Application of Ihacres Conceptual Rainfall-Runoff Model to Simulate Daily Stream Flow in Upper Tana Basin, Kenya

Abstract

Stream-flow measurements are important for water resources assessment and management. In Kenya, inadequate streamflow data poses a major challenge to water resources assessment and management. Application of rainfall-runoff models to the catchments can be used to generate streamflow data. A lumped conceptual rainfall-runoff model IHACRES was applied to six medium sized catchments in the Upper Tana River Basin of Kenya. The model IHACRES was chosen because it requires only catchment area, streamflow data and a surrogate variable representing evaporation such as temperature. In addition, it has only two parameters to be varied during calibration. Streamflow data for the six catchments spanning six years was used in the present study. Simulated streamflow was compared with the observed streamflow for these catchments and the goodness of fit evaluated. The calibration R2 ranged from 0.57 to 0.85 while the simulation R2 ranged from 0.55 to 0.77 for all catchments. The Nash-Sutcliffe (1970) efficiency ranged from 0.78 to 0.91 for calibration and from 0.77 to 0.88 for simulation. Sensitivity tests were also carried out using results for one of the catchments. IHACRES is capable of simulating daily streamflow given concurrent daily rainfall and temperature data and offers a possibility of infilling missing data or generating a long series of streamflow data for water resources management in the Upper Tana River basin