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 principal input parameters which define hydrologic respon se units on a watershed was evaluated. The study was conducted on a small a gricultural watershed in Ohio. The results suggest that useful estimates of monthly flows could be obtained by using NRCS soils information, land use, and tillage information estimated from Landsat TM data, a 30-meter digital elevation model, and readily available information on the prevailing farmi ng systems. Water quality and quantity responses were sensitive to combinat ions of the slope, soil type, land use, tillage, crop rotations, and draina ge practice and should be taken into account in defining the hydrologic res ponse units. The sediment load predictions were sensitive to the field size . Approximations of when planting occurred did not affect the flow and sedi ment predictions but had an impact on nitrate and pesticide predictions.