Impact of land use and landscape on runoff and sediment in the sub-humid Ethiopian highlands: The ene-chilala watershed

Abstract

The effect of land cover and landscape on runoff and sediment yield was evaluated in the Ethiopian highlands. We selected three small catchments: agriculture dominated watershed, bush & agriculture dominated watershed and agriculture dominated but with higher coverage of bush & grass watershed compared to the other two watersheds with in 399 ha Ene-chilala watershed. Hydrometric, sediment concentration and rill erosion data were measured for two years (2015 and 2016). The result showed that; sediment yield were statistically significant different between watershed one and watershed two. Moreover, the sediment concentration in watershed three varies statistically when compared with watershed one and watershed two. The greater runoff, suspended sediment concentration and yield in the agriculture dominated but with higher coverage of bush & grass catchment (WS3) results from saturated areas and gully erosion in the bottomlands. Since the agricultural land is highly degraded no more soil is transported due to rill erosion (detachment limited) by generated runoff. The bedrocks at the upland of these watersheds generate high runoff. Shallow and deep active gullies at the bottomlands contributed for higher sediment concentration. Our results support that watershed management that involve gully treatment on bottom lands and increase ground cover on degraded agricultural areas to reduce runoff and soil loss.