of knowing the sediment transport responses to climate and anthropogenic forcing. Deforestation and agricultural expansion can be a primary cause of changes in fluvial sediment transport rates, while climatic events play only a secondary role (Diodato, 2006). Foster et al. (2003) showed that over long time scales, landscape alterations by human disturbance can cause a larger shift in sediment movement within a stream, relative to climatic forcing. Syvitski and Milliman (2007) were able to correlate modeled changes in sediment yield due to landscape alterations, but their effort was limited by the need for higher resolution record of historic sediment transport behavior. 60 Deltas can provide detailed records of fluvial sediment transport dynamics, as sediments are eroded from the drainage basin and transported to the delta (Prothero and Schwab, 2004). If a specific volume of sediment within a delta can be dated, sediment transport rates and timing of deposition can be estimated. High resolution geophysical techniques, such as ground penetrating radar (GPR), can be a valuable tool for mapping deltaic structures. GPR can image variations in subsurface structure in the meter to centimeter scale (Knight, 2001), which is necessary to characterize deltaic structures. GPR has been used in a number of deltas (e.g., Jol and Smith, 1991) to map out 2-D and 3-D depositional structures that may then be correlated to changes in base-level (Bersezio et al., 2007) and fluvial geomorphology (Beres et al., 1999). Pelpoa and Hicken (2004) used GPR combined with sequences of historical aerial photographs to estimate sediment volume and mass flux rates over a 52 year period. The objective of this study is to characterize subsurface features related to fluvial or deltaic sedimentary environments using GPR. Another goal of this study is to provide information, such as locations of sediment types, and depths of different sediment layers to help estimate deposition chronology and sedimentation rates. The information from this study can also help estimate the total volume of sediment in the delta and historic sediment transport rates in the Jordan River. 61 Site Description The Jordan River (Figure 2.1) has likely undergone changes in position and sediment transport over the past 150 years due to changes in land cover, climate, and dredging of the channel between Lake Michigan and Lake Charlevoix in 1876 (Lake Charlevoix Association, 2008). Figure 2.1: The Jordan River Drainage basin is in the northern portion of Michigan’s Lower Peninsula (MIGDL). The dredging of the channel between Lake Michigan and Lake Charlevoix caused a drop in baselevel, which would have caused a change in the position of sediment deposition where the Jordan River flows into the lake. Before the channel was dredged in 1876, Lake Charlevoix level was approximately at 177.5 meters above sea level (Lake Charlevoix Association, 2008; see Figure 2.2). After the channel was fully dredged, the Lake Charlevoix level was equal to the level of Lake Michigan, and has since fluctuated due to changes in climate and 62 human activities. Figure 2.2B shows how the delta appears during periods of high and low lake levels. Lake level affects sediment deposition by changing the elevation where a velocity drop occurs, which causes it to drop much of its sediment load. When the water level for Lake Charlevoix was higher, prior to the dredging of the channel, the Jordan River would have reached near zero velocity at a point upstream from the current zone of deposition. 63 Figure 2.2: Lake Level data for the NOAA gage for Lake Michigan and Lake Huron. The dotted line shows the approximate level of Lake Charlevoix before the opening of the channel between Lake Michigan and Lake Charlevoix (NOAA). Lake levels are monthly averages. 64 Other disturbances that could have caused changes in the evolution of the delta are alterations to land cover during the late 1800’s and early 1900’s resulting from logging, forest fires, possible landslides, and agricultural development. Before geophysical measurements were conducted, the study area was surveyed with a Total Station at the origin of the grid (500, 500). Points that were not surveyed with the total station were surveyed manually by extending a measuring tape between the stakes that were previously surveyed with the total station. Then, additional stakes were placed every 20 meters until the northern section of the study area was surveyed. 26 lines were laid out along the northern section of the delta as shown in Figure 2.3. The section of the delta was chosen based on preliminary GPR data collected in the winter of 2007, where good reflection data was collected in the northern part of the survey area. 65 Figure 2.3: Study area showing GPR lines, auger boreholes, and Vibracoring locations adjacent to the Jordan River and Lake Charlevoix. The numbered locations will be referred to in the text (MIGDL). 66 METHODS Ground Penetrating Radar Ground Penetrating Radar (GPR) is a useful method for studying the geometry and relationships between certain stratigraphic facies (Jol and Smith, 1991). GPR works by sending electromagnetic (EM) waves from a transmitting antenna into the subsurface. These waves then reflect off interfaces between layers with contrasting dielectric properties and back to the receiving antenna, with some energy refracting into deeper layers. Electrical properties of soils and rocks are controlled by factors such as porosity, clay content, dissolved minerals, and water content (Beres and Haeni, 2000). The reflection of a wave can be described using the reflection coefficient, as mentioned by Davis and Annan (1988): R= Z 2 − Z1 Z 2 + Z1 (2.1) Z =( jωμ 1/ 2 ) σ + jωε ε = ε 0ε r (2.2) (2.3) where; Z is impedance ε 0 is the permittivity of a vacuum (8.85419x10-12 F/m) 67 ε r is the relative permittivity. σ is electrical conductivity (specified as a constant) Another control on the penetration of GPR reflections is the magnetic permeability of a material: μ = μ0 μ r (2.4) where; μ0 is the magnetic permeability of a vacuum (4 π x10-7 H/m) μr is the relative magnetic permeability. EM wave velocities can be used to estimate the depths for the GPR reflections and can help identify the material (Table 2.1) through which the waves propagated (Baker 1999). EM wave velocities can be calculated using: Vr = c (2.5) 1/ 2 (ε ) where; Vr is the EM propagation velocity of the media, ε is the dielectric constant, and c is the velocity of EM waves in a vacuum (3x108 m/s). 