Attribution of lake eutrophication risk to anthropogenic forcing adjacent to the agriculture areas, China

Abstract Lake eutrophication, exacerbated by high-intensity anthropogenic forcing, is a critical environmental problem that threatens water ecological security and the sustainable development of fisheries. Accurate evaluation of lake eutrophication is a prerequisite and basis for effective water environment management. In this study, Chagan Lake, surrounded by agricultural areas with irrigation discharge as the primary water source, was selected as the study area. The weight coefficient of the comprehensive eutrophication index was modified according to the characteristics of the lake. Based on the long-series multi-source data, the spatio-temporal evolution characteristics of the modified weighting coefficient of lake eutrophication and the influence of human factors were analyzed. The results showed that 1) the average eutrophication level of Chagan Lake was eutrophic (TLI=58.31), among which the nutrient level was higher in summer, reaching Hyper eutrophic (TLI=61.49); 2) the eutrophication level in the lake area was influenced by irrigation discharge of the new saline irrigation area, and the trend of eutrophication increased from eastern to western; 3) the maximum pollution footprint affecting the lake reached 34.7 km2 , with a maximum buffer zone radius of 1 km; 4) the GDP of primary industry, total sown area, and rice field area were the main anthropogenic factors leading to the eutrophication of the lake, with contribution rates of 26.41%, 71.34%, and 2.55%, respectively. Multi-dimensional management strategies in terms of maximum pollution footprint, buffer zone radius, and contribution of anthropogenic factors were provided to improve the lake's water quality. All the views can provide scientific support for the water environment management of Chagan Lake and guide the formulation of similar "one lake, one policy" policies.