Modelling the Impacts of Land Use Change on Stream Flow in the Kimwarer Catchment Using SWAT

Abstract

The Kimwarer River basin covers 138.2 km2. It has experienced ecosystem degradation due to extensive farming that has impacted on water yield. This study was undertaken to assess the impacts of land use changes on river flow using SWAT, a mathematical model that has the potential to predict the impact of land management practices on water at catchment scale. Current and historic flow data were collected for model calibration and validation. The model was then used to simulate stream flow for different land use and land cover scenarios by varying the extend of forest cover and agriculture. The model was successfully calibrated and validated for stream flow, and proved capable of predicting flow with R2 and NSE values of 0.79 and 0.31 respectively. During validation, the model predicted flows with R2 and NSE values of 0.70 and 0.50 respectively. For scenario analysis to determine the effect of land use change on stream flow, it was observed that runoff decreased with increase in forest cover, while base-flow increased. Introduction of terraces as a management operation on agricultural land reduced runoff by 46%. It is evident from the study that the current trend of land use change affects stream flow.