68 Table 2.1: Various materials and their relative permittivity and velocity, Modified from Baker (1991). Materials Relative Permittivity Velocity (ft/ns) Velocity (m/ns) Fresh Water 80 0.11 0.03 Soil, sandy wet 15-30 0.18-0.25 0.05-0.08 Sand, wet 20-30 0.18-0.31 0.05-0.09 Silts 5-30 0.18-0.44 0.05-0.13 Clays 5-40 0.16-0.44 0.05-0.13 Clay, wet 15-40 0.16-0.25 0.05-0.13 Soil, loamy wet 10-20 0.22-0.31 0.07-0.09 Soil, clayey wet 10-15 0.25-0.31 0.08-0.09 Shales 5-15 0.25-0.44 0.08-0.13 Snow 80 0.28-0.35 0.09-0.11 Soil, sandy dry 4-6 0.40-0.49 0.12-0.15 Soil, loamy dry 4-6 0.40-0.49 0.12-0.15 Soil, clayey dry 4-6 0.40-0.49 0.12-0.15 Sand, dry 3-5 0.40-0.57 0.12-0.17 Clay, dry 2-6 0.40-0.70 0.12-0.21 Fresh Water Ice 3-4 0.49-0.57 0.15-0.17 Air 1 0.98 0.30 GPR Data Collection The GPR data was collected in March 2008, with 163 files over 38 lines. This GPR data was collected in the winter as a hard snow pack covers up uneven terrain, leaving a flat surface to collect GPR, and we could collect data over the water and other areas that are normally only accessible by boat. The data was collected by pulling a pair of 200MHz bistatic antennas mounted on a sled behind a snowmobile (Figure 2.4). The 200 MHz frequency was based on preliminary GPR data collected in the winter of 2007 where 100 and 200 MHz antennas were tested The 200 MHz data showed more contrast in the subsurface reflections than the 100 MHz data. 69 The system was triggered every 10 cm by a wheel that followed the sled. Due to the low friction surface of the snow pack, wheel slip occurred. This was accounted for by marking traces during data collection when the center of the antenna array is at marked stakes in the field. The locations were then corrected using a processing step called “rubbersheeting”. Some lines through thick vegetation were collected manually by holding the bistatic-antenna at a fixed distance of 50 cm. Data was collected using a 200 ns time window with 32 stacks and a 0.01 meter step size. Figure 2.4: GPR antenna setup during data acquisition in the winter of 2008. Photo by Christopher L. May. 70 GPR Processing After GPR data were collected, processing was done to remove artifacts in the data and to calculate depths so the data can be analyzed and interpreted. REFLEX was used for all the processing as described in Figure 2.5. Figure 2.5: GPR processing algorithm. Arrows indicate the progressive processing steps applied to the GPR data. 71 After importing the data into REFLEX, a 1-D Dewow filter (moving-average filter in z direction) was applied to all the GPR data profiles. Rubbersheeting was then used on all the GPR traces to move traces to more accurate locations. The zero time for the GPR data was chosen to be after the direct air waves, effectively removing these waves from the data. A series of 1-D and 2-D filters were applied to the GPR data to reduce noise. Background filtering was applied to all of the GPR data, before files were merged. Band pass, deconvolution, and average subtraction filters were then applied after merging. After data sets were merged and filtered to isolate good reflectors, a velocity was assigned to the GPR data to evaluate depths of reflectors. The average velocity used for all 26 GPR lines was 0.06 m/ns, which is representative for wet sand (Table 2.1). Auguring In the summer of 2008 the sediments across the study area were characterized using peat and bucket sampling augers. Several of the auger locations were selected on GPR line intersections to help link the GPR reflectors to the site stratigraphy (Figure 2.3). Most auguring locations were chosen to delineate zones where sand was deposited. For this purpose, a peat sampler with an extension rod, both measuring 1 meter in length, were used. The 1st meter of the auger was pushed in the ground sampling just the top meter. Notes were taken on “feeling/sound” for clay or sand, and then these steps would be 72 repeated for the 2nd meter. Any material recovered in the top two meters was described and sampled. Five detailed boreholes drilled in a northwest-southeast transect perpendicular to the river and boreholes north of Sportsman’s Park were used as a control on the spatial variation of sand outside the GPR grid (Figure 2.3). Other detailed borehole logs were conducted to characterize the stratigraphy in the vicinity of the GPR grid. The contact between the bottom clays and the sand were difficult to characterize, as the augers disturbed the sediment to the point that it become difficult to decipher the contact. This uncertainty in the horizon locations complicates the linkage between the borehole data and the GPR profiles. 73 RESULTS AND DISCUSSION Borehole Data Sand was observed at borehole locations in the northwestern section of the delta on both sides of the river. The thickness of the sand varied between 1 and 2 meters, and varied between fine-coarse sand, sometimes with abundant organic material (Figure 2.6). The material below the sand is generally peaty or mucky clay, likely of lucustrine origin. Silt was observed in some locations but was not as abundant as the clay. In locations where no sand was found, the peaty and mucky clay extended from the surface to at least 4 m depth. There was abundant organic matter in all borehole cores, which mostly started between 0.75-1 meter depths. The organic matter was often present with sand, which was logged as organic sand. The organic material primarily consisted of reeds and woody debris, and seeds were present in some samples. Calcareous shells were present in all the boreholes between 0.8 and 1 m. In boreholes where the contact existed, the contact between the sand and the clay was often gradational with finer sediments at depth. 74 Figure 2.6: Borehole data collected in the summer of 2007. All surface sediment was a very thin (<1cm) layer of organics from current riparian vegetation and was excluded from this graph. Boreholes are highlighted in Figure 2.3. 