Water is the key input in crop production and essential to all life-human and animal. Agriculture and several of the other economic activities in sub-tropical to dry areas depend on rain. Harvesting and recycling of rain-water in dry lands are important in order to improve water use efficiency. However, about 80% of the world's agricultural land is rainfed, contributing to at least two-thirds of global food production. The rainfed areas currently account for about 60% of world food production. Farmers' yields in rainfed regions in the developing countries are low largely due to low rainwater use efficiency.