Meeting China s Water Shortage Crisis: Current Practices and Challenges

Transcription

1 Environ. Sci. Technol. 2009, 43, Meeting China s Water Shortage Crisis: Current Practices and Challenges HEFA CHENG* Tongji University, Shanghai YUANAN HU Stanford University JIANFU ZHAO Tongji University, Shanghai ISTOCKPHOTO 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 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 2, 2009 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 <50 mm/year in the northwest. Unfortunately, the distributions of the country s population and economy do not conincide with that of the water resources. The North China Plain bounded by the Hai, Huai, and Yellow rivers has 33% of China s population and generates the same national percentage of gross domestic product (GDP) and industrial output, yet only shares 7.7% of the national water resources. Conversely, 21.3% of the country s water resources are in the southwest, but that region accounts for only 0.7% of the national GDP and industrial output (2). China has a marked continental monsoon climate in which 60-70%, and close to 80% in northern regions, of precipitation occurs during the summer. This not only makes water utilization and resourcing difficult, but also results in drought and flood disasters. Pollution exacerbates the water shortages in China. Disposal of hazardous and municipal waste, discharge of industrial and municipal wastewater, and agricultural runoff of fertilizers, pesticides, and manure have polluted most of the country s surface and groundwaters (3). A recent national water quality survey showed that only 58.3% of the river sections, 49.7% of lakes, 79.5% of reservoirs, and 38.7% of groundwater wells met the quality criteria for source water supply (1). So extensive is water pollution that even southern China, with its relatively well-stocked resources, faces shortages of safe and clean drinking water. Demand for clean freshwater is rising in China due to the increasing population, rapidly developing economic and social system, accelerated urbanization, and improvements in both the standard of living and the surrounding ecosystems. Compared to an average per capita water consumption of >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 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 sum /es801934a 2009 American Chemical Society Published on Web 01/13/2009

2 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 m 3, 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 m 3 (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 m 3 for agriculture, 13.4 billion m 3 for industry, and 1.8 billion m 3 for household use (9). 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 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 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). Water Reservoirs and Inter-Basin Water Diversion 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 m 3 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 m 3 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 9 241

3 TABLE 1. Comparison of Alternatives to Meet the Demand for Water in China alternative water conservation and efficiency N/A capacity in 2006 a, billion m 3 (1, 24) status in China (2006 or earlier as noted) low agricultural water use efficiency: 38% for national integrated irrigation; mean irrigation water consumption in China up to 6735 m 3 /ha/year in 2006 (1); inefficient industrial water use: for value added (at production stage), water consumption was 178 m 3 /10,000 Yuan; industrial water recycling rate was 60-65% vs <50 m 3 water consumption and 80-85% recycling rate in developed countries(19); National Water Conservation Week introduced in 1992; water-saving devices promoted in cities. water reservoirs and interbasin water transfer total of billion m 3 water stored in 471 large (>0.1 billion m 3 ) and 2865 medium ( billion m 3 ) dam reservoirs; accounts for 34.5% of surface water supply (1); interbasin water transfer contributed 11.8 billion m 3, 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 m 3 ; 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 m 3 (21). seawater utilization direct utilization 26.9 desalination 0.05 >20 seawater desalination plants with m 3 /day capacities in operation in 2005; produced 31,000 m 3 /day total desalinated water (22); brackish water desalination capacity 28,000 m 3 /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 m 3 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 m 3,or<60% of the nation s average (14). Desalination is an effective and important strategic approach to alleviate the shortage of water resources in coastal regions. Seawater is also directly used in some industrial and domestic nonpotable applications, increasing at a rate of approximately 2.1 billion m 3 /year since 1997 (1). China plans to desalinate nearly 1 billion m 3 of seawater/year and directly utilize 100 billion m 3 /year by 2020, meeting 26-37% of the total water demand in the coastal cities (14). Municipal wastewater reclamation. Capturing water from nonconventional sources such as industrial or municipal wastewater and restoring it to a quality suitable for various reuses is another promising solution to urban water shortages. Limited by cost factors in China, reclaimed wastewater rarely undergoes advanced treatment (e.g., reverse osmosis, activated carbon adsorption). Thus the reclaimed wastewater is currently of relatively poor quality and may pose health risks and/or fail to meet some user-specific requirements (e.g., total dissolved solids content). Despite these issues, there is a great potential for developing more municipal wastewater reclamation projects to alleviate the pressure from existing water shortages in cities. China aims to increase its wastewater reclamation capacity by 6.8 million m 3 /day between 2006 and 2010 (15). By 2010, northern Chinese cities will reuse 20% of municipal wastewater and southern cities are to reuse 5-10% (9). Prospects and Challenges Solutions to China s water shortage problems are urgently needed yet must be accomplished sustainably, economically, and safely. The advantages and limitations of different solutions to address water shortages are summarized in Table 1. Although large-scale reservoirs and interbasin transfer projects will continue to play a key role in supplying freshwater in huge quantities and balancing the unevenly distributed water resources, they cannot be a panacea for China s water crisis. Such projects involve many complex technical, economic, social, and environmental issues, and should only be treated as a supplement to water conservation and recycling efforts. Water conservation and improving usage efficiency in agriculture and industry are the most effective and sustainable solutions to water shortages. Market-driven water prices will play an increasingly important role in deterring waste and pollution (Supporting Information). Another important strategy is the utilization of alternative water resources, such as rainwater, seawater, and municipal wastewater, which should be promoted when financially possible. Because of the significant variations in demographic, socioeconomic, and water resource conditions ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 2, 2009