75 GPR Signatures The GPR data was attenuated to the point where only a few significant reflectors could be identified and interpreted. The degraded data quality could have been from various reasons such as the antenna being close to the snowmobile, rapid mode of data acquisition, high organic matter content, and diffractions from roots of the vegetation. Out of all the GPR data, 5 GPR lines were chosen, based on data quality, for interpretation (Figure 2.7). Two types of reflectors are observed in the GPR data. The first can be characterized as smooth low angle-concave up reflectors, while the second dip toward the north and northwest. Most of the first types are concave-up reflectors that occur in the East-West GPR profiles, roughly parallel to the current channel of the Jordan River and are within 2 m of the ground surface and dips toward the north and northwest (Figure 2.8). The second type of reflector (Figure 2.9) occurs at depths between 1 m to 3 m and occurs as smooth low angle-concave up reflectors. 76 Figure 2.7: A) Raw 2-D GPR data profiles shown with line numbers that correspond to the GPR grid shown in Figure 2.3. Letters S, C, and M represent sand, clay, and muck respectively, found in cores that coincided with GPR lines. 77 Figure 2.8: GPR profiles shown with 1 type of interpretation (light blue lines). 78 Figure 2.9: GPR profiles with interpretations of concave-up reflectors (red lines). 79 GPR Interpretation Some of the sand-clay/muck contacts align with reflectors that indicate a fluvial sedimentary environment. The interpreted concave-up reflectors (Figure 2.9) can be related to paleo-channels that have been scoured out by the stream and then filled in with new material (i.e. sand). The dipping reflectors in the EastWest GPR profiles of Figure 2.9 could result from a migrating point bar, with sand deposition, as the Jordan River has changed positions over time. The dipping reflectors in the South-North GPR profiles in Figure 2.8 could be formed by the deposition of sand at higher Lake Charlevoix water levels. The dipping structures representing foresets created in delta environments when sediment (i.e. sand) is being transported in the Jordan River is deposited when its velocities drop at the entrance to Lake Charlevoix. Current GPR data and borehole data are suggestive of fluvial and deltaic environments but due to certain limitations the results are not yet conclusive. Attenuated GPR signals made data interpretation very difficult, so only 5 lines were used to describe the stratigraphy of the study area. No GPR velocity measurements were collected, reducing the accuracy of reflector depths. The snow pack thickness was not accounted for during GPR data processing. Also, error could have also been introduced when comparing borehole data and GPR data as the GPR was collected on top of the snow and the boreholes were augured from the ground surface. During auguring, undisturbed sediment could not be recovered which introduced significant uncertainty in the elevation link between borehole data and GPR data. 80 CONCLUSIONS GPR was effective for visualizing sediment distributions within the study area. Borehole data showed a gradational boundary between clay and sand, while GPR reflectors provided insights into the 2D geometry of sediment. Borehole data aided in the interpretation of the GPR data as either deltaic or fluvial, but no conclusion could be made about the detailed sedimentary environment. Potential future work could include conducting GPR surveys on the other side of the river where sand was observed in boreholes. GPR data could be collected at the southern end the study area to see if prominent reflectors are observed. Marine seismic and sonar bathymetry for offshore geophysics, combined with GPR on land, would provide more accurate estimates of the total volume of sand that has been deposited, although dreaded volumes would have to be included. 81 BIBLIOGRAPHY 82 Baker, P. “Response of Ground-penetrating Radar to Bounding Surfaces and Lithofacies Variations in Sand Barrier Sequences.” Exploration Geophysics 22 (1991): 19-22. Baker, G. “Seismic imaging shallower than three meters” Diss. U of Kansas. 1999. Beres, M., Haeni, F. “Application of ground-penetrating-radar methods in hydrogeologic studies.” Groundwater 29 (2000): 375-386. Beres, M., Huggenberger, P., Green, A., Horstmeyer, H. “Using two- and threedimensional georadar methods to characterize glaciofluvial architecture.” Sedimentary Geology 129 (1999) 1–24. Bersezio, R., Giudici, M., Mele, M. “Combining sedimentological and geophysical data for high-resolution 3-D mapping of fluvial architectural elements in the Quaternary Po plain (Italy).” Sedimentary Geology 202 (2007) 230–248. Davis, J., Annan, A. “Ground-penetrating radar high-resolution mapping of soil and rock stratigraphy.” Geophysical Prospecting 37 (1988) 531–551. Dearing, J., Jones, R. “Coupling temporal and spatial dimensions of global sediment flux through lake and marine sediment records.” Global and Planetary Change 39 (2003) 147–168. Diodato, N. “Modelling net erosion responses to enviroclimatic changes recorded upon multisecular timescales.” Geomorphology 80 (2006) 164–177. Foster, G., Dearing, J., Jones, R., Crook, D., Siddle, D., Harvey, A., James, P., Appleby, P., Thompson, R., Nicholson, J., Loizeau, J. “Meteorological and land use controls on past and present hydro-geomorphic processes in the pre-alpine environment: an integrated lake–catchment study at the Petit Lac d’Annecy, France.” Hydrological Processes 17 (2003), 3287–3305. Great Lakes Environmental Research Laboratory. National Oceanic and Atmospheric Administration. 2010. January 2008 Jol, H., Smith, D. “Ground Penetrating Radar of Northern Lacustine Deltas.” Canadian Journal of Earth Science 28 (1991) 1939-1947. Kasai, M., Brierley, G., Page, M., Marutani, Tomomi, M., Trustrum, N. “Impacts of land use change on patterns of sediment flux in Weraamaia catchment, New Zealand.” Catena 64 (2005) 27–60. 83 Knight, R. “Ground Penetrating Radar for Environmental Applications.” Annu. Rev. Earth Planet. Sci. 29 (2001) 229–55. Lach, J., Wyzga, B. “Channel Incision and Flow Increase of the Upper Wisloka River, Southern Poland, Subsequent to the Reafforestation of its Catchment.” Earth Surface Processes and Landforms 27 (2002) 445-462. The Lake Charlevoix Association. 