Study On Ecological Water Replenishment Of Naoli River Wetland Group In Sanjiang Plain

The degradation of natural wetlands in China is serious,and water shortage is the key reason for wetland shrinkage.Ecological,agricultural water may conflict,the region’s water resources are insufficient and priority for agriculture.In order to achieve better water supplement effect under the condition of limited water resources,it is necessary to carry out ecological water supplement scheme research based on water supplement effect analysis.In this paper,the wetland water supplement scheme and effect are studied by using the Naoli River wetland group in Sanjiang Plain.Firstly,Firstly,the degradation process of wetland was analyzed by calculating the spatiotemporal change,dynamic degree and land type transition matrix of wetland over the years.Secondly,the ecological water demand of each reserve was calculated,and the characteristics of the water demand process were analyzed.The current situation and strategy of wetland water supplement were discussed.Thirdly,based on Mike21,the hydrodynamic model was constructed and the characteristics of wetland water flow were analyzed.Combined with the characteristics of water flow,water demand and the benefits of water supplement in different periods,the wetland water supplement scheme was optimized.Finally,the effects of different water supplement schemes were compared and analyzed,and the schemes were compared and selected.The land type of wetland after water supplement was predicted by using the FLUS model.The above research is of great significance for wetland water supplement planning and scheme determination.The main research results are as follows:(1)From 1990 to 2017,the area of wetland(swamp and water area)decreased significantly,from 115407 hm~2 in the early stage to 92671 hm~2,and the shrinkage ratio was 19.7%,of which38887 hm~2 swamps were converted into cultivated land during 1990-2000.The cultivated land area in the Naoli River wetland reserve increased from 35176 hm~2 in the early stage to 53818hm~2,with a value-added ratio of 33.6%,mainly distributed in the west and southwest of the wetland and the left bank of Naoli River.(2)The annual ecological water demand of Naoli River,Sanhuanpao,Qixinghe,Dongsheng and Youyi wetland reserve is 430 million m~3,65 million m~3,55 million m~3,77million m~3 and 16 million m~3 respectively,and the total water demand is 643 million m~3.The ecological water demand process of each wetland reserve is calculated,and the characteristics of"M-type"process of wetland water demand is analyzed.According to the law of wetland water demand process,the contradiction between supply and demand of water resources in the study area,and the benefits of water supplement in different times and periods,three wetland water supplement schemes are optimized and designed:centralized water supplement scheme in April(scheme 1),water supplement scheme on demand from April to October(scheme 2),water supplement scheme by stages in April and July(scheme 3).(3)Through the comparison of different water supplement schemes of Naoli River wetland and Sanhuanpao wetland,the simulated water supplement effect of the staged water supplement scheme in April and July is the best.In the case of water supplement scheme 3,the maximum water supplement areas of Naoli River wetland group and Sanhuanpao wetland are 1703.1 km~2and 215.3 km~2 respectively,and the average water area of the whole water supplement process is the largest,which is closer to the recovery goal,followed by scheme 1 and scheme 2.In scheme 2,the flow time of water replenishment on demand is long,and the process of water demand and water replenishment is not synchronous.In scheme 1 and 3,the water demand of wetland can be replenished to the water demand area in time,which can overcome the lag of water flow.But in scheme 1,the centralized water replenishment will cause inundation to the surrounding irrigation area,and there are many areas with low and high water depth,and the spatial and temporal distribution of different water depth is uneven.The water supply process in April and July is more in line with the characteristics of"M-type"water demand process.With this scheme,the change process of water depth can better meet the living conditions of organisms and create a suitable habitat environment.(4)According to the prediction of land type of Naoli River wetland in 2030 after water replenishment:the swamp and water area will increase by 0.6%and 16.8%;With the implementation of the cultivated land change wetland plan,the area of cultivated land will be reduced by 2.1%;The woodland area is basically in a stable state.The area of cultivated land decrease and wetland increase is mainly reflected in the eastern riverside and central region of Naoli River wetland.Wetland ecological water supply project will play a good role in wetland ecological restoration and evolution.