Prairie fens provide habitat to more than 50 rare species, including the federally endangered Mitchell's satyr butterfly. Substantial resources have been invested in their protection; however, these conservation efforts have proceeded without an understanding of the underlying groundwater flow regime that is critical to these fens. Regional scale hydrological investigations could cost hundreds of thousands of dollars for an individual fen, and are therefore rarely undertaken in a management context - confining the conservation efforts to the local fen community and adjacent lands. Without delineation of groundwater sources, the conservation community has had limited ability to protect the fen groundwater quantity and quality. In this research we explored the use of an informatics-based, data driven modeling approach for groundwater modeling and to improve our ability to understand fen hydrology at different spatial scales. The approach used in this study directly analyzes, filters, and processes water well records and surface water elevations to estimate groundwater flow. We developed a steady state mean flow model for the southern Michigan basin, regional scale models for 9 fen clusters/sites, and site-specific vertical profile models for 19 selected fens. Vertical profile models facilitated understanding groundwater delivery mechanisms from regional recharge mounds to individual fens. Our major findings from these models are: 1) on a regional scale, occurrences of fens exhibit a clear systematic pattern; 2) most prairie fens are located around or at the foot of several large groundwater "mounds" at the intersection of major watersheds. These mounds are critical, regional source water areas for aquifer systems, fens, and other groundwater-dependent ecosystems (GDE); 3) these critical regional mounds play a disproportionally large role controlling the sustainability of groundwater resources and GDE; 4) Groundwater flow patterns in the regional source water areas are complex and most fens are recharged from multiple sources; 5) Prairie fens located seemingly far apart in different watersheds, counties, or even different states may share the same regional source water; and, 6) The models revealed four distinct mechanisms of groundwater upwelling into the fens: i) shallow connection - groundwater recharge from local hills and surface water in lakes/wetlands at higher elevations adjacent to a fen seeping into the fen through shallow and relatively short groundwater flow paths; ii) deep connection -source water recharge at distant locations coming in contact with deeper glacial/bedrock formations before upwelling into the fen; iii) confined connection -a distant source water recharge area becomes connected to a fen through older outwash beds confined under recent till plains; and, iv) cascading connections -groundwater sources directly linked to fens being dependent on other surface/sub-surface source waters.These findings have significant practical implications and support the need to reconsider the current priorities and restoration strategies. In particular: 1) our improved ability to use GIS data creates new possibilities with basin-wide implications for the holistic management of fen ecosystems; 2) fen management must move beyond water's edge to account for the impact of regional flow systems; 3) because of the connectivity of the basin's groundwater systems, a few "smart" actions in key locations could yield high ecological returns; 4) when we protect prairie fens and their upstream sources, we are also protecting other ecosystems downstream; and, 5) occurrence of fens in the regional aquifer recharge areas at the intersections of watershed boundaries implies that coordination across the river basins as well as the political divides and between water resources and ecological communities would be imperative for protection of fens.
Read
