Environ. Sci. Technol. 2009, 43, 240–244
Meeting China’s Water Shortage Crisis: Current Practices and Challenges HEFA CHENG* Tongji University, Shanghai YUANAN HU Stanford University JIANFU ZHAO Tongji University, Shanghai
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China needs to and is undertaking several initiatives to conserve its water supply for human health and national productivity.
An adequate supply of freshwater is critical to the health, economy, and environment of any country and its people. Although China ranks sixth in the world in total water resources (2.8 trillion m3), the annual per capita renewable 240
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freshwater availability is only 2300 m3, or 25% of the world’s average (1). With the world’s largest population and the second-largest national economy, water shortages in China could shake world food security and threaten global prosperity. The water challenge in China is primarily driven by the intersection of demographics and climate. China suffers from a common problem faced by many countries: too much water in the “wrong” place and time, viz., the uneven spatial and temporal distributions of water resources. As shown in Figure S1 (Supporting Information), the annual precipitation gradually declines from >1600 mm/year in the coastal provinces of the southeast to 350 L/day for Japan and the U.S., the consumption in urban China is only 212 L/day and but 69 L/day in rural areas (1). Currently 46% of China’s population lives in cities and demand for water supply is expected to increase significantly as urbanization continues. Figure 1 shows the water supply and trends in total water withdrawal and population in China. Water use has increased steadily with population from 1980 to 2006. The population in China is expected to peak in 2030, when the annual per capita renewable freshwater availability will drop to 1760 m3sonly ∼4% higher than the water stress threshold of 1700 m3/year suggested by Falkenmark and Widstrand (4). Besides taking actions against water pollution, China is aggressively undertaking multiple approaches to cope with water shortages (Table 1). In this Feature, we briefly sum10.1021/es801934a
2009 American Chemical Society
Published on Web 01/13/2009
Improving the situation. Water use efficiency is rapidly becoming the primary means of balancing limited water supplies with growing demands in China. In 2005, the government issued a comprehensive policy outline to guide the development and application of water conservation technologies and to improve the legislative and administrative management of water conservation (8). The water use per 10,000 Yuan GDP in 2006 was 329 m3, three times the world’s average and six times that in the U.S. and other developed countries (1). The Chinese government aims to cut this by 20% between 2006 and 2010 (9). By 2010, the national integrated irrigation water use efficiency is to be raised to 50% while the water consumption per 10,000 Yuan industrial output (value added) should be lower than 115 m3 (9). Watersaving devices will be fully implemented in all urban areas and water pricing will be based on supply and the cost of delivery. Annual water savings in 2010 are expected to reach 20 billion m3 for agriculture, 13.4 billion m3 for industry, and 1.8 billion m3 for household use (9).
Water Reservoirs and Inter-Basin Water Diversion
FIGURE 1. China’s water: (a) total supply by sources from 1997 to 2006; (b) trends in total withdrawal by use categories and population starting in 1980 and projected up to 2030. Data from refs (1) and (5). marize the conservation, water diversion, and alternative resource development measures taking place in China and their development in the near future. The benefits and drawbacks of different approaches to relieving water scarcity are discussed, and strategies on meeting the water challenge(s) in China are proposed.
Water Conservation and Efficiency Agricultural water. Agricultural use claims more than 60% of China’s water. Water shortages in important grainproducing regions may seriously compromise China’s agricultural production potential. To curtail this threat, the government has invested heavily in implementing watersaving irrigation technologies. Meanwhile, changes in water management and practices, along with reforming prices and fee collection systems have been made (6). Despite such significant progress in the past two decades, there is still a big gap in agricultural water use efficiency in China compared to that achieved elsewhere in the world. Industrial water. The sustained high industrial growth rate over the last three decades has resulted in a significantly higher proportion of China’s water being allocated to industrial production: use more than doubled from 10% in 1980 to 23.2% in 2006. In response, technical innovations for industrial water conservation, recycling, and reuse are being implemented. However, reports show that industrial water use in China is still far from efficient (1). Household water. Nearly 67% of the 660 cities in China face water shortages with 108 of them in severe water distress. In rural areas, >20 million people have a shortage of drinking water supplies. Water conservation is vital to relieve the household water demand. As with agricultural practices, in addition to strengthening the regulations on conservation, the Chinese government is reforming water pricing to encourage more sustainable household water usage. Quota systems have also been adopted in some cities to alleviate water shortages (7).