2008 . Liebault, F., Gomez, B., Page, M., Marden, M., Peacook, D., Richard, D., “Trotter, C.M. Land-use Change, Sediment Production and Channel Response in Upland Regions.” River Research and Applications 21 (2005) 739-756. Michigan Geogrpahic Data Library. State of Michigan. 2010. 1 December 2008 < http://www.mcgi.state.mi.us/MIGDL/> Nichol, S., Lian, O., Horrocks, M., Goff, J. “Holocene record of gradual, catastrophic, and human-influenced sedimentation from a backbarrier wetland, northern New Zealand.” Journal of Coastal Research 23 (2007) 605-617. Noel, H., Garbolino, E., Brauer, A., Lallier-Verges, E., Beaulieu, J., Disnar, J. “Human impact and soil erosion during the last 5000 yrs as recorded in lacustrine sedimentary organic matter at Lac d’Annecy, the French Alps. Journal of Paleolimnology 25 (2001) 229-244. Pelpoa, C., Hickin, E. “Long-term bed load transport rate based on aerial-photo and ground penetrating radar surveys of fan-delta growth, Coast Mountains, British Columbia.” Geomorphology 57 (2004) 169–181. Prothero, D., Schwab, F. Sedimentary Geology, W.H. Freeman and Company, 2004. Syvitski, J., Milliman, J. “Geology, Geography, and Humans Battle for Dominance over the Delivery of Fluvial Sediment to the Coastal Ocean.” The Journal of Geology, 115 (2007) 1–19. Wallinga, J., Davids, F., Dijkmans. “Luminescence dating of Netherlands’ sediments.” Netherlands Journal of Geosciences 86 (2007) 179-196. 84 CHAPTER 3: EVALUATING THE INFLUENCE OF LAND COVER ON NUTRIENT TRANSPORT AND IN-STREAM NUTRIENT PROCESSING 85 INTRODUCTION Different land uses can leach nutrients into groundwater which then flows out to streams. Degraded water quality can lead to eutrophication of surface waters and algal blooms (Heisler et al., 2008), and can cause stress for fish and other aquatic species (Klingeman et al., 1998). Biogeochemistry is affected as humans alter the natural landscape, mainly through urbanization and agricultural development (Fitzpatrick et al, 2007). It is important to understand how nutrient inputs from land cover are transported to streams through groundwater fluxes. Nutrient loading into streams been extensively studied over the last few decades (e.g., Reckhow and Chapra, 1999; and Boutt et al., 2001). Cabana and Ramussen (1996) found an increase in the delta 15 nitrogen isotope levels of primary consumers as human density increased; though no specific relationships between land use practices and nitrogen isotopes in biota could be established. However, positive correlations have been found between nitrogen isotope levels and increases in percentages of suburban, and agricultural land cover (Vander Zanden et al., 2005). Although correlations can help provide information where nutrient sources come from, the transport mechanisms for nutrients between sources and sinks need to be understood. Reckhow and Chapra (1999) points out that advances in models can provide understanding in the transport mechanisms for nutrients, which need to be combined with observations. Groundwater models and 86 geographic information systems (GIS) have provided additional tools to help identify sources of nutrient loading into streams (Boutt et al., 2001). Nitrate is a common groundwater pollutant with fertilizer and septic tanks being common sources to near-surface aquifers (McMahon et al., 2008). Nitrate inputs from urban landscapes are commonly believed to be smaller than from agricultural areas (Nolan and Stoner, 2000). However, outputs from sewage treatment plants and fertilizers from urban land cover have higher concentrations than other land covers (Fitzpatrick et al., 2007; Close, 1989). Puckett et al. (2008) found that short groundwater residence times can be linked to increased in-stream nitrate concentrations. Phosphorous transport through groundwater can be an important source of nutrient loading to streams. The major source of phosphorous in streams is generally considered to be associated with overland flow from the adjacent land surface (Carpenter et al., 1998). McCobb et al. (2003) and Chardon et al. (2007) found TDP concentrations greater than 10 mg/L in sandy soils leached from manure piles and cow pastures. More information is needed about loading of phosphorous to streams from groundwater to reduce water quality degradation. Waschbusch et al. (1995) conducted a water quality study in two suburban areas and found TDP concentrations of 0.61 mg/L due to leaching from lawns. Observed values of TDP leached from manure piles have ranged from 0.80-10 mg/L (McDowel and Sharpley, 2001). Drainage from septic systems can also provide a significant 87 source of TDP to groundwater as discussed in Arnscheidt (2007) and Fitzpatrick et al. (2007). The transport of nitrate and TDP through the groundwater can be significantly different. In fact, previous research generally considered surface runoff to be the only contribution of total phosphorous (TP) to streams (Sims et al., 1998). Tesoriero et al. (2009), across 5 drainage basins in the continental U.S. (all with poorly drained surface soils),found that nitrate loading into streams increased proportionally to the base flow index (BFI), while there was no significant increase in orthophosphate with high values of BFI. However, various forms of phosphorous have been shown to be transported into shallow groundwater, especially the forms dissolved phosphorus which is combined together into TDP in this paper (Sims et al., 1998). Adriano et al. (1975) found phosphorus levels greater than 0.92 mg/L at 6.6 meters depth in sandy soils. Numerous studies have reported groundwater concentrations of TP greater than 1.0 mg/L, which exceeded most surface water quality standards (Breesuswma et al., 1995). Another factor contributing to the transport of TDP in the groundwater is sediment characteristics. Vanek (1993) concluded that sand higher in calcium retained more TDP than sand with lower or calcium content. Deep-Siliceous sands have been found to be a significant source of TDP transported in groundwater to streams (Sims et al., 1998). MODFLOW (Harbaugh et al., 2000) and MT3D (A Modular 3-D MultiSpecies Transport Model, Zheng, 2006) have been used to simulate nitrate concentrations through