Using SWAT model to evaluate the impact of community-based soil and water conservation interventions for an Ethiopian watershed
Addis, Hailu Kendie
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Extensive land degradation in the Ethiopian highlands forces the rural communities to prevent further soil erosion to ensure sustainable land management in the endangered regions. Soil conservation measures are continuously being established in some areas by research and/or development projects but the effects at field and watershed level are unclear. The objective of this study is to model runoff and sediment yield in the Gumara-Maksegnit watershed in the northern Amhara region, to assess the impact of selected soil and water conservation interventions. SWAT was used to simulate the 54 km² large watershed, locally treated by stone bunds and water retention ponds, based on SRTM-DEM data, soil data derived from 234 observations, a land-use map based on supervised satellite-image classification and weather data from four different rain gauges. Runoff and sediment concentration was monitored at three gauging stations to provide a reliable model calibration. Comprehensive field monitoring was undertaken to assess upland and channel processes and thus to consolidate the model performance. By means of the calibrated model mean annual runoff (271 mm) and soil loss (22.6 t ha-1) was calculated and the highly endangered regions concerning land degradation were located. The achieved NSE of modeled and observed daily runoff of 0.777 indicates that the SWAT model can be properly used for the assessment of the on-site watershed characteristics and based on this, various scenarios can be simulated to identify efficient soil conservation strategies for the study area.