Abstract
Soil and water assessment Tool is used to model the hydrology of a mountainous catchment in tropical Africa. Land cover and soil characteristics for the catchment were used to determine initial model parameters that were later adjusted during a calibration process. The model was calibrated and validated against measured stream flow. Although the model performed satisfactorily for simulating monthly river flows based on SWAT model calibration guidelines, it fell short of capturing daily peak flows. Average error on prediction of daily peak flows was -19.8%, while the median error was 10.8%.Overall, the average simulated daily peak flow was 2.6cms less than the corresponding observed daily peak flow, indicating a model tendency to under predict the magnitude of peak events. The inability of the model to capture peak flows was found to be the main limiting factor for its performance.
Highlights
Information on natural condition and form of water resources occurrence is essential for socio economic development
As no two watersheds are alike in their physiographic and climatologically, the results of these studies cannot be extended to other locations because hydrologic responses differ under the same drivers.The present study focuses on the application of Soil and Water Assessment Tool (SWAT) to a relatively small size, mountainous watershed and assesses its effectiveness as a modelling tool in tropical watersheds
Groundwater parameters; threshold depth of water on the shallow aquifer required for return flow to occur (GWQMN), threshold depth of water in the shallow aquifer for returning to the root zone due to moisture deficit or percolation to the deep aquifer (REVAPMN) were ranked high in the sensitivity analysis, changing them did not improve the model efficiency and they remained at the initial values
Summary
Information on natural condition and form of water resources occurrence is essential for socio economic development. Such information is obtained by carrying out a water resources assessment, a process that involves developing a clear understanding of water inflows, storage and outflows and their interrelationship over time. For example benefit to cost ratios for hydrologic data collection of up to 40:1 has been reported [1]. These benefits point to the need for adopting alternative methods that enable water resource assessments to be undertaken for developing countries
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