The first part of my article talked about four of the five measures that should be taken to meet the demand for water. The last but definitely not the least is ecological safety, including ecological restoration and reducing water pollution.

The annual discharge of industrial wastewater and sewage in cities and township increased from 23.9 billion cubic meters in 1980 to 73.1 billion cu m in 2006. A huge volume of untreated wastewater is still being discharged into rivers.

As a result, water pollution has worsened in most rivers and lakes. Based on the evaluation of 140,000 km of rivers across the country in 2006, the quality of water in 41.7 percent of the stretch was class IV or even lower, and in 21.8 percent, below class V.

To reduce water pollution, we should develop a green economy at the macro-level by changing the existing model of economic development and building a recycling economy at the interim level by developing a pollution-prevention society and controlling pollutant discharge. And at the micro-level, we have to adopt cleaner production methods.

About 3.56 million sq km, or 37 percent of the country's land area, suffers from soil erosion. In absolute figures, 5 billion tons of soil is lost every year. Serious soil erosion not only harms agriculture, but also aggravates ecological degradation and sedimentation of rivers, leading to more floods in their lower reaches.

Typical examples of ecological degradation are drying up of rivers and lakes, shrinking of wetlands and disappearing of oasis.

In recent years, great importance has been attached to water and soil conservation. An integrated approach has been taken by using small watersheds as management units, and emphasis has been laid on self-recovery of ecosystems. For rivers and lakes with fragile ecology and damaged environment, the focus has been on steps to optimize water resources allocation, transfer of water for ecological purposes, and ecological protection, improvement and restoration.

Thanks to such measures, dry beds have not been seen on the Yellow River in the past nine years. The projects to divert water from the Yellow River to Tai Lake and to supply the Pearl River with more freshwater to maintain a steady flow to prevent seawater invasion have been implemented. These moves have helped improve ecology of rivers and lakes.

We have to build a water-saving and pollution-preventing society if we want to achieve sustainable use of water resources.

Shortage of water and its uneven distribution are a big challenge for China. The normal practice is to build reservoirs to balance water distribution in seasons and divert water from rivers to balance the uneven water distribution in regions. But these two measures alone cannot solve the problem. Building a water-saving society is a more effective and strategic way of doing that.

We need to set up a water-conserving mechanism with economic ends in mind. A water resources management system, based on the theory of water entitlement, should be established to encourage water conservation, make people use water more efficiently and harmonize the economic development with environmental protection.

Indices at the macro- and micro-level for the use of water have to be clearly identified. For that we need to perfect our water pricing system and set up market rules for water trade. And the government has to issue regulations on a market-oriented water management mechanism with public participation.

The Ministry of Water Resources (MWR) has already issued the Interim Measures for Water Quantity Allocation and Management Method of Water Abstract Permit. Seven river basin commissions have worked out the control index for the maximum quantity of water that can be abstracted. The water allocation index of the Yellow River has specified the volumes even for its tributaries, with Jiangxi becoming the first province to complete water allocation index for its major rivers and lakes.

The Yellow River Conservation Commission (YRCC) has approved 26 water entitlement-trading programs in the Ningxia Hui and Inner Mongolia autonomous regions, with the water trading volume reaching 228 million cu m. Twenty-seven provinces, autonomous regions and municipalities have issued documents on the quota of water that can be abstracted. And devices to measure the use of water have been installed in about 90 percent urban houses and other establishments.All these bode well for water conservation.

If a water-saving society in needed for conservation of water, then a prevent-water pollution society has to be developed to reduce water pollution. Based on function zoning of river management bodies, we have to charge organizations and enterprises for discharging pollutants. Economic means such as quota management, pollution-discharge license trade and wastewater discharge fees should be used to reduce water pollution.

The MWR has approved function zoning of rivers in all 31 provinces, autonomous regions and municipalities on the Chinese mainland and set a limit on pollutant discharge into the mainstreams of the Yellow, Huai, Hai, Songhua, Liao and Pearl rivers, the Taihu Lake and Three Georges Reservoir in Yangtze River basin. Work on and registration of pollutant discharge outlets in seven major river basins is complete. And a master plan to safeguard cities' drinking water sources has been prepared, and a list of 118 national key drinking water sources, published.

Water shortage and water pollution are the greatest threat to water safety. Recently, the MWR proposed stricter a water resources management system. Implementing such a system means laws and regulations have to be applied effectively and improved continuously by identifying "red lines" for water use, efficiency levels and water pollutants.

The first "red line" should define the use and exploitation of water by means of optimized water resources allocation, conservation and protection. The second should define the pollutant carrying capacity of water bodies, and controlling the volume of pollutants discharged into them. The third should define water use efficiency by reducing the waste of water.

The government is studying and exploring a scientific water resources management system. And we have every reason to believe the country will be able to overcome the difficulties posed by water shortage, and ensure sustainable development of the economy and society.

The author is former Minister of Water Resources. The article is second part of his keynote speech at last week's international symposium on water security held by China Institute for International Strategic Studies.

(China Daily June 2, 2009)