Evaluation of Depression Storage Using Grid-Based GIS Model

Depression Storage is a volume that must be filled former to runoff. It might be treated as a rectification parameter to adjust runoff volumes and peak discharges. A semi-distributed GIS model is constructed for watershed delineation on a pixel scale. Model simulates hydrological processes of precipitation, surface runoff and depression storage, where water balance is maintained for each pixel. The total Surface runoff is produced using (SCS CN) method that accounts for land use, soil cover and soil type. Total precipitation is calculated based on a uniformly distributed storm over the study area. The model attempts to calculate the depression volume within the study area by using the Arc Hydro toolbox as well as the Spatial Analyst in the ArcGIS platform. Model purpose is to develop a more accurate estimation of initial ions due to the presence of depressions over the duration of the adopted storm event. The goal is to evaluate the effect of depressions on total surface runoff volumes and peak discharges using the model which could significantly reduce the sizing of the hydraulic structures.