Evaluation of Rain Water Harvesting Systems for coping water shortage in the Upper Blue Nile Basin, North West Ethiopia

Abstract

Background The applicability of rainwater harvesting structure is very poor while the intended purpose is achievable in the Blue Nile basin. Therefore, this research was initiated to evaluate the performance of a rainwater harvesting structure and put possible strategies for dry season challenges. The study carried out for three years in the North West Ethiopia. Methods The data were analyzed using daily water balance model and other performance indicators (number of water day, relative irrigation supply, runoff storage efficiency and marginal rate of return). Results At the inception, it was established that the existing rain water harvesting system performs very low, runoff storage efficiency below 46%, no zero water day above 50%, relative irrigation supply below 27 % and marginal rate of return from 12 to 65%. However the greater the volume of the rain water harvesting structure the higher runoff storage efficiency, higher relative irrigation supply, and lower no water day under different irrigation technique was achieved. Conclusions For attaining household irrigation water demand in the dry season, the user should adopt storage capacity of 630m3 in Nitisol and 361m3 in Vertisol for double cropping and 273 m3 in Rigosol for supplemental irrigation. Hence, applying rainwater harvesting technologies with efficient water management technique enhance the net benefit of the system.