Water resources management, highlighted in the No 1 central document issued in January, will in all probability be discussed at the annual sessions of the National People's Congress and the Chinese People's Political Consultative Conference.

Water resources management is very important for China because the per capita availability of water in the country is about one-third of the world average. Per capita water availability in rain-starved northern China is only one-fourth of that in the southern parts. Many rivers and lakes have dried up in the northern parts, seriously degrading the environment. Yet the north is where almost half China's population lives, and where most of its corn, wheat and vegetables are grown.

Water is even scarcer in the western parts of China, which has few water sources to meet people's demands. The economic development of the region partly depends on over-exploitation of surface and groundwater sources.

China's leadership is well aware of the deepening water crisis. It has decided to accelerate water reform and development, and proposed the most stringent measures for water resources management. These measures are aimed at limiting the total use or drawing of water, increasing water-use efficiency, and reducing the amount of pollution loads. Enforcing these measures is very challenging and the government's statement that leaders at various levels will be held accountable makes it even more so.

Follow-up work needs to be carried out to make the proposed measures more effective. Experiences and lessons from China and other countries suggest that limiting the use or drawing of water, or increasing water-use efficiency may increase rather than reduce the consumptive use of water, particularly in water-scarce areas.

Over the past two decades, China has spent huge funds in rural areas to introduce irrigation water savings programs. The programs focus on reinstating irrigation and drainage systems and promoting various water-saving technologies to increase effective irrigated areas by raising the level of water-use efficiency.

But statistics show that over the past 30 years the effective irrigated area has increased by about 8 million hectares, while the total use or drawing of water has remained much the same and the annual over-exploitation of groundwater has reached up to 22 billion cubic meters. As a result, the eco-system in these areas has degraded further.

Saving water under the traditional concept is to reduce supply and application losses, for example by lining canals, using pipes and installing sprinkler or drip irrigation. This reduces water that is "lost" when measured at point of diversion to point of delivery and field "losses", which many water officials consider water available for expanding irrigated areas or transferring to domestic or industrial uses.

But this water is not totally lost nor are the savings "real"; most of the water that "escapes" returns to the water system through run-off or percolation and can be reused again. But this "lost water" has a cost when measured and paid for as well when energy is used to divert, deliver and apply it.

As a special report on water in the Economist (May 20, 2010) said, "In truth, though, such water is not all lost: much of it returns to the aquifers below, from where it can be pumped up again. There is a cost to this, in energy and therefore cash, but not in water. The only water truly lost in a hydrologic system is through evapotranspiration (ET), since no one can make further use of it once it is in the atmosphere."

If genuine savings are to be made, measures should be taken to cut non-beneficial ET or reduce ET (for example, by reducing irrigated areas or producing food with less transpiration). Growing more crops over a wider irrigated area or increasing of cropping intensity in the same area raises the level of ET.

In many water-scarce areas in the world that are similar to North China, policies aimed at reducing the use or drawing of water have actually increased groundwater depletion. This has happened in the Upper Rio Grande basin shared by the United States and Mexico, where measures designed to make irrigation more efficient have increased crop yields upstream, which in turn have raised the level of ET and left less water to replenish aquifers.

Such facts increase the attractiveness of demand management that is being tried in China. In irrigation projects that cover several parts of arid and semi-arid areas, including Water Conservation Project, GEF Hai Basin Integrated Water and Environment Management Project and the Xinjiang Turpan Water Conservation Project, the World Bank has been promoting water conservation with focus on reducing consumptive use of water or ET.

As part of the Water Conservation Project, farmers have formed water-users' associations to plan and operate irrigation services. But the objective is specifically to reduce consumptive use of water or ET and simultaneously increase the farmers' incomes (for example, by using integrated engineering, and agricultural and management measures such as crop pattern adjustments) without further depleting the groundwater table. The objective is also to increase the yield and value of production per unit of ET and stay within the fixed consumption quota.

According to project monitoring data, the farmers' per capita income increased by 193 percent and water productivity rose by 82 percent, while consumptive use of water or ET over the irrigated areas fell by 27 percent by the end of the Water Conservation Project (2000-2006), which was financed by the World Bank and implemented by the Ministry of Water Resources. The project shows that the main strategic goal of combating water scarcity is to find better ways to reduce the consumptive use of water or ET, and increase farmers' incomes in addition to many other good measures.

The author is a senior irrigation specialist at World Bank.