关键词: 库湾水质；富营养化；满蓄期；丹江口水库；南水北调中线工程

Abstract: Reservoir full storage is usually accompanied by processes such as increased inflow pollution load and release from drawdown areas, which have a significant impact on the water quality of reservoirs, especially in bay areas. Based on the monitoring data of eutrophication in 20 typical bays of Danjiangkou Reservoir from 2021 to 2023, the overall spatial and temporal characteristics of bay water quality were analyzed. The nutritional status of typical bays was evaluated using the comprehensive nutritional status index method, and the characteristics and causes of water quality changes in the bays after two full storage periods in autumn 2021 and autumn 2023 were deeply discussed. The results show that: ① The water quality of the bays fluctuated from 2021 to 2023, with the overall nutritional status being mesotrophic. The water quality in the tail areas of the Hanjiang Reservoir and Danjiang Reservoir was relatively poor, and some bays showed eutrophication. ② After the first full storage, the concentrations of dissolved oxygen, total phosphorus, and chlorophyll a in the bays showed a decreasing trend, while total nitrogen, permanganate index, and turbidity increased significantly. After the second full storage, dissolved oxygen and total phosphorus concentrations decreased, while total nitrogen, permanganate index, and chlorophyll a concentrations increased. The nutritional status of the bays remained stable before and after the two full storage periods. ③ The intense rainfall during the autumn flood season had a greater impact on the increase of nitrogen and organic matter in the bays, while the dilution and purification effect after water level rise may have a more obvious effect on phosphorus. The research results can provide a scientific basis for preventing water quality safety risks in the bays during the subsequent high water level operation of Danjiangkou Reservoir.

Key words: bay water quality; eutrophication; full storage period; Danjiangkou Reservoir; South-to-North Water Diversion Middle Route Project