Model Flow Duration and Streamflow Variability

A simple flow duration model is postulated by using data from 120 gaging stations in Illinois. On the basis of model flow duration, a region can be divided into hydrologic divisions. For each division, the coefficient and exponent in the model have distributions with respect to percent time. The variations in the coefficient and exponent are explained in terms of areal and physiographic factors. An objective method is presented for deriving flow duration of an ungaged stream in a hydrologic division by using model flow duration.