Design and Implementation of Optimized Hydrologic Unit Watersheds for Rainfall-Runoff Modeling

The construction of rainfall-runoff models represents one of the most complex and challenging problems in water resources engineering. This is particularly true for urban watersheds in which, the entire watershed is discretized in smaller sub-basins and additional systems need to be modeled such as the drainage network. This work was aimed at developing a methodology for the development of a rainfall-runoff model that characterizes a complete drainage area using SWMM5. ArcHydro was used to sub-divide the entire basin in sub-watersheds; then, a kinematic wave cascading plane approach was used to convert irregular sub-watersheds to regular shapes. The so-called Hydrologic Unit Watershed (HUW) represents a synthetic sub-watershed, in which their hydrologic parameters are chosen by constrained optimization. Rather than using individual storms for calibration, the goal was to minimize the difference between the flow duration curves of the model output and observed discharges.