The impact of climate change has deteriorated water quality at reservoirs. An Environmental Protection Agency (EPA) environmental water quality monitoring report for last year showed, 40 percent of the nation’s major reservoirs are having eutrophication problems.
An academic said it is difficult to address the climate change problem quickly, but the government can improve the management of the upstream catchment areas, while an environmental protection group has urged the EPA and the Water Resources Agency (WRA) to set up management rules for catchment areas.
EPA Department of Water Quality Protection Director Yen Hsu-ming (顏旭明) yesterday said eutrophication occurs when nutrients, mainly nitrogen and phosphorus, are overabundant in a water body leading to an excessive algal growth, an exhaustion of dissolved oxygen levels, and the death of fishes and other aquatic creatures.
Photo courtesy of the Northern Region Water Resources Office
The EPA environmental water quality monitoring report last year showed that of the 20 major reservoirs in the nation, the water quality of eight were eutrophic, including the reservoirs of Sinshan (新山水庫) in Keelung, Shihmen (石門水庫) in Taoyuan, Baoshan (寶山水庫) in Hsinchu, Mingde (明德水庫) and Liyutan (鯉魚潭水庫) in Miaoli, Baihe (白河水庫) in Tainan, and the Chengching Lake (澄清湖水庫) and Fengshan Reservoirs (鳳山水庫) in Kaohsiung.
The water quality of 11 major reservoirs were considered mesotrophic, meaning they contain medium levels of dissolved nutrients, and only New Taipei City’s Feitsui Reservoir (翡翠水庫) had the best water quality, considered oligotrophic, meaning having low levels of dissolved nutrients.
The water quality at all 26 reservoirs in the outlying islands was eutrophic.
Historical data show that the percentage of eutrophic reservoirs on Taiwan proper increased from 25 percent in 2007, to 35 percent in 2015, and 40 percent in 2021, because of a nationwide drought, but even despite last year’s abundant rainfall, eight major reservoirs still had a eutrophication problem.
In addition to livestock wastewater affecting the reservoir water quality, Lifetime Distinguished Professor Chen Shu-chin (陳樹群) at National Chung Hsing University Department of Soil and Water Conservation said temperature and water residence time also significantly affect eutrophication.
As climate change has been leading to more droughts in the past few years, the lack of rainfall has caused water to stay in the reservoir for longer, so when temperatures rise, eutrophication might occur easily, he said, adding that the reduced number of typhons in the past few years might also have contributed to the eutrophic reservoirs.
“To solve the reservoir sedimentation problem, it is crucial to manage the upstream catchment areas,” Chen said, giving the example of Taichung’s Deji Reservoir (德基水庫), which used to have bad water quality due to hillside road construction and the fruit grown in its upstream catchment area, but whose the water quality significantly improved after the Forestry Bureau reclaimed the overused state-owned forest land.
He said the Feitsui Reservoir always has the best water quality in the nation because the catchment area was designated as the Taipei Water Source Domain, prohibiting all development activities in the area.
Taiwan Water Resources Protection Union director Jennifer Nien (粘麗玉) said deforestation and road construction in the upstream catchment areas would lead to increased sediment accumulation in the reservoir, reducing the water storage, increasing the water turbidity and deteriorating the water quality.
“If the EPA only monitors the statistics, it does not substantially improve the water quality,” she said, urging the EPA and the WRA to set up management rules for the upstream catchment areas.
Yen said bad water quality increases the cost of water treatment, as more chlorine or activated carbon would be needed, but the EPA routinely tests the water quality after treatment to ensure it meets the drinking water quality standard, while the Taiwan Water Corporation also tests the water quality before supplying water, and that the pass rate has always been above 99.7 percent.
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