GEF

Unit 3  |  Primary Sustainability Issues 77 For irrigation systems to be sustainable, they require proper management and must not use more water than is naturally replenished—otherwise, the water source becomes a nonre- newable resource. Sustainable irrigation involves providing the precise amount of water needed for cultivation. Drip irrigation directly waters plant roots and is an increasingly widespread technique that can sharply reduce water use when compared with overhead irrigation. Water management can also be improved by install- ing “smart” control systems, such as rain sensors, soil-moisture sensors, and by making seasonal adjustments to irrigation sys- tems. In the developing world, the bulk of agricultural land is not irrigated and depends instead on rainfall. Farmers can conserve this green water by mulching, intelligent soil conservation, and using plants that are well adapted to local climates. Drip irrigation delivers water directly into the soil, reducing water lost to evaporation. Business and residential users also have an important role to play in water conservation. In many communities, water is priced so low that there is little or no incentive not to waste. Numerous utilities are initiating block pricing , in which DRIP IRRIGATION Type of irrigation in which water drips slowly to plant roots through a network of valves, pipes, or tubing, thereby saving water and fertilizers. GREEN WATER Rainwater that infiltrates soil and used for agriculture. BLOCK PRICING A water pricing structure in which users pay higher rates with higher levels of use.