Zhou Dequn’s post, “Cleaning up Kunming’s Dianchi Lake” discussed the origins of and contributing factors to the lake’s pollution. His post also briefly discussed a few of the measures used to raise the quality of Dianchi’s water in recent years. The marked improvement of Kunming’s groundwater quality was recently profiled in this New York Times video.
PHOTO: Dianchi’s southern shoreline
To clean up the lake, the municipal government used more than a handful of methods over the past fifteen years, but the score card shows mixed results. Some half-baked methods only worsened pollution levels in the lake. The most infamous treatment measure introduced the American water hyacinth, an invasive species, to the lake’s ecosystem in 2005. The water hyacinth’s root system sequesters large amounts of nitrogen and phosphorous pollutants and has a reputation to successfully reduce pollution in freshwater bodies. However, the plant, if not carefully managed, can reproduce at a rapid rate. On Dianchi, the leviathan of the water hyacinth was uncontrollable. Its roots which are are three times longer than its out-of-water stem, provided another problem. The lake’s shallow waters quickly were overpowered. Discarded roots from dead plants filled up the lake bed, exacerbating the eutrophication of the lake and killing nearly every other living organism in the lake.
The lake’s curators, under much ridicule from the conservation world, took years to remove deadly hyacinth from the lake and now have introduced a less damaging purple rooted hyacinth to Dianchi. This plant has a shorter root system and is much less prolific than its cousin. Each November, all purple rooted hyacinths are harvested from the lake, dried at a processing site south of the city, and turned into fertilizer or animal feed – a true win-win, low-cost solution to reducing pollutant levels.
In 2008, a proposal came forward to flush the lake like a toilet bowl by building a 400km long pipe system delivering a replenishing quantity of water from the Jinsha river (upper reaches of the Yangtze) in such a violent fashion that it literally flushes all the lake’s water through its outlet. This high-cost, high-impact method, would require the building of a high dam in the Lijiang/Zhongdian area. Fortunately this proposal was nixed. The potential dam site was located in an active earthquake zone in the middle of the UNESCO protected Three Parallel Rivers zone. The excessive volume of polluted water would have been exported downstream for cities like Chongqing and Shanghai to manage.
Currently, a project is underway to bring water in from the Niulan river, a Jinsha tributary, to Kunming’s drinking water reservoirs, and the added volume will push more water into Dianchi. Should this system go online, where previously it took four years for the lake to replace its water supply, the lake’s water supply will be replaced in only one year.
The method that has worked best in controlling point source pollution and ending the release of public sewage into the lake started with connecting political futures of city officials to the water quality of each of the lakes contributing 36 rivers. Officials will lose their jobs if these rivers are found to be polluted or if they do not act on registered complaints. This innovation led to the construction of a treatment system that separates 100% of the rain water and sewage in the dry season. The separation mechanism surrounds the lake like an iron ring preventing pollutants from entering. However, the system cannot handle the floodwaters of the rainy season and was only recently introduced to the city’s downtown area.
PHOTO: Construction of a downtown sewage separation project on Kunming’s Panlong river, April 2013
Levels of severe ground water pollution continue to worsen in most parts of China. Bordering the provinces of Jiangsu and Zhejiang, the famous Lake Tai is as polluted as Dianchi, and it’s a well-known fact that most groundwater in China’s north ranks at an untreatable Class IV or worse. If improved water quality continues to be seen in Dianchi, perhaps these measures could be implemented in treating other polluted waters in China.
As a homeowner in Kunming, there’s nothing more critical than seeing Dianchi’s water supply become potable. Yunnan province has experienced cycle of dry-season droughts for the past five years. As a result, public water services in many parts of the city, including my housing complex, are often turned off or reduced in an unannounced fashion, making it difficult to provide for basic home amenities like cooking and washing. To help conserve water through the end of this year’s dry season, the municipal government reduced public water output by 150,000 tons and 200,000 tons in March and April respectively.
Kunming, by most accounts, has the most livable climate in comparison to all of China’s other cities with average temperatures of 23 C, clean air (usually), and blue skies, but constant water shortages take down Kunming’s living quality index more than a few notches. In the worst kind of irony, all Kunmingers know China’s sixth largest lake is only a few kilometers from downtown, but its waters are entirely unusable.
Turning Dianchi into Kunming’s core potable water source should be priority number one for decision makers, otherwise, the city’s urbanization push, which will likely double the city’s population, is certain to fail.