Abstract
Extreme rainfall variability has been one of the major factors to famine and environmental degradation in Ethiopia. The potential for water harvesting in the Upper Blue Nile Basin was assessed using two GIS-based Multicriteria Evaluation methods: (1) a Boolean approach to locate suitable areas for in situ and ex situ systems and (2) a weighted overlay analysis to classify suitable areas into different water harvesting suitability levels. The sensitivity of the results was analyzed to the influence given to different constraining factors. A large part of the basin was suitable for water harvesting: the Boolean analysis showed that 36% of the basin was suitable for in situ and ex situ systems, while the weighted overlay analysis showed that 6–24% of the basin was highly suitable. Rainfall has the highest influence on suitability for water harvesting. Implementing water harvesting in nonagricultural land use types may further increase the benefit. Assessing water harvesting suitability at the larger catchment scale lays the foundation for modeling of water harvesting at mesoscale, which enables analysis of the potential and implications of upscaling of water harvesting practices for building resilience against climatic shocks. A complete water harvesting suitability study requires socioeconomic analysis and stakeholder consultation.
Highlights
Rainfed agriculture will remain the dominant source of staple food production and the basis for livelihoods of the majority of the rural poor in Ethiopia [1, 2]
The Upper Blue Nile Basin of Ethiopia occupies an area of 199,812 km2 and is located within eastern and central Ethiopia [44]
In the Ethiopian setting we suggest that this argument is not applicable, as most farmers already cultivate degraded soils, and that farmers are entirely dependent on this agriculture for their livelihoods
Summary
Rainfed agriculture will remain the dominant source of staple food production and the basis for livelihoods of the majority of the rural poor in Ethiopia [1, 2]. Extended dry periods in combination with more frequent storm floods, a rugged topography and high population pressure has caused large soil erosion and land degradation in the highlands of Ethiopia [8,9,10]. These degradation processes have been aggravated by intensive farming and livestock grazing. The biodiversity and environmental health of aquatic ecosystems are seriously threatened by the land degradation on agricultural lands [11] Such degradation is likely to affect the local hydrology, resulting in reduction of evapotranspiration fluxes during the rainy season. This in turn affects the feedback of moisture to the atmosphere, which reduces the recycling of moisture and thereby may reduce the rainfall further inland [12,13,14]
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