groundwater with simple non-reactive transport (Almasri 88 and Kaluarchchi, 2007). Lerner and Papatolios (1993) used a simpler approach to predict groundwater nitrogen concentrations, assuming uniform recharge, to calculate input concentrations. The objective of this study is to illustrate how multiple land covers can be superimposed to identify potential sources of nutrient loading for nitrate and TDP. This study incorporates the use of groundwater and nutrient transport models combined with a 1-D description for nutrient uptake for the Sycamore Creek Watershed in southern Michigan. Site Description The different land cover types that Sycamore and Mud Creeks flow through make the SCW a good study site for testing nutrient inputs from different land cover types. Current land cover in the Sycamore Creek Watershed (SCW) varies from forest to agriculture and urban areas. In the SCW, the winter-snow and fall storms sustain perennial streams via groundwater flow. Coupled with anthropogenic land use practices and perennial streams fed by groundwater, nutrient loading from groundwater into streams is an important concern to investigate. Modeling groundwater transport of nutrients to streams can provide a powerful tool to improve the understanding of impacts of different land covers to surface water quality. Modeling groundwater transport requires knowledge of groundwater flow based on sediment properties, climate inputs, and sources and sinks of an area. The Grand River, along with some of its tributaries, makes up the southern and 89 western edges of the model boundary, and the Red Cedar River and its tributaries form the eastern and northern edges of the model boundary (Figure 3.1). It was important to expand the model boundaries to appropriately define the area of groundwater capture to the stream system, called the groundwatershed, as described by Boutt (2001). The groundwatershed (280 km2) and the surface watershed (275 km2) for Sycamore and Mud Creeks are similar, thus only the watershed will be discussed from this point on. Lansing Red Cedar River Mud Creek Grand River Sycamore Creek Mason Figure 3.1: The model area along with Sycamore Creek Watershed (SCW, highlighted in pink) is located in South Central Michigan (from MIGDL). 90 Source and Sinks Agricultural and urban areas are the two dominant land use types within the SCW, thus these types represent the two most likely sources for nitrate and TDP. Agricultural sources of nitrate and TDP include leachate from application of manure and fertilizer to crops and fields, manure piles from pastures (defined as Herbaceous Rangeland in the Michigan Geographic Data Library (MIGDL)), and CFOs (Confined Feeding Operations). Urban sources of nitrate and TDP include application of fertilizers to lawns and inputs from septic tanks and sewers. The headwaters of Sycamore and Mud Creeks both start in agricultural areas and then merge just after passing the city of Mason, which is a small rural community (Figure 3.2). At the lower end of the drainage basin, Sycamore Creek flows through highly residential and industrial zones just before flowing into the Red Cedar River. 91 Figure 3.2: Map of Current Land cover for the Sycamore Creek model area (MIGDL). 92 METHODS GIS Data Modeling groundwater flow and transport across drainage basin scales requires large data sets that describe the physical nature of the study area such as topography, aquifer geometry, and geology. A 9-m DEM (Digital Elevation Model) was used for topography (Figure 3.3) from NED (the National Elevation Data set), which was created from aerial and topographic maps that represent bare earth. The DEM provides detailed information about the top of the near surface aquifer in which nitrate and TDP transport is simulated. The most important use of the DEM in this study was to assign stream elevations to Sycamore and Mud Creeks along the entire drainage system. 93 Figure 3.3: A 9 meter resolution DEM plotted with the model area (bold outline) and the SCW (light outline) (SEAMLESS). A GIS based Quaternary Geology map developed by Farrand and Bell (1982) was used as a framework for hydraulic conductivity zonation in the MODFLOW model (Figure 3.4). This glacial drift aquifer mainly consists of medium-textured till and end moraines with some glacial outwash deposits. 94 End moraines of medium-textured till Glacial outwash sand and gravel and postglacial alluvium Medium-textured till 0 km 2.5 5 10 Figure 3.4: Surficial Quaternary Geologic Map used for geologic facies description for MODFLOW and MT3D (Farrand and Bell, 1982). Observed groundwater levels, aquifer geometry, and septic tank locations were created from a single water well coverage (Figure 3.5). Insufficient oil and gas wells were available in the model area to provide sufficient information. The well data set is digitized from residential wells in Ingham and Eaton Counties from MIGDL. All the wells were first filtered on the basis of locations and elevations. In ArcGIS, the DEM elevation was extracted for each well and then compared with the values recorded by well drillers. If the absolute difference between these two values is greater than 1 meter, the well is excluded from further analysis. Wells that were clearly mislocated (i.e. wells located outside of Ingham and Eaton Counties despite being labeled as in the county) were also removed. Wells that had major discrepancies such as negative bedrock elevations were also removed, as this is out of the range of known elevations. 95 Additional filtering for observed heads was based on casing depth, type of aquifer, and recorded static water level (SWL). Observations were not used from wells if the casing depth (bottom of the well) was below the elevation of the aquifer bottom or if the recorded aquifer material was consolidated rock. Because most of the wells in the model area are located in the Saginaw Formation (a major aquifer for Michigan), only 42 out of 300 wells could be used for water level comparisons with the MODFLOW simulation. Wells used for simulating Septic inputs into ground water and for creating the bedrock surface Observatation Wells 0 2.5 5 km 10 Figure 3.5: Wells used to construct the map of the aquifer bottom, for water level observations, and to provide septic well inputs. Wells used inside the model boundary (yellow line) were used to simulate nutrient inputs from septic systems (MIGDL). 