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Kesem watershed, land use/cover change, stream flow, SWAT, trend analysis


The main objective of this study was to investigate the impacts of land use/Land cover change impacts on streamflow availability in The Kesem Watershed, Awash basin, Ethiopia. Two methodological approaches were employed to achive the objective. The Soil and Water Assessment Tool (SWAT) model was used to quantify the changes using two time period land use maps. Moreover, Mann-Kendall (MK) statistical test was used to detect the monotonic trends if exists in the time series of the measured and simulated streamflow. Land use change detection was done using remote sensing techniques and the maps were processed using ERDAS Imagine 2014 and ArcGIS10.1 software. From the land cover change analysis results it was found that there has been a substantial decline of forest lands, shrub lands, grass lands and drastic expansion of agricultural land.

The SWAT modeling results showed that an increase of streamflow by 23.2% comparing the two land use maps (1993 versus 2005). The analysis also revealed that flow during the wet months has increased by 36.4% while the flow during the dry season decreased by 33.6%. The investigation of the streamflow trends on the mean annual, seasonal, 1- and 7-days annual minimum and maximum flows depict that in the case of 1-day maximum flow, no significant trend is noticeable; however, the extreme low flows indicators (e.g. 1D minimum, 7D minimum) and dry seasonal flows exhibited statistically significant decreasing trends (p =0.015, 0.0016 and 0.005) respectively. Overall, the combined results of the SWAT model and the statistical tests revealed that land use change has caused a significant increase on mean annual streamflow and decreasing dry season flows of the studied watershed during the last three decades. The identified result is important to manage the water resources in an optimal manner. Besides, planning of water resources development in the basin, should take into account land use change scenarios in order to bring sustainable development in the basin.