Evaluation of aquatic ecological health of sluice-controlled rivers in Huai River Basin (China) using evaluation index system.

The aquatic ecological health status was focused on the Huai River Basin (HRB) from the aspects of water quantity, water quality, water ecology, river connectivity, and riparian habitat environment. Ten monitoring sections were set up in the middle and upper reaches of HRB, and 5 experiments of each section were conducted in July and December from 2012 to 2014. Thus, relevant data on the species, the density of phytoplankton, zooplankton and benthic animals, the concentration of water physicochemical variables, and riparian habitat quality were obtained. Eleven key impact factors were chosen using frequency statistics, theoretical analysis, and correlation analysis methods, forming the evaluation index system of aquatic ecological health. Then, the indicator weight value was determined by the combined weight method, and the health degree was evaluated by the comprehensive index method. On the whole, the aquatic ecological health degree of the upper sections (D1 ~ D3) of the Shaying River ranges from 0.334 to 0.927, which is generally in a "sub-healthy" state. The aquatic ecological health degree of the main section of the Huai River (D8 ~ D10) ranges from 0.362 to 0.777, which is in the "critical" or "sub-healthy" state. The Huaidian Sluice (D5) and Fuyang Sluice (D6) in the middle and lower reaches of the Shaying River had the worst aquatic ecological health. Its water ecological health range is 0.283-0.523, and most of them are under "sub-pathologic." The research results have important theoretical and practical significance. They can enrich the evaluation theories and methods of river aquatic ecological health, help to grasp the aquatic ecological health status in HRB, and provide basic support for aquatic ecological protection and water pollution control in sluice-controlled rivers.