The extreme monsoon climate in China creates alternating drought and flood periods, so reservoirs and dams play a vital role in the effective management of surface water resources. China has the greatest number of large dams in the world, including the world’s largest, The Three Gorges Dam, with a 39.3 billion m3 reservoir. To resolve the uneven spatial distribution of water resources among basins, large water transfer infrastructures have also been constructed in China. Water shortage in one of the most water-stressed regions, the North China Plain, is relieved by several completed major interbasin water transfer projects, including diversions from the Yangtze River to the Huai River (constructed in 1961); from the Luan River to Tianjin (constructed in 1982); and from the Yellow River to Qingdao (constructed in 1986) (10). Major interbasin transfers will continue to be a significant feature of China’s future water resource development. The government has initiated the South-to-North Water Transfer Projectsthe largest of its kind ever undertaken. This will divert water from the lower, middle, and upper reaches of the Yangtze River to the North China Plain and the Yellow River basin using three transfer routes. After its projected completion in 2050, China’s four major rivers, the Yangtze, Yellow, Huai, and Hai, will be linked, and 44.8 billion m3 of water will be annually diverted, allowing adjustment and allocation of nearly 10% of the nation’s surface water resources (11).
Alternative Water Resources Rainwater harvesting. With some basic infrastructure, rainwater can be collected and stored for future use. Rainwater harvesting has been widely promoted to address shortages in the semiarid loess regions, particularly for agricultural and household use (12). Urban centers in northern China also practice rainwater harvesting. Realizing that rainwater is still under-utilized as a crucial water resource, China has made rainwater harvesting a top priority in the semiarid and arid regions (12). Precipitation enhancement. Precipitation enhancement (cloud seeding) has emerged as a solution to alleviate the frequent droughts in north and northwest China. China is foremost among more than 20 countries that practice precipitation enhancement. China considers this as one of the technologies capable of augmenting freshwater supplies and so continues to invest in the research and operation of this technology (13). Seawater utilization. Some 40% of China’s population lives in the 11 coastal provinces that form but 15% of the country’s land area. These coastal provinces account for VOL. 43, NO. 2, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Comparison of Alternatives to Meet the Demand for Water in China alternative
capacity in 2006a, billion m3 (1, 24)
status in China (2006 or earlier as noted)
water conservation and efficiency
N/A
low agricultural water use efficiency: 38% for national integrated irrigation; mean irrigation water consumption in China up to 6735 m3/ha/year in 2006 (1); inefficient industrial water use: for value added (at production stage), water consumption was 178 m3/10,000 Yuan; industrial water recycling rate was 60-65% vs 0.1 billion m3) and 2865 medium (0.01-0.1 billion m3) dam reservoirs; accounts for 34.5% of surface water supply (1); interbasin water transfer contributed 11.8 billion m3, or 2.5% of the surface water supply (1).
rainwater harvesting
1.3
widely promoted for agricultural and household uses in semiarid loess regions since the 1980s; by 2001, about 12 million water cellars, tanks, and small ponds built with total storage capacity of 16 billion m3; supplying water for household use of 36 million people and supplemental irrigation for 260 ha of dry farming land (20); practiced in northern China cities; collected rainwater used for toilet flushing, landscape irrigation, car washing, and aquifer recharge.
precipitation enhancement
N/A
regularly practiced in semiarid and arid regions to augment freshwater supplies; from 1995 to 2003, 23 provinces conducted precipitation enhancement operations; covered more than 0.3 billion ha of land; total rainfall volume of 210 billion m3 (21).
seawater utilization
direct utilization 26.9 desalination 0.05
>20 seawater desalination plants with 30-5000 m3/day capacities in operation in 2005; produced 31,000 m3/day total desalinated water (22); brackish water desalination capacity 28,000 m3/day in 2005 (14); seawater directly utilized as cooling water at power plants and for industrial applications; seawater used to flush 75% of toilets in Hong Kong (23); actively introduced for toilet flushing in several coastal cities.
municipal wastewater reclamation
1.0
popular in water-stressed northern China cities; only nonpotable reuse practiced; reclaimed wastewater used primarily for landscape irrigation, toilet flushing, lake and river augmentation, and industrially; still in infancy in China; only 4% of the 24.4 billion m3 of discharged municipal wastewater reclaimed (24).
a
Data compiled from refs (1) and (24). N/A ) data not available.
approximately 67% of China’s GDP, yet the annual per capita renewable freshwater availability is only 1266 m3, or
