The measure taken to secure stable increase in food production is expansion of the irrigated area of farmlands. Not even half the farmland area of China has so far been irrigated, but that irrigated area accounts for two-thirds of national food production. The irrigated farmland area in China is the largest in the world, and the demand for agricultural water is extremely high. However the expansion of irrigated farmland area is constrained by shortage of water resources, which is a critical constraint on sustainable and stable growth of food production. Per-capita water resources in China are merely a quarter of the world average level, and the average amount of irrigation water for farmlands also is only half of the world average. In other words, the water shortage situation in the country is extremely severe. In addition to insufficient water-resources, China also possesses the following features.
(1) Agricultural demand for water is considerable. Of 476.7 billion cubic meters of national water resource per year, 419.5 billion cubic meters or 88% is used for agriculture, mainly for irrigation purposes.
(2) Regional distribution of water is quite uneven - much in the south and a little in the north. The areas to the south of the Changjiang River have some 70% of national water resources, but only 31% of national farmland area. Those to the north of the river, on the other hand, possess about 30% of the national water resources, but as much as 69% of the national farmland area. The water resource per capita contained in the south-west region amounts to as much as 38,400 cubic meters, fifteen times the national average, whereas average per capita and farmland water-resources in the vast northern regions with their high populations are much lower, with as little as 430 cubic meters per capita in some areas.
(3) Seasonal and annual changes in rainfalls are extraordinarily great, frequently causing flood and drought damage. The highest annual precipitation is two to four times the lowest in the southern regions. The highest in the north is three to six times the lowest in those regions.
