Shedikeng Reservoir, Nanping Reservoir and Zhuxiandong Reservoir are three series of reservoirs that supply water to Macao in Zhuhai, with an average daily supply of 2.2×10.5m3 to water plants in Macao and Gongbei. However, it is difficult to meet the water demand of the reservoir itself. Pumping water from Modaomen Waterway of Guangchang Heping Port Pumping Station enters Nanping Reservoir and then Zhuxiandong Reservoir, or pumping water from Hongwan Waterway of Hongwan Pumping Station first enters Shedikeng Reservoir and then enters Zhuxiandong Reservoir. When the water supply of Zhuxiandong Reservoir is insufficient, the water intake point of Hongwan Pumping Station is located in the downstream of Modaomen Waterway, and the water quality is poor. Long-term water supply to the reservoir has increased the nutritional load of the reservoir. The water transfer of Shedikeng Reservoir mainly occurs in June, 5438+ 10 and March, and the hydraulic retention time is long. Nanping and Zhuxiandong reservoirs have frequent water transfers and short hydraulic retention time, with an average of 23.5 days and 10 days. In 2006, the eutrophication and phytoplankton in three reservoirs were investigated. It was found that cyanobacteria bloomed in Shedikeng reservoir with low nutrient concentration in April, while the biomass of cyanobacteria in Nanping and Zhuxiandong reservoirs with high nutrient concentration was very low. The former is mainly diatoms, while the latter is mainly green algae. What causes the difference of phytoplankton community structure in these three reservoirs? The phytoplankton in Shedikeng Reservoir are mainly Microcystis, Anabaena, Cyanobacteria, Chlorella and Cyclotella. Anabaena is the dominant species of phytoplankton in Nanping Reservoir. , Microcystis. Synechococcus. And microalgae. ; The dominant species of phytoplankton in Zhuxiandong Reservoir is Chlamydomonas. , Microcystis. Comparing the three reservoirs, in April, Shedikeng Reservoir was dominated by cyanobacteria, followed by green algae, and in June, 5438+February, it was dominated by diatoms. In April, the dominant group of Nanping Reservoir was green algae, followed by diatoms in the next three months, cyanobacteria in June and August, and Chlorella in June and February. The phytoplankton abundance in Zhuxiandong Reservoir is the highest in April, and the dominant species in this period is Tetraflagellates of Chlorophyta. In June, the dominant phytoplankton species in Zhuxiandong Reservoir were similar to those in April, but the biomass decreased obviously. After three sampling, the dominant species changed frequently, and diatom, green algae, cyanobacteria and euglena became the dominant species successively. Canonical correspondence analysis (CCA) was used to analyze the relationship between phytoplankton and environmental factors in three reservoirs: pH value, water level storage capacity, phosphorus and hydraulic retention time were the most direct relationships with phytoplankton distribution; Transparency and rainfall also have some influence. In Shedikeng Reservoir, the concentrations of total phosphorus and orthophosphate are the main factors affecting the abundance of cyanobacteria, while diatoms are related to storage capacity and transparency. In Nanping Reservoir, the hydraulic retention time of diatoms is short,,,,

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