Understanding rainfall runoff dynamics across various land uses and landscape positions in North Western Ethiopia

The hydrological cycle and soil dynamics in watersheds are significantly influenced by land use and topographical variations. This study explores the rainfall-runoff dynamics across various land uses and landscape positions in the Abagerima watershed, North-Western Ethiopia. In the watershed land degradation, soil erosion, and runoff are critical environmental challenges. The primary objectives were to develop rainfall-runoff relationships for different land use types, establish connections between runoff and soil loss under varying land uses and soil moisture conditions, and evaluate soil water content variations at different depths and land use types. Rainfall data were collected using both automatic and manual rain gauges installed within the watershed. Runoff and sediment loss data were gathered from three distinct plots with different land uses and slope positions, recorded daily at 6:30 a.m. following rainstorm events. The analysis revealed significant rainfall-runoff relationships for all land use types (P < 0.001). The watershed's dominant runoff generation mechanism was identified as saturation excess, based on infiltration rate and rainfall intensity data. Soil moisture measurements were conducted using ECH₂O Ec-5 soil moisture sensor probes which indicated that volumetric soil moisture content increased with depth on grazing land, while it decreased on cultivated land, with statistically significant differences among the five soil depths (P < 0.001). The findings suggest that steep slope areas should be protected and afforestation programs initiated. Free grazing grasslands should transition to controlled grazing systems to mitigate soil erosion. This research highlights the importance of land use and soil moisture considerations in understanding rainfall-runoff interactions and soil water content variations, providing critical insights for effective watershed management and soil conservation, particularly in regions vulnerable to runoff and erosion.