Study On Ecological Water Requirement In Freezing Period Of Songhua River

Under the dual effects of climate change and human activities,the ecosytem in the north alpine region of China has been seriously impacted.,The extreme weather is frequent,the river flow is decreasing and the water quality is worsening.In 2013,the proportion of bad V river is 14.9% rose 0.6 percentage points than 2012.Currently in the changing environment.,the water ecological problems have become more and more intense,especially in the north river,the ice period up to five months,had a profound impact over the river ecosystem.From 1980 to 2000,due to less rainfall in the region,excessive use of water resources and unreasonable development.There are two rivers interrupted in the Songhua River area,respectively,Hulan River and Ants River,with the maximum length of 50 km and 65 km,0.6% and 2.9% of the total length of the river,and 78 days and 23 days respectively.However,the river ecosystem has a great impact on the ecological environment and its diversity.Under this background,the water ecology gradually becomes the hotspot and difficult area to regulate water and scientific research in our country.However,it is still in the exploratory stage to evaluate the application of the ecological water demand based on the habitat of aquatic organisms in the study of ecological water demand in China since the 1980 s.Especially during the ice period,all the rivers are frozen,and some rivers often appear as "freeze" phenomenon.The existing ecological water demand calculation methods have certain limitations,it is more difficult to adapt the ecological water demand calculation to the cold river in the north.Therefore,it is very important to study the ecological water demand in the alpine region during the glacial period,which is of great significance to the river ecological restoration and management.This paper based on the characteristics of the ice age and the physical habitat model in the Songhua River,the ecological flow in the river channel is forecasted and analyzed from the viewpoint of maintaining the survival of the typical species in the river course during the overwintering period.The main conclusions of this paper is as follows:(1)The hydrological elements of Songhua River during 1962 to 2010 were analyzed,the results shown that:the average annual flow of the Songhua River in Harbin,Yilan and Jiamusi showed a decreasing trend,with the tendency rates of-1.816m3 / s,-0.2419m3 / s,-3.539m3 / s respectively;The tendency of ice thickness are-0.0329 m,-0.0311 m,-0.0325 m,respectively,the flow rate is also showed a decreasing trend,but the tendency of decrease is not obvious.The variation of the thickness of the ice sheet with the accumulated temperature,flow rate and flow velocity can be well fitted by the multivariate nonlinear regression model,and good correlativity is obtained under the Nash coefficient test.(2)To determine the main wintering field distribution of different fish species in Songhua River.Based on the PHABSIM model,the distribution and variation of wintering habitat of two fish species under different flow conditions were simulated by using the warm water-based Leuciscus sylvestris and the cold-watered Aaohua as an indicator species,and the main wintering field distribution of Aohua and Leuciscus from Harbin to Jiamusi section are the areas of 50-70 km,270-280 km and 390-400 km from the Harbin section.(3)Based on the relevant parameters,the relationship curve of WUA-flow rate was obtained,and the ecological flow was determined according to the change in habitat area under the different flow rates of wintering habitat of Aohua and Leuciscus.range.Based on the analysis of monthly runoff data in Harbin,Yilan and Jiamusi stations from November 1962 to March of the following year,considering the actual situation of wintering runoff,the minimum ecological flow of Aohua was 300m3 / S,and the minimum ecological flow rate was 200m3/s during the wintering period.