4 TABLE 1. Continued advantages most cost-effective and common solution; delays or eliminates need for developing expensive new water sources; reduces per capita generation of wastewater; universally applicable; potentially significant water savings. supplies large quantities of freshwater; provides flood and drought control; increases use efficiency of rainwater and river runoff; balances water resources between basins; contributes to hydroelectric power generation. low cost and simple; does not require centralized infrastructure; allows management at individual and community levels. provides drought relief to large areas; increases volume of precipitation; increases precipitation downwind of seeding area. reliable, long-term water supply; desalinated water of high quality; supply not affected by time or climate. avoids large costs of pumping, transfer, and storage; reduces environmental pollution; reliable water source with stable production rate; available at locations close to points of use and easy to access; supply not affected by climate. limitations requires investment in water-saving technology and devices; requires policy reform to provide financial incentives for saving water; practical upper limits exist. losses and damages in basin of origin; water loss during long distance transfer; weather-dependent availability; requires large investment and long construction period; requires large amounts of energy for long distance water transfer (pumping); causes conflict over water rights; future capacities may be affected by climate change. microbial contamination a major concern; proper disinfection necessary for potable use; pumping may be required; weather-dependent availability. high cost; precipitation may not be effectively utilized; limited by meteorological conditions (e.g., availability of air moisture); lack of conclusive evidence as to effectiveness. restricted to coastal regions; brine disposal is cost prohibitive for inland regions; requires large investment to modify existing systems to directly utilize; new infrastructure needed for desalination; desalination energy intensive. contaminants and pathogens in the water must be removed or decontaminated; requires separated distribution system; limited supply capacity; limited to major urban centers for good availability; requires advanced treatment (more expensive) for high quality. in disparate parts of China, one or a combination of these solutions may be necessary to meet the water demand at a reasonable cost. It is expected that changes in technology, government laws and policies, and economic factors, along with increased conservation awareness, will result in more efficient use of China s water resources (Supporting Information). Meanwhile, China faces several daunting challenges in meeting the increasing demands for clean freshwater in the near future as summarized below. Integrated water resource management. Water resource management in China is fragmented among various agencies and levels of government, including state and provincial environmental protection bureaus; the Ministry of Water Resources; the Ministry of Construction; and the Ministry of Land and Resources. This arrangement impedes optimal utilization of water resources. China must develop integrated water resource management and efficiency plans based on an interagency and multidisciplinary approach. Matching supply and demand, encouraging more efficient agricultural irrigation techniques and industrial water recycling, preventing water waste, and improving the public s awareness of conservation and protection of water resources are paramount. Additionally, the traditional water management strategies that focus exclusively on surface water and groundwater should be reformed to include nonconventional water resources and to promote their use to circumvent water scarcity. Ecosystem preservation. While maximizing economic and social welfare, allocation of water resources should not compromise the sustainability of ecosystems. Protecting and restoring ecosystems such as rivers, wetlands, and forests that naturally capture, filter, store, and release water is crucial to the supply of good quality water. China needs not only to take aggressive actions in cleaning up the polluted surface and groundwaters, but also enhance its programs in pollution prevention as proactive and cost-effective ways of dealing with pollution in the future. Water quality. A growing number of anthropogenic contaminants, including heavy metals, persistent organic pollutants, and emerging micropollutants, are increasingly found in surface, ground-, and seawaters that were previously considered clean (16). Consequently, more effective and robust treatment technologies are needed to supply clean and safe drinking water. Furthermore, these technologies need to be cost and energy effective. Energy-water nexus. Although not always apparent, energy and water are increasingly interdependent resources. Energy production requires large volumes of water and/or produces large quantities of wastewater. Further, considerable amounts of energy are needed for water conveyance, storage, treatment, and distribution. China s future water availability and quality depends on the nation s ability to continue providing reliable and low-cost energy. Already the world s second largest consumer of energy, China must actively develop alternative energy sources and advance its overall energy sustainability (17). Global warming. Global climate change will have major effects on China s future freshwater availability and water demand. The greenhouse effect is likely to increase the number of intense precipitation days and flood frequencies in northern latitudes and snowmelt-driven basins. Also, the frequency and severity of droughts could worsen as a result of a regional decrease in total rainfall, more frequent dry spells, and greater evapotranspiration (18). The vast engineered water infrastructure in China was designed and is VOL. 43, NO. 2, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 243

