东莞市25座水库的营养现状与水质管理对策

为了解东莞市水库富营养化现状并为水质管理提出合理建议,于2011-2012年的丰水期、平水期和枯水期,对东莞市25座水库的营养状态和浮游植物主要参数进行分析。结果显示,中营养水库5座,富营养水库16座,超富营养水库4座,整体富营养化水平较高。水库浮游植物丰度1.07×105~7.67×108个/L,且枯水期高于丰水期;有20座水库的浮游植物丰度中蓝藻比例超过50%,部分水库出现了蓝藻水华现象,其营养状态与人类活动强度、流域内土地利用类型、水库功能及补水方式密切相关。削减外源污染,尤其是控制磷排放是当前遏制水库富营养化的根本途径;对于即将联网调水的5座水库而言,利用联网形成的调度能力进行合理的水库调度是缓解其富营养化的可行措施。

Eutrophication and Water Quality Management of Reservoirs in Dongguan City

Dongguan City in Guangdong Province, located on the Dongjiang River downstream of the Pearl River Delta, has more than 118 reservoirs with a water capacity of 4.07×108m3, but the actual water supply of these reservoirs only accounts for 50% of the total water supply volume due to the limitation of water quality. In this study the eutrophic status of the main drinking water supply reservoirs in Dongguan City were investigated to determine the causes of eutrophication and cyanobacteria blooms in the reservoirs, and provide insights to improve management of water quality. The trophic state, phytoplankton abundance and biomass of 25 reservoirs in Dongguan City were determined and analyzed in wet, normal and dry seasons from 2011 to 2012. The concentrations of total nitrogen and total phosphorus were determined using national standard methods and the concentration of chlorophyll a was evaluated by the acetone extraction method. The results show that five reservoirs were mesotrophic, sixteen were eutrophic, and four were hypereutrophic. The abundance of phytoplankton ranged from 1.07×105 cell/L to 7.67×108 cell/L and was higher in the dry season than in the wet season. Cyanobacteria accounted for over half of the total phytoplankton population for 20 of the 25 reservoirs and cyanobacterial blooms occurred in a few reservoirs during dry season. The trophic status of these reservoirs was significantly related to the intensity of anthropogenic disturbance, land use in the catchment area, function of the reservoirs and water replenishment method. Strengthening the supervision and control of external pollution, especially reducing the total loads of phosphorus to the reservoirs, is the effective and ultimate measure for controlling eutrophication in the reservoirs. Proper reservoir operation can alleviate eutrophication of the five reservoirs connected by the Dongjiang River and Reservoir Water Network Project in the near future.