The Application of the Land Transformation, Groundwater Flow and Solute Transport Models for Michigan’s Grand Traverse Bay Watershed

INTRODUCTION Grand Traverse Bay and the Grand Traverse Bay Watershed (GTBW) are important natural and economic resources for Michigan and the Great Lakes Region, due to their great scenic beauty, quality of waters, and the recreational opportunities these afford. However, the watershed is currently undergoing some of the most rapid population growth and land-use change of any region in the Great Lakes States (Vesterby and Heimlich, 1991). The GTBW Initiative, a not-for-profit organization that works with community groups and university researchers, has identified the following issues of concern in this watershed: erosion and sedimentation, phosphorous and nitrogen inputs to the Bay, degradation of water quality as indicated by algae growth and oxygen depletion in deep waters of the Bay, inputs of toxic substances, and the impact of various land uses and land use protection measures on these (GTBW Initiative Water Quality Monitoring Program Draft, October 16, 1995). Numerous field studies have demonstrated that changes in land use affect groundwater and surface water dynamics. Potential environmental impacts include 1) the redistribution of recharge and discharge areas, and reduced groundwater discharge to streams (Doe et al, 1996); 2) changes in groundwater recharge rates (Thorburn et. al., 1991); and 3) changes in stream flow and temperature with subsequent influences on stream ecology (Wiley et al. 1997). Likewise, land use/cover patterns and changes in land use/cover have been found to influence surface water chemistry. Effects have also been shown on the chemistry of major ions (Cl) and nutrients Variations in land use change affect surface and groundwater hydrodynamics by varying the amounts of impervious or erodable surfaces and by redirecting water flow paths. Such parameters are often incorporated into models that examine the input of non-point source (NPS) pollutants to surface waters (e. groundwater leaching of NPS contaminants – reviewed by Corwin and Wagenet, 1996). These studies underscore the need to quantify the effects of land use on ground water quality and hydrologic dynamics. Spatial-temporal models coupled to geographic information systems (GIS) can be powerful tools to quantify these relationships. This paper presents the application of one land and two hydrologic models to understand the coupling of land use and water quality in Michigan's Grand Traverse Bay Watershed. The Land Transformation Model (Pijanowski et al., 1996, Pijanowski et al., 2000a, Pijanowski et al., 2000b) couples Artificial Neural Network (ANN) routines to GIS databases containing information on population growth, transportation factors, and locations of important …