96 Most of the residential wells in the model area pump their water from the Saginaw Aquifer, a major confined aquifer across much of Michigan. The casing depths of these wells make them suitable to build the bedrock elevation map to represent the bottom of the glacial drift aquifer that is the focus of this study. Bedrock wells inside and outside the model boundary were selected, and bedrock depths for these wells were chosen where the well intersects the top of a confining formation (i.e. the Marshall Formation or Jurassic red beds that are shale units). Clear outliers in the data were removed from the data set if the bedrock elevation varied more than 40-60 meters from surrounding bedrock elevations. Using this methodology, 41 outliers were removed. The bedrock elevations were then interpolated using ordinary kriging in ARCGIS using a circular variogram model (Figure 3.6A) after removing 1st order trend. Variogram modeling parameters included 164.14 nugget, 100 m lag size, 12 lags, and a partial sill of 100.46. After removing outliers, the interpolated surface was converted to a grid with a 20 m cells (Figure 3.6B). 97 Semi-variance*10^-2 3.1 2.48 1.86 1.24 0.62 0 0 150 300 450 600 750 900 1050 1200 Distance, h (m) A 275 m 200 m 0 2.5 5 km 10 B Figure 3.6: Variogram model (using a Circular model, 255 m range, 164.14 nugget, 100 sill, 100 m lag size, 12 lags, and no anisotropy) (A) incorporated into the interpolation of the bedrock elevation map (B). 98 Steady-state Model The boundary conditions for the groundwater model were assigned from the DEM, bottom geometry map, stream coverage, and model boundary. The top elevations for the groundwater model were assigned from the DEM. The bottom elevations for the ground water model were assigned from the bedrock elevation map presented in Figure 3.6. Starting heads were initially estimated using the DEM elevations. After running a preliminary model, the head solution was exported and used as the starting heads for future models. The streams were generated from the DEM in Arc by creating flow direction and flow accumulation grids, which were then used to calculate flow length and stream order metrics. Once the artificial stream network was created, the elevations from the DEM were used for stream elevations. Along with drain elevations, conductance values (L2/T) were assigned to each arc. The conductance was calculated as the stream width multiplied by the hydraulic conductivity of stream bottom sediments times the stream segment length, divided by the thickness of the stream bottom sediments. GMS automatically calculated the stream lengths using the information mapped over from the GIS streams coverage. An average width of 10 m was estimated from field data. A representative hydraulic conductivity of 2 m/d was used for the sediment hydraulic conductivity for Sycamore and Mud Creeks. The thickness of the bottom sediments was assumed to be 1 meter for all drain cells. Another important step in the development of a groundwater model is assignment of recharge across the model area. An initial recharge value of 22 99 cm/yr was estimated based on stream flow data from a USGS gage station at Holt road, which was removed in 1997. The minimum recharge estimate was calculated by dividing base flow measured in August 2007 by the area of the groundwatershed for the USGS gage. Leakage between the near surface glacial aquifer and the underlying Saginaw aquifer was not calculated because most of the model region has a significant confining bed thickness between the aquifers. Since no hydraulic conductivity data are available from pump tests and slug tests within the model area, a single value of hydraulic conductivity (5 m/d) was used as a starting value for all of the geologic zones (Freeze and Cherry, 1979; Schwartz and Zhang, 2003). The hydraulic conductivities for the main geologic zones were then optimized using the PEST parameter estimation code. The measured SWLs from the GIS well coverage were used as observed heads to be compared to simulated heads from MODFLOW (Figure 3.5). One hydraulic conductivity value for the model area was optimized to obtain the minimum residual error between the simulated and observed heads. Parameter optimizations for two or three geologic zones did not result in a significant reduction in residuals, thus only one value hydraulic conductivity, optimized to 6.44 m/d, was used for all glacial deposits. Figure 3.7 shows observed vs. simulated heads along with a spatial plot of the final head solution. Simulated stream flow was extracted from the model results using a script and compared against stream flows that we measured at or near base flow. Only 1 measured flow in this study, located at Aurelius, matched well (Table 3.1). The Aurelius site 100 matched well because the recharge for this site was calculated based on the baseflow for this station. Table 3.1: Simulated flow and averaged measured flow at three locations Simulated Head (m) 295 285 275 265 y = 0.946x + 14.91 255 245 245 2 R = 0.9281 255 265 275 285 295 Observed Head (m) Figure 3.7: Simulated heads plotted relative to observed heads (A) and mapped (B). 101 Head (m) 295 250 0 2.5 5 km 10 Figure 3.7 Continued Groundwater transport using MT3D Possible sources of nutrients observed during base flow are septic tank inputs and leaching from agriculture, pasture, and urban landscapes. We examined the potential inputs of each of these main potential sources by simulating each land use derived source in a separate transport models then superimposing these into one solution. This allows the influence of each land use on water quality to be examined. 