MODELLING THE IMPACT OF LANDUSE/LAND COVER CHANGE ON THE STREAM FLOW OF UPPER GUDER RIVER CATCHMENT USING SWAT, ABBAY BASIN, ETHIOPIA

Abstract

Water resources are a critical component of any type of socio-economic development all over the world. Due to extensive agricultural practices, the LU/LC change was the cause of streamflow changes. The main objective of this research was to model the impact of landuse/land cover change on the streamflow of Upper Guder River Catchment using the SWAT model, by using meteorological data in the period between 1989 -2018. Upper Guder River Catchment was one of the catchment of the headwaters in the south Abbay Basin. In this study, the impact of LU/LC change was carried out by using the Soil Water Assessment Tool (SWAT2012) model, which was integrated with GIS10.3 software. GIS and ERDAS IMAGINE2014 were used to generate landuse/land cover maps from Landsat TM, TM, and ETM+ acquired in the years 1989, 2002, and 2018 respectively. The land cover maps were generated using the maximum likelihood algorithm of supervised classification. The classified maps were assessed using confusion metrics. The results of the analysis showed that the Agricultural land has expanded during the study period of 1989-2018. During the study period, forest land, and shrub and grassland decreased by 6.48% and 4.23% respectively while Agricultural land and Built-up area increased by 8.04% and 2.69% respectively. Using three land cover maps, three SWAT model setup were run to evaluate the impacts of landuse/land cover changes on the streamflow of the study catchment. The performance of the SWAT model was evaluated through sensitivity analysis, calibration, and validation by using SWAT-CUP. Statistical measures like coefficients of determination and Nash–Sutcliffe were used to evaluate the model and it resulted in 0.84 and 0.74 for calibration and 0.83 and 0.72 for validation respectively. During the study periods, the simulation result indicated that streamflow increased in the wet season and short rainy season streamflow by 10.04% and 5.25% respectively, while decreasing by 6.60% in the dry season. The Surface Flow (SURQ) increased by 5.73% while Groundwater Flow (GWQ) decreased by 2.26% due to the increment of Agricultural land. The model results showed that the streamflow characteristics changed due to the landuse/land cover changes during the study period. The catchment was sensitive to past LU/LC change, so it needs an effective integrated participatory approach for catchment management.