Abstract

The knowledge of runoff discharged by a catchment at its outlet is important for water accounting and water allocation to competing uses. Runoff generated by a catchment is important in determining the catchment water balance, estimating pollutant loads, and quantifying sediment yield and delivery ratio. The Soil Conservation Service triangular unit hydrograph (SCS-TUH) model was used in this study to simulate water discharged into Siya Dam from Rosva River Catchment in Masvingo Province, Zimbabwe. The SCS-TUH model is preferred because it takes into consideration the physical and hydrological conditions of a catchment, as well, as the volume and flow variations of the entire rainfall event. The model simulates the peak runoff rate of a catchment using daily rainfall data. An overview of the methodology and the different steps followed are given. The model results were validated by comparing the simulated values with measured values recorded from a gauging station at the catchment outlet. The plotted hydrographs of both simulated and measured values coincided very well in height as well as in shape with great precision. The results showed that the SCS-TUH model can be used for simulating runoff discharge in ungauged catchments in the region.

Key words: Peak runoff rate, water availability, water allocation, water management, water balance.