102 The benefit of simulating separate land cover types is that solutions from the transport models can be superimposed to evaluate the effects of multiple land uses and to estimate input concentrations, using optimization. For each dominant land cover, unit concentrations (1 mg/L) were assigned for both Nitrate and TDP. Residential wells within the model boundary were selected to be septic sources (Figure 3.5). It was assumed that a septic input existed for each residential water well because the residential water wells exist in rural areas where city sewer systems did not exist. The unit concentration for the septic tanks was applied to a volumetric flux of 3 m3/day, which was the estimated water usage per household of four people (Elmwood, 2008). Polygons of agriculture, herbaceous pasture, and urban land covers were used to assign the starting concentrations for Nitrate and TDP. The concentrations were applied to the recharge flux (22 cm/yr) as recharge concentrations. When simulating groundwater transport on any scale, values for dispersion and porosity are usually unavailable, unless derived from empirical measures, thus representative values were chosen. The ratios of transverse to longitudinal dispersion were selected as 500, 1E-4 m2/d for the molecular diffusion coefficient, and 5 m was used as for the longitudinal dispersitivty (Freeze and Cherry, 1979). A representative value for porosity of 0.3 was assigned for all geologic zones. Nitrate and TDP in this study are assumed to be mobile, thus the nutrient transport is mainly by advection. The advection part of the transport equation used by MT3D is solved using the Hybrid Method of Characteristics (HMOC) 103 which combines the Modified Method of Characteristics (a backward particle tracking scheme) and the Method of Characteristics (a scheme that tracks multiple particles forward in time). It is important to note that assuming mobile species is a significant simplification for simulating groundwater fluxes to streams, especially for the transport of TDP which can bind to iron oxides on sediments. Observed mass fluxes and total nutrient concentrations for Sycamore and Mud Creeks were calculated using measured stream flow and in-stream concentrations (Figure 3.8) during base flow conditions in the summer of 2005, as described in Welty (2005). After starting concentrations and values for the dispersion and advection packages were assigned, the four transport simulations for septic inputs, agriculture, pasture, and urban landscapes were run for 150 years to account for the main period of anthropogenic settlement (Dickmann and Leefers, 2004), based on the steady-state flows from MODFLOW. Water fluxes from MODFLOW were multiplied by concentrations from MT3D to calculate nutrient mass fluxes on a cell by cell basis. Measured and simulated concentrations (mg/L) and stream flows (m3/s) for each site were multiplied together to calculate the mass fluxes (mg/s). 104 2000.0 2000.0 1800.0 1600.0 1400.0 1200.0 1000.0 800.0 600.0 400.0 200.0 0.0 1500.0 1000.0 500.0 0.0 Nitrate Differential Flux (mg/s) Nitrate Total Flux (mg/s) Sycamore Creek -500.0 0.592 3.287 11.701 17.235 26.34 29.226 33.15 Distance Downstream (km) Total Nitrate Flux Differential Nitrate Flux Mud Creek 80.0 100.0 60.0 80.0 40.0 60.0 20.0 40.0 0.0 20.0 0.0 -20.0 0.836 A 6.34 10.238 14.512 19.946 Distance Downstream (km) Figure 3.8: A) Nitrate observations, B) TP observations (Welty, 2005). 105 Nitrate Differential Flux (mg/s) 100.0 120.0 Nitrate Total Flux (mg/s) 140.0 Sycamore Creek 40.0 80.0 30.0 60.0 20.0 50.0 40.0 10.0 30.0 0.0 20.0 -10.0 10.0 0.0 TP Differential Flux (mg/s) TP Total Flux (mg/s) 70.0 -20.0 0.592 3.287 11.701 17.235 26.34 29.226 33.15 Distance Downstream (km) Total TP Flux Differential TP Flux Mud Creek 7.0 8.0 6.0 7.0 5.0 6.0 4.0 5.0 3.0 4.0 2.0 3.0 2.0 1.0 1.0 0.0 0.0 -1.0 0.836 B 6.34 10.238 14.512 19.946 Distance Downstream (km) Figure 3.8 Continued 106 TP Differential Flux (mg/s) 8.0 9.0 TP Total Flux (mg/s) 10.0 Optimization using a simple 1-D In-stream Processing Description This study assumes that nutrient loading into streams from groundwater can be linearly superimposed based on separate land cover based subsurface inputs. Equation 3.1 was used to minimize the sum of absolute residuals between measured and simulated fluxes by adjusting scaling coefficients for each land use type. MIN{SUM(ABS((aAg+bU+cS+dR-rL+MWTP)-Obs))} (3.1) where a, b, c, d = coefficients representing starting concentrations to be estimated (mg/L). Ag, U, S, and R = simulated unit fluxes (total or differential) from Agriculture, Urban, Septic, and Pasture (mg/s). r = processing rate of nutrients by length of stream along palustrine wetlands (mg/s/m) L = length of palustrine wetlands connected to the stream (m). MWTP = Calibrated mass flux for the Mason Waste Water Treatment Plant (mg/s) This superposition approach could be used with multiple land use types due to linearity of the concentrations for a stream that effectively accumulates flow and associated solutes from multiple land use sources. Excel Solver was used for the optimizations using equation 3.1. A description of in-stream processing is included to account for the observed negative differential nutrient concentrations (Figure 3.8), which is assumed to be due to wetland processing, 107 including biological and physical processing (Angier, 2002). The in-stream processing was described using the measured stream length that flows through palustrine wetlands upstream of each point where in-stream chemistry was measured. The stream lengths (in meters) were then multiplied by a processing rates (mg/s/m) which then results in a 1-D in-stream nutrient processing model to account for the observed negative differential solute fluxes between downstream observation locations. Optimizations for the final nutrient concentrations included a calibrated value for the Mason Waste Water Treatment Plant (MWTP). Using a direct mass flux was used to help improve the optimizations because a large bias within data existed due to large values of nutrient mass flux downstream of Jefferson. The location of the MWTP is between Jefferson and Harper observation sites, which explain the large increase for both TP and nitrate. 