The world's growing population and changing consumption patterns will continue to drive demand for food. While the basic water needs of humans and animals are relatively small, it is the production of food and fibre crops that claims the dominant share of water abstractions. These abstractions are consumed through evapotranspiration from crops and soils or returned to watercourses and aquifers as drainage. The net result is that while the daily need of drinking water per person is 4 litres, the water required to produce our daily food is considerable higher, essential requirements are 1000 litres per day but depending on our dietary preferences can vary between 2000-5000 litres.
In addition, it should be remembered that that demands for food and potable water are non-negotiable, so that the primary opportunity for improving overall water management will hinge on the continued improvement of water productivity in existing agricultural systems (rainfed and irrigated).
Agriculture is by far the biggest user of freshwater, accounting for a global average of 70 percent of all water withdrawals. Irrigated agriculture today, occupies less than 20 percent of the cultivated land, but produces 40 percent of the world food supplies and almost 60 percent of cereal production in the developing world. In this sense improved agricultural water management remains the only option for achieving food security. FAO's recently published World agriculture: towards 2015/30 (herein referred to as AT2030) projects that global food production will need to increase by 60 percent to close nutrition gaps, cope with the population growth and accommodate changes in diets. It is anticipated that agricultural water withdrawal will increase by some 14 percent from 2000 to 2030 in order to meet these food production needs. The report anticipates a net global expansion of arable irrigated land of some 45 million ha (a total of 242 million ha in 2030), with significant regional disparity). This reflects a projected annual growth rate, in water use, of 0.6 percent, compared with the 1.9 percent observed in the period 1963-1999.
But global totals and averages mask reality since water management questions are generally addressed at local level. Data by country already give a better picture, although in large countries the national totals and averages still hide wide regional differences. The Near East, North Africa and parts of Asia are subject to water stress, when compared with the relative abundance of land and water resources in Latin America, and the low percentage of irrigated agriculture in sub-Saharan Africa. Indeed, lack of investment in productive agriculture can present as many limits as lack of natural resources.
For 93 developing countries, the water use efficiency in irrigation (the ratio between the consumptive use of water by crops and the total amount of water withdrawn) is expected to grow from 38 to 42 percent. However, there are major regional differences: higher efficiencies are reached in the water-scarce regions, while water-rich regions are not expected to make similar gains.
