Characteristics of water purification pattern of Caofeidian freshwater reservoir

Caofeidian freshwater reservoir is nearly to the lower reaches of Shuanglong River area, which is located on the coast of Bohai Sea. However, the two sides of the Shuanglong River are the agricultural production and cultivation and aquaculture areas, that resulting in serious agricultural non-point source pollution. In this paper, we introduce a water purification pattern of freshwater reservoir based on floodplain wetland and ecological ditch. We set up floodplain wetlands to purify water with Shuanglong River floodplain and the reservoir surrounding idle beach, and lay out ecological ditch to purify rice paddy fields drainage with rice paddy ditch. Calculated, the water purification system of floodplain wetland could reduce the storage of pollutants, including 450 tons of COD, 18 tons of total nitrogen, 3.6 tons of total phosphorus annually, and reduce the water evaporation of 14,000 m 3 annually. Paddy field ecological ditch strengthen the water purification pattern, can effectively remove the storage of pollutants with 4 tons of total nitrogen, 0.8 tons of total phosphorus annually, and conserve 1,000 m 3 water nearly. It could improve the water quality of the storage river by the water purification pattern of Caofeidian freshwater reservoir, which also has environmental and economic benefits and provide inspiration for the construction of similar freshwater reservoirs.