Uncertainty in Sediment Yield from a Semi-Arid Watershed

Abstract

The paper presents a stochastic model for the prediction of sediment yield in a semi -arid watershed based on rainfall data and watershed characteristics. Uncertainty stems from each of the random variables used in the model, namely, rainfall amount, storm duration, runoff, and peak flow. Soil Conservation Service formulas are used to compute the runoff and peak flow components of the Universal Soil Loss Equation. A transformation of random variables is used to obtain the distribution function of sediment yield from the joint distribution of rainfall amount and storm duration. The model has applications in the planning of reservoirs and dams where the effective lifetime of the facility may be evaluated in terms of storage capacity as well as the effects of land management on the watershed. Experimental data from the Atterbury watershed is used to calibrate the model and to evaluate uncertainties associated with our uncertain knowledge of the parameters of the joint distribution of rainfall and storm duration.