COUPLED MODELING OF GROUNDWATER AND SURFACE WATER IN AN AGRICULTURAL WATERSHED TO GUIDE WATER RESOURCE MANAGEMENT

Managing groundwater resources has become significantly more challenging given the need to balance an increasing trend in appropriations while properly accounting for groundwater-surface water interactions and the associated effects on water quality, biology, and recreational use. In many agricultural regions changes in land use and increases in irrigation pumping are impacting surface waters through reduction in baseflow, increased temperatures, and loading of nutrients. New methods have been developed that couple models of surface hydrology with groundwater models, allowing managers to make decisions on how best to protect both surface water and groundwater in a holistic manner. We present an example from the Little Rock Creek watershed (a protected trout stream) in Minnesota that applied coupled models to evaluate the combined effects of land use and groundwater pumping changes on surface water quality. This project resulted in Total Maximum Daily Loads (TMDLs) for dissolved oxygen, nitrate, and temperature. Strategies to meet these TMDL’s involve both surface water and groundwater management.