Analysis And Effect Evaluation Of The Yongding River(Beijing Section)Ecosystem Restoration

Yongding River is the largest branch inside the Haihe River basin and it flows through Hebei Province,Beijing,Tianjing into the Bohai Sea.It is consisted of two upstream which are Sangan River coming from Shanxi Province and Yan River coming from Neimeng Province.The daily management of Yongding River in the past was focused on the flood defense,but after the Guanting Dam built in 1954,the flood situation has been controlled.The average precipitation in Yongding River basin is 360~650mm,and the average annual runoff is 20.29 billion m~3.Since 1980 s,due to the years of drought,the lower reach of Yongding River basin plain cannot get enough water supplies,which cause the river dried-up,the aquatic biological extinction and the water ecological environment degradation.《Beijing Yongding River Green ecological corridor construction plan》has been approved in 2009.The first batch of projects was completed in 2012,which means the Yongding River environment recovery project has achieved its first accomplishment.Carrying on the research of ecological restoration and ecological water requirement is benefit for gathering and extending experience of ecological restoration through the whole Yongding River Basin,and improving the Jing-Jin-JI region environment.The essential problem for Yongding River environment recovery project is to find a stable supply of water,which has to ensure the Yongding River can maintain a ecological base flow,and the water quality reaches a certain standard.The ecological water requirement for the river basin should consider the ecological runoff,the water requirement for static lakes,the water for aquatic animals,plants and wetland vegetation living.Hydrology and hydraulic are the two majority methods to calculate ecological water requirement across the world.Hydrology method uses long term observation data to simulate the recommend ecological water requirement.Hydraulic method builds equations between flow discharge and other hydraulic variables.Using the hydrology method,the minimum ecological water requirement for Yongding River Guanting Gorge is 92.6 million m~3 ?a and the idea ecological water requirement is 429 million m~3 ?a.Using the hydraulic wetted perimeter method,the ecological discharge is 13.69 m~3 ?s and the ecological water requirement is 423 million m~3 ?a.Using the hydraulic radius method,the ecological discharge is 12.43 m~3 ?s and the ecological water requirement is 392 million m~3 ?a.The river bed for Yongding River basin plain section mainly contains four kinds of landscape which are sand pit,forest land,dry land and golf course.The landscape of the river bed was developed under a certain historical condition,which breaks the continuity of Yongding River flow channel.The ecological water requirement for the Yongding River basin plain section should meet the need of water surface evaporation,soil erosion,vegetation irrigation,consumption and evaporation.The actual water distribution for Yongding River city downtown section(18.4km long,385 hm~2 area,402 hm~2 green space)is 11.24 million m~3 ?a.Using the nutritional scoring method and comprehensive nutrition state index method to evaluate the water quality in the Yongding River basin plain section,the water quality was in the state of eutrophication.Therefore,the water quality can be improved.Ecological restoration of Yongding river have greatly improved it’s ecosystem services value.Currently,the security degree of Yongding River ecological water requirement is low.The State Council and the local water administration departments have proposed a variety of ways to ensure the ecological water requirement for Yongding River.Considering all the proposals,Wanjiazhai Yellow River diversion is the optimization scheme.Water can follow from the upstream to the downstream and secure ecological use of water for the whole river basin.The ecosystem restoration for Yongding River Beijing downtown section is only focus on ecological water requirement.Lacking of consider the whole river basin ecological system through upstream to downstream,river bank to river channel,also doesn’t think about using the comprehensive assessment to evaluate the whole river basin ecosystem restoration situation.In addition,to achieve ecological restoration for the whole river basin in a systematic and whole society participates way,studying and formulating ecological compensation policy is one thing should be done.