Water harvesting hope for thirsty Beijing

Posted: 5 July 2006

Author: Yingling Liu

It is not sensational to predict that if China ever moves its capital city, this will be due largely to water shortages. The current capital, Beijing, is exuding dryness from every pore, particularly during the spring and autumn when it is plagued by inland sandstorms and strong winds. But now, says this China Watch report, the city is looking for new ways of water harvesting.

Beijing's aridity is taking its toll on the city¡¯s shrinking lakes, and more than 15 million residents, many of whom suffer seasonal throat aches and other health effects. While the central government hangs its hopes on huge river diversion projects in the south and city residents carefully monitor their taps, a third alternative does exist for easing Beijing¡¯s water woes: rainwater harvestng and use.

Without major rivers running through it, Beijing gets two-thirds of its water supply from groundwater. The city¡¯s per capita water availability is only 300 cubic metres a year, roughly one-eighth the national level and one-thirtieth the global level. Around 300 million cubic metres of groundwater are overdrawn annually, and as Beijing¡¯s population and water demand continue to grow, the situation is expected to only deteriorate.

By contrast, the potential from rainwater exploitation is huge. According to the Beijing Municipal Water Authority, about 230 million cubic metres of rain water can be utilized annually, 110 times the quantity in Kunming Lake, a 220-hectare water body in northwest Beijing. Despite natural collection and the efforts of some 55 pilot rainwater projects, rain water equivalent to around 100 Kunming lakes currently runs off and is wasted each year, stressing the city¡¯s obsolete drainage system and contributing to urban flooding.

¡°Unlike rainwater harvesting in rural areas, urban rainwater utilization isn¡¯t just important for saving water,¡± says Che Wu, a professor with the Beijing Institute of Civil Engineering and Architecture, which has pioneered research in this field since 1998. ¡°It¡¯s also important in abating urban flooding, groundwater depletion, and rainwater runoff pollution, as well as for improving urban ecosystems.¡±

Pilot project

One pilot project, initiated in 2000 by the Beijing Municipal Water Conservancy Bureau and Germany¡¯s Essen University, provides a model for how rainwater harvesting can be used in daily life. Project developers selected five representative sites, including two residential compounds (one recently built and one slated for construction), a section of the old town, urban public construction land, and a school. In these areas, they converted several paved roads into more porous surfaces to encourage rainwater infiltration, and collected and stored rain water from rooftops and road surfaces for use in irrigation, car washing, and toilet flushing.

Although the project has succeeded in saving water and controlling floods, it is not easily replicable, mainly due to the high infrastructure investments required. ¡°It is indeed not very cost-effective to harvest rainwater for direct use in Beijing,¡± explains Che Wu. Heavy rainfall occurs in the city mostly from June to September, a pattern that would render collecting and storage facilities idle for much of the year.

A better alternative, Che believes, is to rely on localised, integrated harvesting, using natural surfaces to promote infiltration for indirect groundwater recharge and exploring ways to harvest rain water for urban waterscaping purposes.

So far, most of Beijing¡¯s rainwater utilization efforts, including the 55 existing pilot projects, have relied on public support. Eight parks are using rainwater for plant irrigation, and several others hope to replicate their experiences. The city is also experimenting with using vegetation to strengthen rainwater purification and infiltration in rivers.

¡°Most of the projects we¡¯ve done are governmental ones,¡± notes Ding Wenduo, General Manager of Beijing Bairun Water-Art Environment Engineering Co., Ltd, which specializes in the design and construction of economical irrigation, waterscaping, and water distribution systems. ¡°The government will remain our major customer in the future.¡±

Building industry ¡¡ Most recently, rainwater utilization has received unexpected enthusiasm from another sector: the real estate industry. ¡°Since the latter half of 2005, we have begun providing consultancy to real estate developers on using rainwater to construct waterscapes,¡± Ding says. He expects this business to grow fairly rapidly in the next three to five years.

Che Wu, with the Beijing Institute of Civil Engineering and Architecture, agrees that ¡°there are huge demands from the real estate industry.¡± Two major factors contribute to this rising interest: water prices and government regulations. Between 1991 and 2004, Beijing raised its residential water prices from RMB 12 cents per ton to 280 cents per ton (US$ 1.5 cents to 35 cents)¡ª a 22-fold increase through nine adjustments ¡ª and there is talk of further increases. A municipal regulation in effect since May 2005 requires residential areas to use rainwater or recycled water, rather than tap water, for waterscaping purposes.

In light of such measures, farsighted real estate developers are investing increasingly in rainwater utilization. ¡°This will save them money in the long run,¡± notes Che. ¡°But most importantly, good waterscapes will add value to their real estate, attracting customers.¡± The interplay of government policies and market forces, experts believe, will provide a continuous push to the city¡¯s rainwater utilization efforts.

Source: China Watch is a joint initiative of the Washington-based Worldwatch Institute and Beijing-based Global Environmental Institute (GEI). China Watch reports on energy, agriculture, population, water, health, and the environment in China.