Research On Eco-hydrological Connectivity Evaluation Of Gaoyou Lake Wetland

Wetland is one of the most important environments for humans and animals to survive.It has the functions of regulating climate,purifying the water quality of rivers and lakes,adjusting floods to respond to natural disasters,and protecting ecosystem species diversity.With the rapid socio-economic development and the lack of people's awareness of wetland protection,the ecological environment of the Gaoyou Lake wetland has been destroyed.Unreasonable exploitation and use of shallow bank cofferdams have led to a large reduction in wetland vegetation,and the transpiration of crops has reduced the ability to produce water.As a result,siltation of river beds and reduction of lake water surface,the biodiversity index decreased year by year,and the hydrological connectivity of the Gaoyou Lake wetland weakened,and the ecological function was affected.Based on the concepts and theories of landscape ecology and river ecological restoration in the principles and technologies of ecological water projects,combined with the geography,hydrology and meteorology conditions of the Gaoyou Lake Wetland,this paper selects the indicators for evaluating the hydrological connectivity of the Gaoyou Lake wetland and uses ENVI to interpret the differences.The remote sensing images of the Gaoyou Lake Wetland under different hydrological conditions during the period,the use of Fragstats landscape pattern analysis software to do quantitative research on hydrological connectivity.The conclusions of the study can provide a certain theoretical basis and method for evaluating the degree of restoration of hydrological connectivity in wetlands.The main research contents and conclusions are as follows:Review and summarize domestic and international ecological connectivity assessment indicators,analyze the meaning and scope of each index,combine the Gaoyou Lake wetland profile and the degree of difficulty in obtaining and calculating the indicators,and finally select the connectivity index,plaque cohesion index,and fragmentation index.Quantitative Evaluation of Hydrological Connectivity of Gaoyou Lake Wetland Using Four Indexes of Separation IndexConstruct a comprehensive index of the hydrological connectivity of the Gaoyou Lake wetland,use the range difference method to standardize the index values,use the subjective weighting method to assign weights to the indicators,and finally obtain the connectivity index,plaque cohesion index,fragmentation index,and separation.The degree weights are 0.445,0.283,0.165,and 0.107.Gathering remote sensing images of the Gaoyou Lake Wetland during the periods of 2013 and 2017,supplemented with remote sensing images during the periods of abundance and dryness in 2014 and 2016,and using ENVI remote sensing interpretation models to interpret and classify remote sensing images and use ArcGIS software performed statistical calculations and found that the lake area of the Gaoyou Lake increased by 56.58 km2 in 2017 compared to 2013,and the river area increased by 7.33 km2,and the farmland and rice decreased by 126.21 km2 and 27.2 km2,respectively.During the flood level period,the lake area increased by 150.32 km2 compared with the low water level,and the river area increased by 15.55 km2.Remote sensing image from different periods is inputed to Fragstats landscape pattern analysis software,and calculate the hydrological connectivity index values.It is concluded that the hydrological connectivity is better than the dry water level during the flood level.The increase of water level makes the lake area larger,and the broken patches are connected.Together,the hydrological connectivity is higher than in other periods;the dry water period is due to the reduction of the upstream water,and the water level drops to separate the lakes that were originally connected,and the fragmentation becomes worse,and the hydrological connectivity becomes lower.The hydrological connectivity indicators in the flat water period in 2017 for comprehensiveness and the comprehensive index for hydrological connectivity were higher than those in 2013,and hydrological connectivity became better.