Assessment of eutrophication degree and its prevention in Danjiangkou Reservoir

Nutrient level at Danjiangkou Reservoir was related to the health of water ecosystem and affected the safety of water supply in the middle route of south-to-north water transfer project. Nutrient levels at 15 monitoring sections in Danku and Hanku of Danjiangkou Reservoir were therefore evaluated monthly in 2018 with correlation weighted comprehensive nutrition status index. Further, weight value of nutritional state indexes including permanganate index, total phosphorus, total nitrogen, water transparency and chlorophyll a were compared. Danjiangkou Reservoir was found to be at medium nutrient level in 2018, the average annual comprehensive nutritional status index values were found to range from 31.1 to 37.9, which was higher at Hanku Reservoir than at Danku Reservoir. It was noted that sections of Hanku Reservoir center and Shangenqian of Liubei town were close to light eutrophication level in July and August of 2018. Total nitrogen and chlorophyll a were found to be the most important indexes affecting nutrient level of water body, followed by total phosphorus and water transparency. Permanganate index was found to have little influence on nutrient level of the water body. Nutrient status analysis and assessment were used to provide countermeasures for the prevention and control of eutrophication in Danjiangkou Reservoir: to strengthen management, to construct filtration and purification measures, to do more research on total nitrogen control and algae prevention.