Assessment of Rainfall-runoff Relation/mechanisms Under Different Land Uses and Landscape Position in North Western Ethiopia

Purpose: This research aimed to develop rainfall-runoff relations for different land use types, to establish a relationship between runoff and soil loss under different land use and soil moisture conditions, and to evaluate the variation of soil water content in different depths of soil and land use types. Methods: An automatic and manual rain gauge that was installed in the watershed at the nearby testing plots was used to record the rainfall data. Three separate plots with various land uses and slope positions were used to gather runoff and sediment loss. Every morning -at 6:30 a.m., runoff and sediment data were collected from the runoff plots following each rainstorm occurrence. Result: The rainfall-runoff relations on all land use types were significant at (P<0.001). The infiltration rate and rainfall intensity analysis show that the dominant runoff generation mechanism of the watershed was saturation excess. The ECH2O Ec-5 soil moisture sensor probes show that the volumetric soil moisture content increased with increasing soil depth on grazing land, while the reverse happened on the cultivated land. The volumetric moisture content on both land use types had very high statistical significance among the 5 depths of the soil (P<0.001). Conclusion: Steep slope areas should be closed and there should be some afforestation program in the area. Free grazing grasslands should be changed to closed grazing land use systems.