Early Warning And Regulation Of Ecological Water Levels Of Rivers In Plain River Network Area

In order to protect river lake ecology,water environment health and sustainable utilization of water resources,it is necessary to carry out research on ecological water demand of rivers and lakes.At present,the research on ecological water demand in China mainly focuses on the basins with obvious seasonal changes and large flow changes in the north,and the research on plain river network areas is still lacking.The plain river network area has dense river networks and rich water resources,but it is greatly affected by human production and life.Due to the needs of social development,the development and utilization of water resources in this area has been continuously improved,resulting in the decline of river water quality,the destruction of aquatic habitats,and the reduction of available water.Considering the river characteristics and water demand in the plain river network area,this paper takes Zongliutang River and Gushan River in Suqian City as the research objects to carry out the river ecological water demand research in the plain river network area.The main research results are as follows:(1)Considering the characteristics and functions of the river,the ecological protection objectives and ecological water level composition are determined respectively.Zongliutang River chooses river connectivity and aquatic habitat as its protection objectives,and its ecological water level consists of basic ecological water level and water level suitable for fish survival;Due to the lack of hydrological data,only aquatic habitat are considered in Gushan River,and its ecological water demand is determined by the suitable water level for fish survival.(2)Considering the basin characteristics and water level characteristics,the Zongliutang River and Gushan River are studied in sections.Considering the stations with existing observation data,and in combination with the First Batch of Ecological Water Levels of Rivers and Lakes in Jiangsu Province(Trial)issued by Jiangsu Provincial Water Resources Department,this study takes Liutang River Sluice and Miaochongxiangjiao Dam as the sectioning points,and divides the total Liutang River into upstream,middle and downstream sections.Calculation and analysis of ecological flow and research on management and control measures for the three sections.(3)According to the characteristics and conditions of rivers in plain river network areas,various ecological water demand calculation methods are compared and analyzed,and suitable methods are selected to calculate the ecological water level.The mean water level of the driest month,dynamic calculation method and RVA method were used to calculate the basic ecological water level;The wetted perimeter method was used to calculate the suitable water level for fish survival.The ecological water level in the upper reaches of the total Liutang River is 17.4m.The ecological water level process in the middle reaches of the year from January to December is 8.95,8.95,8.95,8.97,9.16,9.01,9.13,8.95,8.95,8.98 and 9.02m respectively.The ecological water level in the downstream section is 7.5m.The ecological water level of Gushan River is 12.05m.Tennant evaluation standard is adopted for the rationality evaluation of the ecological water level calculation results of Zongliutang River,and the evaluation results are in the best range.(4)Based on the analysis of the water level situation of Zongliutang River from 2013 to 2020,Mann Kendall trend test shows that the water level of Zongliutang River has an upward trend,and Mann Kendall mutation test shows that the water level of Fulong Station of Zongliutang River has a sudden change in June 2014.By analyzing the influence of precipitation,riverbank vegetation coverage,water conservancy facilities and other factors on river water level in the basin,it is determined that the regulation of water conservancy facilities is the main factor affecting the change of river water level.Precipitation and riparian vegetation coverage also have some influence on water level,but they are not the dominant factors.According to the analysis results of water level influencing factors and the functional division of the two rivers,the maintenance measures for the ecological water level of the river channel are formulated.The ecological water level warning and control system of Zongliutang River and Gushan River has also been established.