Subsistence rain-fed agriculture has been widely practiced for many centuries in Ethiopia and this sector has been highly dependent on rainfall. Thus, rainfall remains the crucial component of the weather elements for improving agricultural productivity. Extreme climatic conditions and high inter-annual or seasonal variability of this weather element could adversely affect productivity, because rainfall controls the crop yields and determines the choice of crops that can be grown. One of the reasons for low crop production in semi arid areas is marginal and erratic rainfall exacerbated by high runoff and evapotranspiration losses. Rainfall in terms of amount and frequency in a growing season is essential for planning and management of agricultural practices. To avert this problem, the successive Ethiopian government (from the time of Aksumite kingdom to the present) and the local community practiced different water harvesting techniques. The in-situ and ex-situ rainwater harvesting techniques have shown significant impact on improved soil moisture, runoff and ground water recharge; and increased agricultural production, which in turn reduces risks and deliver positive impacts on other ecosystems. Besides, rainwater harvesting has a potential of addressing spatial and temporal water scarcity for domestic consumption, agricultural development and overall water resources management. High water loss through seepage, lack of awareness and being very labor intensive to irrigate the whole fields by pumping the water manually from the pond and applying directly to the crop has been the main challenges of adopting harvested water technologies.
Key words: Rainfall, runoff, semi-arid Ethiopia, soil moisture, water harvesting, yield.