Hydrologic and Sediment Transport Modeling of Agricultural Watersheds

Abstract

Dealing with flooding, upland soil and streambank erosion, sedimentation, and contamination of water from agricultural, rural, and urban watersheds, and understanding the underlying natural processes are continued challenges to the environmental hydraulics field and in the management of sustainable water and environmental resources around the world. Watershed simulation models are useful tools to understand and analyze the processes and the problems and help mitigate those through evaluating the effects of land-use changes and best management practices. Developing adequate watershed simulation models and verifying those on real world watersheds with measured and monitored data are challenging. A Dynamic Watershed Simulation Model (DWSM) is being developed at the Illinois State Water Survey to simulate surface and subsurface storm water runoff, propagation of flood waves, soil erosion, and transport of sediment and agricultural chemicals in agricultural and rural watersheds. Different components of the DWSM have been applied to watersheds in Illinois for testing these components and assisting local watershed planning groups in planning restoration projects. Some of the recent progresses made in this ongoing modeling study are presented here. The soil erosion and sediment transport component was tested (calibrated and verified) on the Big Ditch watershed in Illinois, a 100-square-kilometer tributary subwatershed of the Upper Sangamon River basin draining into Lake Decatur. Two different divisions of the watershed, one with coarse subdivisions and the other with fine subdivisions were used in the simulations to investigate scaling effects on the parameter values and the model results.