Algae Outbreak Threatens City’s Drinking Water Safety

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A large outbreak of blue-green algae last month on eastern China’s Lake Tai—the country’s third largest freshwater lake—has contaminated the main drinking water source of Wuxi, cutting the tap water supply for the city’s 2 million residents for almost three days. While the local government has called the incident a “natural disaster,” triggered mainly by recent high temperatures, little rainfall, and low water levels, experts contend that the major culprit behind the algae bloom is the overload of nutrients in the lake. They suspect that the overgrowth of algae is being stimulated by the input of nitrogen and phosphorus from industrial and agricultural pollution, domestic wastewater discharge, and fish farming along the lake.

The Lake Tai basin, which includes Shanghai and some 34 other cities in Zhejiang and Jiangsu provinces, is the most urbanized and industrialized region of China. It contributes to roughly 11 percent of the national gross domestic product (GDP) each year, while containing less than 0.4 percent of the nation’s total land area. But the region’s “economic miracle” has caused serious environmental and ecological degradation, dramatically increasing the flow of untreated domestic, industrial, and agricultural wastewater into the lake. Overall, the water quality of more than 85 percent of the basin’s main water bodies is deteriorated and not considered suitable for household use.

Although the Chinese government has ploughed large amounts of money into the cleanup of Lake Tai for more than a decade, these efforts have failed to keep pace with pollution driven by rapid economic growth. Meanwhile, the government’s proposed Lake Tai pollution control program has focused mainly on controlling industrial and household pollution sources and has paid less attention to addressing agricultural non-point sources and untreated municipal wastewater, which usually contains high levels of chemical nutrients.

The green-paint look and smelly algae on Lake Tai expands each summer. But this year, it raised alarm among both citizens and government officials about the worsening water quality of the lake. “It is almost like suicide to sacrifice the environment for the economic development,” Yang Weize, the city secretary of Wuxi, commented on the recent drinking water crisis. A local official said a new region-wide management law on Lake Tai is being drafted to reform the organizational structure, define the management mechanism, and clarify the allocation of water sources.

 

China Watch is a joint initiative of the Worldwatch Institute and Beijing-based Global Environmental Institute (GEI) and is supported by the blue moon fund.