Most parts of the country have approximately 70% of annual rainfall in a maximum of four months. The rate exceeds 80% in the northern plains. These characteristics, marked by considerable annual changes in and seasonal high concentrations of precipitation, have caused a number of large-scale droughts and floods. These are major factors in the instability of Chinese agricultural production. Therefore, construction of irrigation facilities to cope with droughts and floods is one of the great critical objectives the country's agricultural sector must attain.
(4) The effective utilization rate of water resources is relatively low. The effective utilization rate of irrigation water in farmlands is about 40 to 65%.
Water is the major problem impeding agricultural development in China in the 21st century. Confronted with this problem, the country's agricultural policies for the next century emphasize the following measures. The first measure is aimed at reinforcing irrigation-related construction. Large- or medium-scale irrigation projects to go beyond this century will mainly consist of irrigation works at rivers and lakes. This measure includes constructions in the Changjiang Sanxia Project, the Huang He Xiaolangdi Project, and the Sichuan Ertan Project to improve the capability of coping with floods and droughts. Once in place, these works will significantly enhance the ability, needed in agricultural production, to withstand natural disasters and to overcome the shortage of agricultural water in the 21st century. The second measure will build up basic agricultural facilities for the expansion of the irrigated area, focusing on irrigation for farmlands. Irrigation systems will be introduced to improve production conditions, aiming at an upsurge in agricultural production. The third measure is directed towards wide diffusion of water-saving irrigation technologies. On the basis of an estimate of roughly 450 billion cubic meters of national agricultural water resource, a 10% increase in the effective utilization rate of water could supply an additional 45 billion cubic meters of water per year, equivalent to the construction of dozens or even over a hundred large dams. The introduction of these measures will benefit China's agricultural development and secure increases in food production, and also alleviate the problem of water-resource shortage.
