Soil and Water Conservation Technology and Sediment Retention Assessment
Book Chapter
Leyew, SM, G/Michael, T, Mullu, A et al. (2021). Soil and Water Conservation Technology and Sediment Retention Assessment
. 315-343. 10.1007/978-3-030-76437-1_17
Leyew, SM, G/Michael, T, Mullu, A et al. (2021). Soil and Water Conservation Technology and Sediment Retention Assessment
. 315-343. 10.1007/978-3-030-76437-1_17
Soil erosion is a common menace to Ethiopian highlands. As a result, mitigation measures were practiced for decades without evaluation of the efforts made on the highlands. Therefore, this field survey was conducted in 34 community watersheds in Amhara region, Ethiopia, to determine the performance of conservation practices with respect to soil erosion and sediment retention. The study used the methodology of biophysical field surveys, and hence, different sites were selected based on agro-ecology, topography, and land use. Different types of structures were identified; vertical intervals, horizontal intervals, dimension of embankments and collection ditches’ height, width, and depth were evaluated against the standards provided by ministry of agriculture. Google earth images were downloaded, and structures were digitized for verification using field observations. Stream power index was used to delineate gullies and soil loss with two scenarios, with conservation practices (existing scenario) and without the practices (base case scenario) were estimated, and sediment retained was evaluated. Based on the results, the land affected by gullies was estimated 2% from the total land area. The gullies treated by check dams and plantation of gully sides were estimated about 54.1%. The coverage of the practices in the study watersheds accounts 60.38% and 38.02% by physical and biological measures, respectively. About 42% of the bunds were stabilized with trees and grass, and 16% of the area of community watersheds were delineated for enclosure. The gradients of bunds in humid areas where there is high rainfall, only 27.62% fits the criteria of the standard, but the remaining 72.38% were below the standard. But in most sub-humid areas where the rainfall is lower than moist humid areas, 91.25% of structures were constructed based on the recommendation. Average annual soil losses of watersheds before conservation were estimated as 77 t/ha/year and reduced to 34 t/ha/year after conservation was practiced. Thus, the amount of soil retained as a result of the practices was estimated as 43 t/ha/year, and hence 56% (0.37 cm) of soil could be engaged on land resource managed areas. From the analysis, it can be concluded that significant soil was retained as a result of implementation of practices.
