The Sensitivity of Adapt Model Predictions of Streamflows to Parameters Used to Define Hydrologic Response Units

The responses of ADAPT, a daily water table management simulation model, to variations in the principalinput parameters which define hydrologic response units on a watershed was evaluated. The study was conducted on asmall agricultural watershed in Ohio. The results suggest that useful estimates of monthly flows could be obtained byusing NRCS soils information, land use, and tillage information estimated from Landsat TM data, a 30-meter digitalelevation model, and readily available information on the prevailing farming systems. Water quality and quantityresponses were sensitive to combinations of the slope, soil type, land use, tillage, crop rotations, and drainage practiceand should be taken into account in defining the hydrologic response units. The sediment load predictions were sensitiveto the field size. Approximations of when planting occurred did not affect the flow and sediment predictions but had animpact on nitrate and pesticide predictions.