Environmental Engineering Invigorating Polluted Water System
03/23/2016
Kunming waterfall park. Image: Patrick Scally
A new river diversion project is designed to make Dianchi Lake, one of China’s most polluted lakes, “swimmable” again by 2020.
Residents of Yunnan province’s capital Kunming caught their first glimpse of the Kunming Waterfall Park, a 400-metre wide waterfall where farmland once sat, opened to the public on New Year’s Day capping off nearly three years' frantic work. The feat of engineering is a harbinger of drastic environmental solutions being made to the region.
The 1.1 billion yuan (US$168 million) waterfall park is merely the expensive public face of a serious effort to cleanse Kunming’s Dianchi Lake of decades of accumulated pollution that has rendered one of China’s largest fresh water bodies an ecological catastrophe.
One of China’s most polluted lake-Dianchi lake. Image: Emit Chan
Dianchi Lake, once a reliable source of fresh fish for Kunming markets, was seriously polluted during the late 1980s to 1990 with water becoming highly eutrophic (polluted by a high concentration of nitrates and or phosphates), and natural cleansing buffers, such as shoreline wetlands, withered and died.
Local government, under the auspices of the Dianchi Lake Management Authority (DLMA), began a series of costly and unsuccessful attempts to rebalance the lake’s oxygen levels and rid it of algae.
Projects included wetland restoration; planting hundreds of tonnes of invasive water hyacinths; banning all new construction near the lakeshore and injecting ozone directly into the lake. Still, water quality hovered around Category 5, a ranking deemed “unfit for industrial use” by Beijing standards.
Industries with heavy pollution were prohibited along Niulan River area in Yunnan provincial urban planning. Image: xinhua
In 2013, the DLMA began pumping water from the Niulan River towards Kunming. The diversion originates at Deze reservoir in eastern Yunnan, travels west to the northern outskirts of the city and into the Panlong River, which in turn flows through central Kunming before emptying into Dianchi.
The undertaking is part of the 1 billion yuan Waterfall Park project, which now funnels an average of 566 million cubic metres of water into Dianchi each year. The recently opened Kunming Waterfall Park, in addition to being a novel public area, helps oxygenate water headed to the lake.
The results, according to government statistics, have been significant. Dianchi has a natural residence time of roughly four years, meaning anything entering the lake takes an average of four years to circulate through and then exit downstream. That cycle has been sped up to only three years with the addition of the Niulan River water. The accelerated process is credited with lowering levels of organic chemicals such as ammonia and phosphorous resident in Dianchi by 30% over the past two years.
Jinsha River at Tiger Leaping Gorge. Image: chinadialogue
In addition to the Niulan diversion and the installation of modern sewage treatment facilities, even more water will soon supplement existing inflows into the lake. Beginning in June, the Dian Zhong Water Diversion Project will come online. Officially approved by China’s National Development and Reform Commission in January, the undertaking will redirect huge amounts of water from northern Yunnan’s Jinsha River, also known as the headwaters of the Yangtze.
The provincial government has vowed to make Dianchi “swimmable” again by 2020, something no one in the province has witnessed for almost two generations.
