A Dynamic, Distributed Hydrologic Model for the Blue Earth River Watershed, Minnesota With Implications Regarding Land Use and Water Quality

Abstract

The Blue Earth River (BER) watershed covers approximately one million acres of south-central Minnesota and northern Iowa. Modern farming practices have led to the loss of over 90 percent of the watershed\u27s original wetlands. Corresponding changes in runoff and stream flow have led to dramatically reduced water quality in the BER\u27s main stem following most precipitation events. The purpose of this research is to examine the relationships among precipitation, infiltration, base flow, and runoff in the Blue Earth River watershed basin. This study developed a calibrated numerical hydrologic model for BER watershed using the distributed flow model, Vflo™. The model was developed the seven major runoff events for the 2008 monitoring season (March – June). The research showed the importance of soil depth, hydrologic conductivity, and initial saturation in simulating peak flow volume. Where as overland roughness and channel roughness were found to attenuate the timing of the peak flow volume within the channel. The calibrated model is able to simulate flows where flows have not been observed in the field in both temporal v and spatial dimensions. The model is able to accurately depict the onset of the rising limb event and peak discharges to within ten percent of each event. Results of this research provide a better understanding of the hydrologic regime, prediction of flow rate, depth, and flow-weight total contaminant loads, of the BER watershed. These results therefore provide an objective means for improving best management practices within the Blue Earth River watershed