Eutrophication trend analysis and forewarning model construction of water source reservoirs: Gaozhou Reservoir, China

The eutrophication of water in reservoirs and lakes is worsening year after year and has become a prominent issue of environmental water protection. In order to understand the degree of eutrophication and the changing trend of important drinking water sources in the coastal areas of Western Guangdong, ensuring the safety of drinking water, this paper takes Gaozhou Reservoir as the research object. According to the long-term monitoring results of eutrophication index of reservoirs from 2012 to 2019, spatial and temporal analysis of each evaluation indicator and the comprehensive nutrient status of the reservoir was conducted using the integrated nutrient status index method. Based on the Weber-Fechner (W-F) law, an early warning model for reservoir eutrophication and grading evaluation was established. The results showed that Gaozhou Reservoir was in mesotrophic state, and the eutrophication was more serious in the high water period than in the low water period. TLI (TN) was the largest contributor to eutrophication of the reservoir, and all nutritional status indexes show mild eutrophication. Chl-a, phosphorus nutrients and organic matter had little effect on the degree of eutrophication. The fluctuation of the eutrophication status at each monitoring section of the reservoir was relatively stable. The TLI(sigma) of Liangde Dam was lower than that of the Shigu Reservoir, and the comprehensive nutritional status of the Shigu area in the decreasing order was tail > supply port > centre. According to the established early warning model, the eutrophication status in different seasons from 2012 to 2019 was evaluated. The results indicated that the comprehensive influence index value of the dry period was less than that of the flood period due to the influence of seasonal factors. In addition, the model has a good warning effect; it provides theoretical support and prevention and control methods for ecological environmental protection of reservoirs.