Beijing, the capital of China, is characterized by intense water scarcity during the long dry season as well as heavy flooding during the brief wet season. Beijing is one of the most water-scarce cities in the world. Total water use is 3.6 billion cubic meters, compared to renewable fresh water resources of about 3 billion cubic meters. The difference is made up by the overexploitation of groundwater. Two-thirds of the water supply comes from groundwater, one third from surface water. Average rainfall has substantially declined since the 1950s. Furthermore, one of the two main rivers supplying the city, the Yongding River, had to be abandoned as a source of drinking water because of pollution. Water savings in industry and agriculture have compensated for these losses and freed up water for residential uses.
Water tariffs have been increased to provide an incentive to curb residential water demand, but the impact has been limited. Residential demand increases due to population growth, and the city taps new water sources. For example, water reclamation has been aggressively promoted since the turn of the century. The city's 15 central municipal wastewater treatment plants and more than 300 small, decentralized plants now provide reclaimed water for non-potable uses. An additional 1.2 billion cubic meter is expected to be provided through the southern section of the South-North Water Transfer Project's central route from the Han River, more than 1,000 km to the south, until the end of 2014. The supply of desalinated seawater from existing desalination plants near Tianjin is also being contemplated.
Climate and population
Annual average precipitation in Beijing is only 578 mm, compared to 1,090mm in New York City. There is virtually no rain from September to April. About 60% of rainfall occurs in only two summer months. In dry years, precipitation can be as low as 242 mm, recorded in 1869. There has been a long-term decline in precipitation, with an average of only 428 mm recorded in the period 1999–2008. Beijing municipality covers an area of more than 16,800 square kilometers, roughly half the size of Belgium, including the city of Beijing and surrounding rural areas that account for most of its area and about a third of its population. As of 2010 the municipality had almost 20 million inhabitants, up from 10.8 million in 1990.
Water resources
Historically, since the Yuan dynasty Beijing received its water mainly through canals from springs in the mountains north and west of the city, feeding a system of lakes designed by Guo Shoujing. This allowed the city to thrive although it was located far from a major river. However, the yield of these springs declined as a result of deforestation and the springs do not supply Beijing with water any more. They were replaced by groundwater and by reservoirs from dams built during the 1950s in the areas surrounding Beijing as the major sources of water supply for the city.
Beijing has about 150 cubic meters of water resources per capita, making it a water-stressed city.
Groundwater
Today the major water source for Beijing municipality is groundwater, which accounts for about 75 percent of water use. The safe yield of the aquifer is estimated at between 2 and 2.5 billion cubic meter per year, depending on rainfall. Thus abstraction is greater than the replenishment of the aquifer, resulting in a decline of the groundwater table that causes the sinking of ground surface (i.e. land subsidence). In addition, groundwater infiltration has declined because urban areas have been increasingly built up, sealing the surface.
For municipal water supply, the share of groundwater is much lower and the share of surface water is much greater. In 2009 Beijing had 19 water treatment plants, including many relatively small ones that treat groundwater, while surface water treatment plants are much larger.
Surface water
Small to medium-sized rivers provide the remaining water resources for Beijing municipality in the amount of 1 billion cubic meter per year during the 1980s and 1990, down from about 2 billion cubic meter per year during the 1960s and 1970s for all uses, including agriculture. By comparison: The Hudson River in the United States carries almost 20 billion cubic meter in an average year, 20 times as much as the rivers in Beijing municipality. The Yangtse River carries about 600 billion cubic meter per year, 600 times as much.