IMPACTS OF LAND USE/LAND COVER CHANGE ON STREAM FLOW (THE CASE OF MEKI RIVER, RIFT VALLEY BASIN, ETHIOPIA)

Abstract

Land use land cover change has an impact on the alteration of watershed streamflow. In the last 24 years,Meki catchment experienced significant land use land cover change, which is the major contributor of runoff for Lake Ziway. This study quantified basin runoff volume using the SWAT model and assessed the effect of land use land cover change on the streamflow. Geographic Information system (GIS) was integrated with the SWAT model to carry out the study. Arc GIS10.3 and ERDAS IMAGINE2014 were used to process soil raster data set and prepare land use land cover map from Land sat image acquired in 1996, 2006, and 2020 respectively and gives the following classes of land(agricultural land, built-up area, wetland, shrubland, forest, grazing land, water body and bare land). Land use classification was performed using a supervised classification system and accuracy assessment was done using a confusion matrix. The classification result indicated the expansion of agricultural land, built-up area, and water bodies. Using the three-land use land cover maps, the SWAT model was set up and run. Sensitivity analysis was made on a monthly basis using 10 model parameters where only eight parameters were identified that influence the flow. The model calibration was done from 2000 to 2008 and the validation period from 2009 to 2012.The calibration and validation results showed a good match of simulation with observation with Nash-Sutcliff efficiency 0.75and 0.69coefficient of determination (R2 ) 0.81 and 0.78 for calibration and validation respectively. The calibration and validation results showed a good match of simulation. The result showed that the mean wet monthly flow increased by 19.21% (from 26.79m3/s for lulc of 1996 to 37.73m3/s for lulc of 2020) and the mean dry monthly flow decreased by 48.69% (from 15.81m3/s for lulc of 1996 to 12.76m3/s for lulc of 2020). Generally, the study result indicated that the flow during the wet season increased whereas during the dry season decreased. The study results showed a change in flow with a change in land use/cover. It was concluded that the streamflow of the Meki river increase in a seasonal scale as a result of land use land cover changes