Water scarcity has become a serious global problem. Therefore, there is an urgent need to understand land use changes in watershed areas and their impact on river flows. This study models the impact of land use changes on river flows in the Arror watershed in Elgeyo Marakwet County, Kenya. The primary study sources included remotely sensed and socio-economic data. Landsat 5 thematic mappers for 1986, 2000 and 2012 (resolution 30 m) were used. A 90 m Digital Elevation Model resolution was used to delineate the Arror watershed. Secondary data included climate, river discharge and soil data. Field surveys and questionnaires were used to collect socio-economic data. GIS was integrated with a Soil and Water Assessment Tool model to determine the impact of land use changes on water quantity. The calibration goodness of fit results for the model were 0.9 and 0.8, for EF (Nash-Sutcliffe Efficiency) and R-squared, respectively. The results show a reduction of 3.5% of deciduous forest and 11.8% of grassland, while agricultural land increased by 14.3% from 1986 to 2012. The 1986, 2000 and 2012 land uses yielded an annual average flow of 2.0, 2.5 and 1.9 m3/s respectively. Flow variation was attributed mainly to land use changes. Agroforestry and afforestation are recommended for sustainable watershed management.

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