IMPACT OF LAND USE/LAND COVER CHANGE ON CATCHEMENT HYDROLOGY: THE CASE OF GIDABO CATCHEMENT, RIFT VALLEY LAKES BASIN, ETHIOPIA

Abstract

The study analyzed the land use/land cover change between the 1996, and 2016, and the effect these changes had on Hydrology on Gidabo catchment. Within Gidabo catchment land use is undergoing major changes due to pressures of human activities. Changes in land use have potentially large impacts on water resources by causing more surface runoff, decreased water retention capacity, loss of wetland and drying of river. In this study, both the Soil and Water Assessment Tool (SWAT) model and Spearman`s rank correlation statistical time series analysis for measured stream flow were applied to understand the stream flow variability and land use dynamics effect on stream flow of Gidabo catchment. Land use maps of 1996, 2006 and 2016 were derived from satellite images and analyzed using ERDAS Imagine 2014 software. From the land cover change analysis results it was found that there has been a substantial decline of forest lands, shrub lands, wet lands and drastic expansion of agricultural land. The SWAT modeling results showed that an increase of stream flow by 21% comparing the three land use maps (1996, 2006 & 2016). The analysis also revealed that flow during the wet months has increased by 9.53 % while the flow during the dry season decreased by 2.36 %. Generally, the combined results of the SWAT model and the statistical tests revealed that land use change has caused a significant increase on mean annual stream flow and decrease dry season flows of the studied watershed during the period. The identified result is important to inform optimal water resource management and to plan and manage water resources development within the watershed in a sustainable manner