Trophic States and Nutrient Output of Tributaries Bay in Three Gorges Reservoir After Impoundment
三峡水库成库后支流库湾营养状态及营养盐输出

After the Three Gorges Reservoir was storage water in June 2003, total phosphorus (TP), total nitrogen (TN), chlorophyll a (Chla), Potassium Permanganate Index and Secchi depth (SD) were determined in 12 tributaries bay in Three Gorges Reservoir. Trophic states were assessed and output fluxes of TN, TP and Potassium Permanganate Index were calculated. The results showed that value of TN,TP, Potassium Permanganate Index, SD and Chla were different in each tributary bay. SD,TN,TP, Potassium Permanganate Index and Chla value are 0.10~3.5m, 0.535~7.47mg?L-1, 0.016~0.835mg?L-1, 1.55~5.88mg?L-1 and 1.38~23.7mg?m-3 respectively. The water body of tributaries is polluted at various levels. The concentration of TN is abundant. The rate of TN and TP showed that a part of tributaries eutrophication are limited by TP. The correlation of nutrient and Chla were researched. It indicated there was a significant positive correlation(r=0.6242) between chlorophyll a and Potassium Permanganate Index. Utilizing the method of integrated nutrition state index, it assessed the trophic states degree of tributaries bay. The integrated nutrition state index ranged from 33.3~66.1. All of the studied tributaries, 5 tributaries are eutropher in May and 8 tributaries are eutropher in June. The rest of tributaries are mesotropher. The degree of eutrophication is more serious than before the Three Gorges Reservoir impoundment. The nutrient fluxes load was calculated by discharge and concentration of each tributary. The nutrient fluxes load of TN,TP, Potassium Permanganate Index and NH3-N are 668,26.7, 890and 99.2g?s-1 respectively. After the Three Gorges Dam was completed in 2009, eutrophication trend of tributaries estuaries will be more serious with the more slow flow velocity.