Subsurface Drainage and Sediment Transport Model

ABSTRACT A computer model was developed, using the GASP IV simulation language to simulate the water flow and sediment movement from a subsurface drainage system. The model used a one dimensional form of the Richard's equation and a steady state tile flow formula by Toksoz and Kirtham (1961) to express the water movement pro-cess. The particle detachment portion of the model, which was based on a force balance relationship, was controlled directly by the output of the flow portion of the model. Data required by the model included rainfall, evapotranspiration, soil properties, and the drainage system layout. Calibration and verification were completed using data collected from a seventeen hectare tile drainage system located on a tlat Hoytville silty clay soil. A com-parison of simulated and observed results indicate that the model will reliably predict water yield, sediment yield and the sediment concentration curve. However, some difficulty in simulating the actual shape of the flow hydrograph occurred.