Study On Ecological Water Level Of Lakes And Its Application

The Ecological Water Level of the lake is an important indicator to measure the health of the lake,and it is also a key factor that determines the stability of the lake ecosystem.Changes in the Ecological Water Level of the lake affect the survivable space within the lake ecosystem,which in turn affects the various types of organisms in the entire lake system.There are many studies on river ecological flow at home and abroad,and relatively few studies on lake Ecological Water Level.This article has conducted in-depth research on the lake's Ecological Water Level from two aspects: the lake's Minimum Ecological Water Level and the lake's Suitable Ecological Water Level.(1)The calculation process,advantages and disadvantages of five methods including annual guarantee rate method,lake morphology analysis method,biological space minimum demand method,natural water level data method and minimum annual average water level method are studied,and the minimum value of Changhu Lake is calculated.The Ecological Water Level is 29.36 m.According to the different inflow conditions,the Minimum Ecological Water Level of the lake was further studied,and the relationship between the Minimum Ecological Water Level of Changhu Lake under different inflow conditions was analyzed.It is found that when the incoming water conditions are different,the Minimum Ecological Water Level value is obviously different.Based on the Minimum Ecological Water Level,the health status of the water level in the historical drought years and recent years of Changhu Lake was evaluated.(2)Research and analysis of the lake's Suitable Ecological Water Level.Analysis of the long-term hydrological data of Changhu,combined with the actual inflow of water in various years of Changhu,calculated the annual Ecological Water Level range of 30.08-32.08 m in the high water year,and 29.86-31.36 m in the year of the normal water year.In the dry year,the lake's Suitable Ecological Water Level range is 29.25m-30.63 m.(3)Using the IHA method,8 indicators reflecting the water level of the lake are proposed to analyze the water level change process of Changhu Lake.It is found that the occurrence of high water level in Changhu Lake is mainly concentrated in June,with a duration of 20-110 days and low water level.The low water level in Changhu Lake is mainly concentrated in April,the duration is 20-150 d,the average water level rise rate is 0.03m/d,and the average water level decline rate is 0.02m/d.