Water Resources Used in Agriculture: Historical and Global Perspectives

Globally, one-fifth of the arable land is irrigated but it contributes nearly half (47%) of the production of agricultural crops and almost three-fifth of the cereal production. Despite demonstrated socio-economic development of rural areas with intensification of irrigation, its negative impacts are also emerging in terms of increased salinization and waterlogging in surface water irrigated areas and depleting of groundwater with overexploitation and their quality deterioration. However, the challenges of meeting the projected global demand for food of ever increasing populations are monumental especially in lieu of forecasted increasing water scarcities with expected climatic variability. In addition to innovative government policies, technologies to improve irrigation efficiencies and other management issues for irrigation water supplies, enhancing the utilization of non-conventional waters is being thought as an alternative to enhance water supplies. These include rain enhancement through cloud seeding or its capture through micro-scale rainwater harvesting units and tapping offshore and onshore deep groundwater or marginal-quality waters. The marginal-quality waters mainly include saline ground/drainage and treated effluents. Their use for irrigation often leads to soil health and environmental issues. In-depth and upgraded information available for the sustainable management of saline and alkali irrigation waters at the crop, root zone, and farm levels are elaborated in this compilation.