QUANTIFYING THE IMPACT OF LAND USE AND CLIMATE CHANGE ON
GROUNDWATER/SURFACE WATER INTERACTIONS IN REGIONAL GREAT LAKES WATERSHEDS

Principal Investigators: David W. Hyndman, Bryan C. Pijanowski, and Phanikumar S. Mantha

Changes in land use, such as urbanization and deforestation, are likely to adversely affect water cycle dynamics (IJC 1997, USGCRP 2001). Land use directly influences evapotranspiration and overland flow, which in turn affect the spatial and temporal distribution of groundwater and surface water interactions (Lu et al., 1998). In the Upper Great Lakes region, several large-scale land use changes have occurred over the last 150 years that have impacted water cycle fluxes. In the late 1800s, most of the old growth forests in Michigan and Wisconsin were logged to provide building materials for the region‘s large cities, most notably Chicago and Detroit. Much of this land was converted to agriculture in the early 1900s with another expansion in the 1960s that caused significant wetland and forest loss. In the last 30 years, urban sprawl has caused conversion of many marginal agricultural lands into residential and commercial uses.

Climate change also significantly alters hydrologic dynamics. Noticeable changes over the last two decades include declines in lake levels to historical lows, reduced snowpacks and unfrozen lakes due to warm winters, and increased incidence of droughts and floods (EPA 1995). Climate change models predict that the Upper Great Lakes region will be 25% wetter and 2 - 4° C warmer by the end of the 21st century, with more large rain events and hot summer periods (USGCRP, 2001). Altering the amount, form, and distribution of precipitation will impact surface water and groundwater fluxes; however the exact nature of these impacts is unknown. The overall objective of our proposed work will be to explore the impacts of climate and land use changes separately, and then synergistically, on the spatial and temporal variation of water fluxes throughout regional Great Lakes watersheds. We will use integrated process based models to quantify the magnitude of these impacts on water distribution throughout one of the world‘s most important freshwater resources. Our approach will incorporate high-resolution measurements of stream flow coupled with historical and future land use estimates to simulate the dynamics of surface water and groundwater fluxes. This will allow us to estimate the spatial distribution of effective recharge to groundwater for measured baseflow conditions, which will then be used to evaluate temporal changes across two well studied experimental watersheds that drain into the Great Lakes. Our existing models of the well instrumented Muskegon River and Grand Traverse Bay Watersheds in Michigan will be redeveloped within a finite element framework to predict the spatial and temporal variability in water cycle fluxes. We believe that our proposed work has high intellectual merit because few studies have: (1) adequately addressed the interaction of climate and land use on water dynamics, (2) fully integrated three-dimensional groundwater and surface water flow models, (3) applied high-resolution stream flow data in a process model framework to estimate recharge rates for different land covers; and, (4) developed process based land-climate-hydrology models at the experimental watershed scale.

Broader Impacts

Our work will also have significant broader impacts. First, the results of our analysis and modeling will help explain complex relationships between climate, land use and the water cycle at —scales that matter“. Second, we will examine likely future scenarios of land use and climate change in order to generate information that can be used by local, state, regional and federal agencies in decision making. Third, our education activities will provide students with a broad understanding of these important climate-land-water interactions as well as provide them with critical thinking skills through a multidisciplinary environment. Finally, we will engage community stakeholders within our experimental watersheds, to provide them with information on how their actions affect water cycle dynamics in their region.

Copyright by Purdue University 2007

Last updated by BCP on March 4, 2007