Assessing risks of algal blooms in water transfer based on algal growth potential.

ABSTRACT

Water transfer is an effective way to solve the unequal distribution of water resources to meet the needs of urban residents and industry. Annual wet weight data indicated that there may be algal blooms during water transfer. We explored the ecological risk of water transfer from Xiashan to the Jihongtan reservoir through algae growth potential (AGP) tests. The results showed that the Jihongtan reservoir had certain self-regulation abilities. When the total dissolved phosphorus (TDP) concentration was not more than 0.04 mg/L, the risk of algal bloom was low. When the N/P ratio (by mass) was less than 40, the ecological imbalance of algal growth may be caused. When the N/P ratio was 20, it was the best environment for algal growth. Under the current nutrient condition of the Jihongtan reservoir, the volume of ecological safety threshold in water transfer was 60% of the Jihongtan reservoir's capacity. If the nutrient level was further increased, the water transfer threshold would rise to 75%. In addition, water transfer may cause the homogenization of water quality and accelerate the eutrophication process of reservoirs. Regarding risk assessment, we believe that controlling nitrogen and phosphorus are more consistent with the natural evolution of reservoirs than controlling phosphorus alone for solving the problem of eutrophication.