108 RESULTS AND DISCUSSION Optimization Results The optimization of simulated fluxes from MT3D along with in-stream processing rates, helped explain the negative fluxes observed in the field nutrient data. Along with optimizing input concentrations for land cover, in-stream processing rates were also optimized for nitrate and TDP. Adding the in-stream processing rate to the TDP optimization did not improve matches between simulated and observed TP fluxes. However, optimizing the in-stream processing rate significantly improved the matches between simulated and observed nitrate fluxes. Using values for TP and Nitrate inputs from the MWTP improved the optimization results. After numerous optimizations of nitrate and TDP simulated fluxes while just using in-stream processing, nutrient loading from the MWTP was added for both nutrients. Nutrient flux, for both nitrate and TDP, was first estimated for MWTP. After additional optimizations of input concentrations, instream processing rates, and nutrient loading rates from the MWTP for both nitrate and TDP, the summed error between the simulated fluxes and observed fluxes was reduced significantly (Figure 3.9). From the optimizations it is estimated that the MWTP inputs a total flux of 1950 mg/s for nitrate and a total flux of 98 mg/s for TP on average. During the optimizations of nitrate and TDP simulated fluxes, four optimization scenarios were run using 1) Observed and Simulated Total 109 Concentration; 2) Observed and Simulated Differential Concentration; 3) Observed and Simulated Total Flux; and 4) Observed and Simulated Differential Flux. Overall, the optimizations of differential and total nutrient flux provided smaller summed error than using either total or differential nutrient concentrations. Thus, only results from differential and total nutrient flux are presented in Figure 3.9. Optimization of total nutrient flux had better R-squared and thus the optimized input concentrations, using total nutrient flux, are used in the final transport model. Final MT3D Model Results Simulations of Nitrate and TDP provided a quantitative ability to assess loadings from each land use type for Sycamore and Mud Creeks. Using the final concentrations from the optimizations with the simulated groundwater fluxes, mass flux from each land use in Sycamore and Mud Creeks were calculated for each nutrient. Mass fluxes from groundwater were calculated by entering the optimized concentrations into MT3D and running the transport model to simulate the final in-stream concentrations and mass fluxes for Sycamore and Mud Creeks. These simulations indicate that urban areas are likely the primary source for TP loading while Rangeland is the main source of nitrate into Sycamore and Mud Creeks (Figures 3.10 to 3.14). Agriculture appears to be the secondary source of loading for nitrate and TP in the SCW, however, there is significant uncertainty associated with this flux as agriculture was insensitive in the optimizations. 110 Simulated NOx (mg/s) Nitrate Total Flux 2500 2000 1500 1000 y = 1.0099x 500 R = 0.8711 2 0 A 0 500 1000 1500 Observed NOx (mg/s) 2000 Simulated NOx (mg/s) Nitrate Differential Flux B 2000 1500 1000 y = 1.0132x 2 R = 0.8485 500 0 -500 -500 0 500 1000 1500 2000 Observed NOx (mg/s) Figure 3.9: Optimization results for Simulated and Observed total and differential fluxes for Nitrate (A, B) and TDP (C, D) with in-stream processing coefficients. 111 Simulated TDP (mg/s) TDP Total Flux 120 100 y = 1.0828x 2 R = 0.4512 80 60 40 20 0 0 C 20 40 60 80 Observed TP (mg/s) TP Differential Flux Simulated TDP (mg/s) 120 100 80 60 40 20 0 -20 -40 D y = 1.0796x 2 R = 0.2472 -20 -10 0 10 20 Observed TP (mg/s) Figure 3.9 Continued 112 30 40 Figure 3.10: Simulations based on the final optimized nutrient concentrations from Agriculture, Pasture, Septic Tanks, and urban areas. 113 Sycamore Creek 80 60 50 40 30 20 Total Flux (mg/s) 70 10 0.6 3.3 11.7 17.2 26.3 29.2 0 33.2 Distance downstream (km) Urban Agriculture Pasture Septic Observed Total Flux Mud Creek 12 8 6 4 Total Flux (mg/s) 10 2 0.8 6.3 10.2 14.5 0 19.9 Distance downstream (km) Figure 3.11: Simulated and Observed TDP Flux from different land cover for Sycamore and Mud Creeks. 114 0.6 3.3 11.7 17.2 26.3 29.2 2000 1800 1600 1400 1200 1000 800 600 400 200 0 33.2 Total Flux (mg/s) Sycamore Creek Distance downstream (km) Urban Agriculture Pasture Septic Observed Total Flux Mud Creek 600 500 400 300 200 Total Flux (mg/s) 700 100 0.8 6.3 10.2 14.5 0 19.9 Distance downstream (km) Figure 3.12: Simulated and Observed Nitrate Flux from different land cover for Sycamore and Mud Creeks. 115 0.6 3.3 11.7 17.2 26.3 29.2 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 33.2 Concentration (mg/L) Sycamore Creek Distance downstream (km) Agriculture Pasture Septic Observed Concentration Mud Creek 0.06 0.05 0.04 0.03 0.02 0.01 0.8 6.3 10.2 14.5 Concentration (mg/L) Urban 0 19.9 Distance downstream (km) Figure 3.13: Simulated and Observed TDP Concentration from different land covers for Sycamore and Mud Creeks. 116 Sycamore Creek 4 3 2.5 2 1.5 1 0.5 0.6 3.3 11.7 17.2 26.3 29.2 Concentration (mg/L) 3.5 0 33.2 Distance downstream (km) Urban Agriculture Pasture Observed Concentration Septic Mud Creek 2.5 2 1.5 1 0.5 0.8 6.3 10.2 14.5 Concentration (mg/L) 3 0 19.9 Distance downstream (km) Figure 3.14: Simulated and Observed Nitrate Concentrations from different land cover for Sycamore and Mud Creeks. 117 CONCLUSIONS The results from this approach show that both nitrate and TDP fluxes can be reasonably simulated using a simple method with linear superposition of inputs from different land use types and septic inputs, with an added linear processing term in wetlands along the streams. Simulated fluxes from MT3D compared reasonably with in-stream nutrient measurements at low base flow. The optimized total nitrate fluxes suggest that pasture accounts for a large percent of the nitrate loading into streams at low base flow. It also appears that TDP from urban areas are significant sources of TP at low base flow. Unit concentrations, 1 unit concentration (mg) per unit volume (L) or 1 mg/L, assigned in MT3D, combined with the superposition (summed simulated concentrations) of all the land covers, enabled a simple optimization model that can be applied to other eco-hydrology studies. Optimization of NOx and TDP differential and total fluxes provided valuable insight on how multiple land covers can impact nutrient loading to streams via groundwater transport. Describing the in-stream processing with only stream length flowing through wetlands helped explain negative differential fluxes observed within the measured in-stream nutrient data for nitrate. 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