Impact of Sustainable Land Management Interventions on Soil Moisture Content and Base Flow at Geda Watershed, Central Highlands of Ethiopia

Abstract

Soil erosion by water caused severe land degradation in the highlands of Ethiopia; due to declined soil fertility and water availability both crop and livestock productivity has been negatively affected in the area. To tackle the problem, watershed based sustainable land management interventions have been implemented at Geda watershed since 2012; however, the contribution of the interventions on soil water retention capacities and base flow improvements were not studied. Therefore, this study explored the impact of the interventions on soil moisture content and the dry period base flows by comparing untreated and treated sub watersheds found adjacent each other. Data for soil moisture was collected from crop and grazing plots at 0-20cm and 20-40cm depths during the beginning of the dry season (October) and at mid dry season (January) from both subwatersheds and landscape positions. Discharges of rivers and springs were measured using graduated bucket at the outlets of the sub watersheds and the values were weighted to the area of the respective sub watersheds. Water productivity was explored by interviewing farmers who practiced irrigation at the lower part of each subwatershed. Data were analyzed based on standard procedures and statistical soft wares.ANOVA showed highly significant differences between untreated and treated subwatersheds for soil moisture contents at the beginning of the dry season (P ≤ 0.001) and at the most dry season (P ≤ 0.001). Statistically higher mean values of 25.92% and 27.35% were observed at 0-20 cm and 20-40 cm soil depths respectively in the treated subwatershed compared to 21.70% and 23.82% in the untreated subwatershed during the beginning of the dry season; and higher mean value of 10.16% was recorded at the treated subwatershed compared to 9.50% in the untreated subwatershed during the dry season (January) at 0-20 cm soil depth. Soil moisture content was not affected by landscape positions and land use types at the study area. In addition soil moisture was positively correlated with plant species diversity, plant biomass production, and soil organic carbon. Furthermore, highly significant difference was observed for dry season base flow with a mean value of 1.99 Ls^-1 at the treated subwatershed compared to the man value of 0.27 Ls^-1 in the untreated subwatershed. Due to increased base flow, irrigable land increased and crop production shifted from less water demanding and less productive pulses to higher water demanding and higher productive vegetables at the treated subwatershed. Thus, it can be concluded that sustainable land management interventions at Geda watershed brought positive impacts on improving soil moisture content and base flows; therefore, we recommend sustaining and expanding the practices to other watersheds as well.

Keywords: Discharge, landscape position, land use, soil moisture content, subwatershed

DOI: 10.7176/JEES/12-5-03

Publication date:May 31^st 2022