The role of wetland in water quality purification and maintenance of coastal reservoirs: a case of Qingcaosha Reservoir

Abstract

Qingcaosha Reservoir (QR) is typical fresh water storage and salty water avoidance featured coastal reservoir, which is located in south branch of Yangtze River Estuary, China. Due to the location of QR, pollutants and short-term salt tides have threatened the clean fresh water intake of the reservoir. There are 289 km² shoal wetlands in upstream of QR. After the continuous purification of wetlands, water quality of raw water has been improved. Qingcaosha shoal, Zhongyangsha shoal, Beixiaohong shoal and Dongbeixiaohong shoal are on the circumference. From the water quality monitoring data after the reservoir operation, the average value of NH₄⁺-N, NO₃^--N, TN, TP in the outlet are 81%, 65%, 77% and 66% of the inlet respectively after flowing through the natural wetland in the reservoir. The wetlands can solve two major problems facing the coastal zone reservoirs that enhance intake water quality and stabilize water quality. In the design of coastal reservoirs, we suggest that we should make the full use of existing wetlands, enhance the function of wetland water purification through ecological engineering methods, and construct artificial wetlands as a supplement.