Hydrologic variations owing to snowmelt changes in the mid latitudes

Snowmelt is a critical hydrologic process in high latitude, non-alpine settings. The water stored in seasonal snowpacks melts in the spring months leading to increased spring streamflow and creating shallow groundwater recharge that helps sustain streams throughout the year from the contributions of baseflow. Many regions across the globe have experienced changes to snowpack dynamics and melt patterns due to increased winter temperatures resulting from global climate change. Currently, most of the research into the changing snowmelt hydrology has been focused on mountainous regions where snowpacks make up larger portions of those regions' annual water budget. There is little research in these mid-latitude, non-alpine areas and the available research focuses on small areas or examines only one component of the hydrologic system.These understudied regions that receive seasonal snowfall require more thorough examination as changes to winter and spring snow can have negative societal consequences, especially in one of the world's largest freshwater reservoirs of the Great Lakes.This dissertation contributes to the scientific knowledgebase regarding snowmelt dynamics in non-alpine settings. Novel statistical analyses are utilized to assess the amount of change to winter temperatures and the effects on snowmelt hydrology across spatial scales and decades of observational data. The results from these analyses are then used as a lens to simulate the landscape hydrology to quantify changes to shallow groundwater recharge, which is difficult to assess from empirical data alone. These findings also lead to an examination of the potential economic effects resulting from changes to the snowpack.Chapter 1 lays the groundwork for this dissertation by describing the relevance of the research and gives a brief overview of the different components. The foundational methodology is developed in Chapter 2, where a combination of observed physical data and outputs from several snow and precipitation models are used to classify winters in Michigan from 2003-2017 as warm or cool and quantify the hydrologic changes in those different winter types. The results show warmer winters had less overall snow, which melted earlier contributing to earlier and lower spring stream flows and increased net recharge of groundwater. Chapter 3 then takes this methodology and applies it to the entire eastern portion of the United States that receives seasonal snow from 1960-2019, with results similar to the preceding chapter, and demonstrating that these snow hydrology changes are not limited to Michigan or to the more recent decades. These findings then culminate in Chapter 4, where the Landscape Hydrology Model simulates the snowpack, surface flows and groundwater recharge in Michigan from 2000-2019. These fully distributed simulations show the decreased snow and periodic melting in warm winters has led to increased groundwater recharge and decreased surface flows. Chapter 5 concludes this dissertation by examining the downhill ski industry in Michigan using industry statistics and operational data from the Shanty Creek Resorts, describing the potential economic challenges in a warming future.