Study On Ecological Water Level And Water Storage Characteristic Curve Of Baiyangdian Lake

Baiyangdian ecosystem is the most important wetland ecosystem in North China.The main factors affecting the stability of the system are water level and corresponding water storage capacity.The natural water inflow in the upper reaches of Baiyangdian Lake has been greatly reduced since 1980s,which needs to be maintained by ecological water supplement.Considering the higher requirements of xiong’an New Area on the ecological environment of Baiyangdian Lake,the appropriate ecological water level and corresponding water storage capacity are determined from the aspects of hydrology,topography and ecological conditions.The water level storage capacity curve of Baiyangdian Lake is the key to determine these factors.Since the traditional water storage characteristic curve was drawn in the 1970s,the topography and surface features in the lake have changed greatly in recent decades.On the basis of field measurement,the determination of new storage characteristic curve is of great significance to the water level and water quantity control of Baiyangdian Lake.The main contents and conclusions of this paper are as follows(1)According to the requirements of xiongan New Area Construction for Baiyangdian,Baiyangdian has been surveyed with national 85 elevation datum since 2018.On this basis,a 1:2000 topographic map of Baiyangdian Lake is formed,and the distribution of typical features such as villages,reed fields,embankments and cofferdams is understood,and the digital elevation model of Baiyangdian Lake is generated,which lays the foundation for the determination of ecological water level and the drawing of characteristic curve.(2)Through the analysis of the characteristics of natural water level change in Baiyangdian from 1920 to 2016,the change trend is obtained.Based on the results of sliding t test and m-k test,the water level variation point is determined as 1965.After excluding the abrupt water level,the high-frequency water level ranges of the average monthly flood season(July to September)and non flood season(10 to June of the next year)are sorted out,and the ecological suitable water level range of Baiyangdian Lake is determined as 6.4-7m.Through the analysis of water depth distribution map and submergence area map under different ecological water levels in Baiyangdian Lake,the ecological state under 6.4～7m water level is the best,which verifies the rationality of this water level range.(3)Based on the digital elevation model of Baiyangdian Lake,the inundation area and storage capacity of Baiyangdian Lake under different water levels were calculated by using the surface volume tool of ArcGIS and for iterator.On the basis of accurate calculation,a new curve of water level inundation area storage capacity is formed.Compared with the traditional curve,the overall trend of the two curves is the same.When the storage capacity of Baiyangdian Lake calculated in this paper is only around the water level of 7.5 m,the value of the original curve is lower than that of the original curve,and other water levels are higher than the value of the original curve.Finally,in order to maintain the ecological suitable water level range of Baiyangdian Lake,the net water demand curves of different water levels are made,which provides basic data for water resources regulation and control of Baiyangdian Lake.