5 operated on the assumption that the future climate will be similar to the past. Therefore, even modest changes in climate can lead to changes in water availability outside the range of past hydrologic variability (19). Therefore, China should begin to plan for the consequences that global warming could have on its water resource distribution network and should build resilience against future uncertainties. The various measures outlined herein, if implemented properly, should help alleviate China s water shortage problems. As with any environmentally linked issue, such will depend on public awareness and effective government oversight. Supporting Information Available Additional information on China s long-term mean annual precipitation distribution, the world s major irrigation countries, irrigation water requirements for developing countries, and influences of technological innovation, government policy and economic growth on China s future water demand. This material is available free of charge via the Internet at Hefa Cheng and Jianfu Zhao are professors at the State Key Laboratory of Pollution Control and Resources Reuse, and School of Environmental Science and Engineering, Tongji University. Yuanan Hu is a research data analyst at Stanford University s Education Program for Gifted Youth (EPGY). Address correspondence about this article to Prof. Cheng at hefac@umich.edu. Literature Cited (1) 2006 China Water Resources Bulletin; P.R.C. Ministry of Water Resources; China Water Resources and Hydropower Press: Beijing, (2) Water Resources in China; P.R.C. Ministry of Water Resources: Beijing; (3) Liu, J.; Diamond, J. China s environment in a globalizing world. Nature 2005, 435 (7046), (4) Falkenmark, M.; Widstrand, C. Population and water resources: A delicate balance. Popul. Bull. 1992, 47 (3), (5) China Sustainable Development Strategy Report 2007; Chinese Academy of Sciences; Sciences Press: Beijing, (6) Lohmar, B.; Wang, J.; Rozelle, S.; Huang, J.; Dawe, D. China s Agricultural Water Policy Reforms: Increasing Investment, Resolving Conflicts and Revising Incentives; Agriculture Information Bulletin No. 782; U.S. Department of Agriculture: Washington DC, (7) The Guangdong Provincial Quotas on Water Consumption; Guangdong Ministry of Water Resources, Guangdong Development and Reform Commission, Guangdong Economic and Trade Commission: Guangzhou, China, (8) China Water Conservation Technology Policy Outline; P.R.C. National Development and Reform Commission, P.R.C. Ministry of Science and Technology: P.R.C. Ministry of Water Resources, P.R.C. Ministry of Construction: P.R.C. Ministry of Agriculture: Beijing, (9) Target for Establishing National Water-saving Society during the 11th Five-Year Plan Period; P.R.C. National Development and Reform Commission, P.R.C. Ministry of Water Resources, P.R.C. Ministry of Construction, National Development and Reform Commission: Beijing, (10) Shao, X.; Wang, H.; Wang, Z. Interbasin transfer projects and their implications: a China case study. Intl. J. River Basin Manage. 2003, 1 (1), (11) South-to-North Water Transfer Project; PRC Ministry of Water Resources; (12) The Tenth Five-Year Plan of National Rainfall Collection and Storage and 2010 Plan; P.R.C. Ministry of Water Resources, P.R.C. Ministry of Finance: Beijing, (13) Ma, J.; Guo, X.; Zhao, C.; Zhang, Y.; Hu, Z. Recent progress in cloud physics research in China. Adv. Atmos. Sci. 2007, 24 (6), (14) Special Planning Programme on Seawater Utilization; P.R.C. National Development and Reform Commission, P.R.C. State Oceanic Administration, P.R.C. Ministry Of Finance, National Development and Reform Commission: Beijing, (15) Comprehensive Energy Saving and Emission Reduction Working Guidelines; P.R.C. State Council: Beijing, (16) Shannon, M. A.; Bohn, P. W.; Elimelech, M.; Georgiadis, J. G.; Marinas, B. J.; Mayes, A. M. Science and technology for water purification in the coming decades. Nature 2008, 452 (7185), (17) Cheng, H.; Zhang, Y.; Meng, A.; Li, Q. Municipal solid waste fueled power generation in China: a case study of waste-toenergy in Changchun City. Environ. Sci. Technol. 2007, 41 (21), (18) Parry, M. L.; Canziani, O. F.; Palutikof, J. P.; van der Linden, P. J.; Hanson, C. E. Climate Change 2007: Impacts, Adaptation and Vulnerability; Cambridge University Press: Cambridge, UK, (19) Harrington, W.; Morgenstern, R. D. Economic incentives versus command and control: what s the best approach for solving environmental problems? Resources 2004, 152, (20) Khaka, E.; Malesu, M.; Oduor, A.; Mati, B. Rainwater Harvesting and the Millennium Development Goals; RELMA: Nairobi, Kenya, (21) Gao, L. Obtaining additional water from sky with precipitation enhancement. China Water Resour. News 2004, 2028, 3. (22) Zhang, L.; Xie, L.; Chen, H.; Gao, C. Progress and prospects of seawater desalination in China. Desalination 2005, 182 (1-3), (23) Li, X. Z.; Luk, S. F.; Tang, S. L. Sustainability of toilet flushing water supply in Hong Kong. Water Environ. J. 2005, 19 (2), (24) Promoting Water Conservation, Implementing Water Purification Technology, Enhancing Wastewater Treatment, and Protecting Water Safety; P.R.C. Ministry of Housing and Urban-Rural Development: Beijing, ES801934A ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 2, 2009