Water For Crop Production

Rainfall contributes to an estimated 65 percent of global food production, while the remaining 35 percent of global food is produced with irrigation. In most parts of the world, rainfall is, for at least part of the year, insufficient to grow crops, and rainfed food production is heavily affected by annual variations in precipitation.

A major part of the developed global water resources is used for food production. In most countries, 60 to 80 percent of the total volume of devel oped water resources is used for agriculture and may reach well over 80 percent for countries in arid and semiarid regions (Smith, 2000).

Irrigation is an obvious option to increase and stabilize crop production. Major investments were made in irrigation during the latter half of the twentieth century by diverting surface water and extracting groundwater. The irrigated areas in the world, during the last three decades of twentieth century, increased by 25 percent (FAO, 1993). The expansion rate has slowed down substantially because a major part of the reliable surface waters have already been developed, while groundwater resources have become overexploited at an alarming rate.

With water resources becoming scarce, waters of inferior quality are increasingly used. Excessive use and poor management of such irrigation water has had, in some cases, detrimental effects on soil quality, causing whole areas to be taken out of production or requiring the construction of expensive drainage works. Defining strategies in planning and management of available water resources in the agricultural sector will become a national and global priority.

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