A mathematical model of hillslope and watershed discharge

A mathematical water balance model describing major hydrological processes operating within wet forested watersheds is proposed. The model is capable of predicting hillslope and watershed discharge, evapotranspiration demands, hillslope moisture status, and surface and subsurface flow rates. It is based on soil physical principles and requires the following input variables: average hillslope angle and width, average soil depth, precipitation, average daily evaporation rates, effective saturated hydraulic conductivity, soil moisture holding capacity and initial moisture content. These variables are often easily measured from field studies. However, in some cases, the absence of field data may require that some of the variables in the model, e.g., saturated hydraulic conductivity, be estimated or calibrated from hillslope hydrograph records. The watershed model is composed of two submodels: a storage model and a hillslope model. The storage model describes the dynamic variation in water table elevation in recharge zones and the hillslope model is used to predict runoff and seepage through flow from surrounding hillsides. Application of the model is illustrated on a small watershed located in North Madison, Connecticut.