For years the waters of Dianchi Lake have been fouled by a thick and seemingly intractable algae caused by all manner of pollutants. Several expensive attempts have been made to rectify the situation — ranging from the introduction of an invasive plant species to pumping the lake full of ozone. Earlier this week another financially ambitious effort to save Dianchi went into operation.
The aim of the Dianchi Lake Water Project (滇池补水工程) is fairly simple: divert fresh water from a once unconnected river into the lake and flush it clean. The implementation of such an endeavor, however, proved to be quite complicated. The 8.4 billion yuan (US$1.38 billion) undertaking was completed September 25, following five years of planning and oft-delayed construction.
Water from the Niulan River (牛栏江) will now flow more than 100 kilometers southwest from near Songming before emptying into Kunming's Panlong River and finally reaching Dianchi Lake. On its way the water will pass through three new hydroelectric dams and ten tunnels.
The interconnected series of underground canals and pumping stations make up nearly 90 percent of the diversionary course. Construction of the tunnels was reportedly slowed by a series of cave-ins and flooding that pushed completion back several months.
All told, the project will divert roughly 600 million cubic meters of "clean" water to Kunming annually. In addition to the primary goal of injecting much needed fresh water into the lake, the effort is expected to provide Kunming with another source of water in times of drought as well as generate hydropower.
The source of all this water is the Niulan River, which naturally flows northeast through Zhaotong where it empties into the Jinsha River. An estimated 13 percent of the Niulan's annual flow will now be stored behind Deze reservoir (德泽水库) before being discharged on its way toward Kunming.
The project also included building filtering and aeration facilities along the Panlong River. Many of these utilize natural filtration via plants such as bamboo as well as cascades and man-made waterfalls.
Massive water-replacement endeavours such as the one now underway for Dianchi are not without precedent. Referred to by hydrologists as dilution, the process has successfully been used in cities such as Seattle, albeit on a much smaller scale. How exactly washing away Dianchi's vast supply of algae will affect rivers and people downstream has not yet been discussed in local media.
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