Abstract
Soil erosion in Ethiopian highlands has caused land deterioration due to moving nutrient-rich top soil to downstream reservoirs while leaving reservoirs dysfunctional due to sedimentation. Micro-watershed management by removing reservoir sediments and using them for reclaiming farmland, while using reservoir water for irrigation, can be a potential solution to simultaneously address soil and water constraints and food security challenges. Still, there is knowledge gap before such a solution can be practically applied. The objective of this paper is to present potential solutions for the reservoir sedimentation problem and specifically highlight the utility of bathymetric survey using an echo-sounder to assess sediment volume. Our results indicated that the estimated reservoir sediment volume was 6400 m3 leading to a reclamation of 3.2 hectares by layering 0.2 m sediment. The sediment used for reclamation depicts neutral pH (7.3), high organic carbon (2.5%), available phosphorus (9.2 mg/kg) and exchangeable potassium (25 cmol(+)/kg). Garlic (Allium sativum) was planted in the reclaiming abandoned farmland and produced 7.1 t/ha of bulb on average. There is a potential of producing 2–3 horticultural crops per year. Thus, developing methods for scaling up potential farmland reclamation using reservoir sediment would contribute to degraded farmland restoration and food security in Ethiopia and beyond.
Highlights
The Federal Democratic Republic of Ethiopia is located in the eastern part of sub-Saharan Africa
The objective of this paper is to present potential solutions to solve the reservoir sedimentation problem in Tigray by presenting a case study of the Adizaboy reservoir in Tigray and documenting the engineering process of implementing farmland reclamation
Many reservoirs have been constructed, numerous reservoirs located at the outlet of the micro-watershed experience the problems of sediment accumulation [2,22] and water leakage [8]
Summary
The Federal Democratic Republic of Ethiopia (hereinafter Ethiopia) is located in the eastern part of sub-Saharan Africa (latitude: 3–14◦N, longitude: 33–48◦E). Its landscape is divided by the Great Rift Valley of Africa, a continuous trench that runs through the country in a northeastern-southwestern direction and characterized by diverse agro-ecological systems that greatly vary with topographic elevation, ranging from 125 m below sea level to 4620 m above sea level. Ethiopian highlands in the western part of the Great Rift Valley feature a tropical climate, while those located around the perimeter of the Valley can be classified as semi-arid areas. The Tigray region is a typical Ethiopian highland, characterized by chronic droughts due to irregular rains, which cause frequent harvesting failures. While inhabitants in the highlands of Tigray grow wheat as a staple food, the wheat sowing to tillering period, during which uncovered bare soil is exposed to erosion, coincides with the rainy season for about three months, resulting in massive soil erosion. Subsequent soil nutrient loss through surface runoff is responsible for low crop productivity and chronic food insecurity in the region
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