The source of life and a precious resource for agriculture
Water is essential for economic and social development. Although a large part of the earth’s surface area is covered by water, water is only an exploitable resource when it is suitable for consumption either by humans, industry or agriculture. Most of the utilized freshwater goes toward agricultural purposes, like irrigation. In fact, agriculture accounts for 70 percent of all withdrawals, a figure that increases to 95 percent in developing countries.
Use of water in food and agriculture Food and agriculture are the largest consumers of water, requiring one hundred times more than we use for personal needs. Up to 70 % of the water we take from rivers and groundwater goes into irrigation, about 10% is used in domestic applications and 20% in industry. Currently, about 3600 km3 of freshwater are withdrawn for human use. Of these, roughly half is really consumed as a result of evaporation, incorporation into crops and transpiration from crops. The other half recharges groundwater or surface flows or is lost in unproductive evaporation. Up to 90% of the water withdrawn for domestic use is returned to rivers and aquifers as wastewater and industries typically consume only about 5% of the water they withdraw. This wastewater from domestic sewage systems and industries should be treated before being dismissed.
Since the 1960s the global nutrition has considerably improved, providing more food per capital at progressively lower prices. This performance was possible through high-yielding seeds, irrigation and plant nutrition. As population keeps increasing more food and livestock feed need to be produced in the future and more water applied to this purpose. Irrigate agriculture will have to claim large quantities of water to produce the food required to feed the world. The main source of food for the population of the world is agriculture: this term also includes livestock husbandry, manages fisheries and forestry. For vegetative growth and development plants require water in adequate quantity and at the right time. Crops have very specific water
requirements, and these vary depending on local climate conditions. The production of meat requires between six and twenty time more water than for cereals.
Irrigated farm land doubled over last 50 years While the daily drinking water requirement per person is only two to four liters, the production of 1000 kilojoules of food requires on average 83 liter of water. For example, one apple takes 70 liters of water to be produced. However, calculating and assessing the water use for food
production is difficult, as it depends on the source / origin of water and the local water availability. It is important to make the distinction between rain-fed agriculture – farming that depends on natural rainfall – and irrigated agriculture. Irrigating land changes the natural water cycle, through withdrawal of water from surface or groundwater and use for growing crops in intensive systems. Rain-fed agriculture in contrast
relies on the natural climate conditions and has no direct impact on the water cycle; it is therefore more vulnerable to the impact of adverse weather and climate change and tends to be less productive.
Irrigation has made a huge contribution to providing a stable food supply for the world’s population. Over the last 50 years, the Earth’s population has doubled, with the global food system responding remarkably to this increase in food demand. While total cropland increased by 12 percent only over this period, the irrigated area doubled, accounting for most of the net increase of food production.
The irrigation level varies from area to area, mostly depending on climate conditions and on the development of irrigation infrastructure. The following figure shows the area equipped for irrigation as percentage of cultivated land by country.