Predicting The Impact Of The Water Transfer Project From Yangtze River To Huai River On Habitats Of Wintering Waterbirds In Caizi Lake Using Remote Sensed Images

Caizi Lake is an important part of the wetland complex along the Yangtze River,providing wintering area and stopover habitats for "East Asia-West Australasia"migratory waterbirds.Various wetland patches are exposed in Caizi Lake,such as grassland,mud and shallow water area,offering a variety of habitats for the overwinter waterbirds,after the water level recedes in autumn and winter.At the end of September,wintering water birds migrate to the Caizi Lake,and their number reaches maximum in November.Wintering water level of Caizi Lake will change significantly;after the implementation of the water transfer project,named Leading water from Yangtze to Huaihe River,leading to the change of wetland landscape pattern,which has an important influence on and the wetland biodiversity,especially the influence on wintering waterfowl habitat should arouse more attention.Our research is based on the data of remote sensing image,dynamic water level and survey of overwintering water birds,combined with supervised classification(maximum likelihood)and artificial visual interpretation;to explore the distribution and area change of waterfowl's habitat at different water level in Caizi Lake;and find the relationship between water level and habitat area,so as to predict the effect on the habitats of the wintering waterfowl after the water level rise.Our research also proposes some advice to moderate the effects after the implementation of the project.In 2016 and 2017,two field survey recorded a total of 42 species of waterbirds,belonging to 6 orders,12 families,including 21 species of wading birds with 16669 body,18 species of swimming birds with 17225 body,3 geese with 15556 body.The proportion of wintering waterbirds in Caizi Lake is 78.6%(33 species).The largest 6 species of wintering waterfowl population are:Bean goose(Anas.fabalis),Spot-billed Duck(A.poecilorhyncha),White Spoonbill(Platalea leucorodia),Mallard(A.platyrhynchos),Great Cormorant(Phalacrocorax carbo)and Gray Heron(Ardea cinerea),which accounts for 72.4%of total numbers.The water level and wetland landscape pattern of Caizi Lake have obvious seasonal changes,wet season is higher(The average water level is 12.89 meter from 2007 to 2016).After the end of October,a large number of grassland and mudflats exposed for wintering waterfowl foraging with the water level fall.The area of mud and grassland both decline with the water level arises,the area of grassland and mud do little change when the water level is higher than 11.5 and 13.1 meter respectively.Waterbirds of 7 surveyed points will be heavily affected after the implement of the project.We suggest that these 7 areas should be protected as the key areas of wintering waterfowl.Our research indicates that;the fluctuation of water level is one of the main factors leading to changes of the landscape pattern in the Caizi lake,resulting in greater impact on the wintering waterfowl habitat,and an adverse effect on waterfowl wintering in Caizi Lake which has adapted to this seasonal trend.In this research,the water level of maximum area change rate of grassland and mud are 11.5 and 13.1 meter respectively,but 13.1 meter is higher than the average water level in wet season,thus,we choose 11.5 meter as the maximum water level after the implement of the project.Based on above results,in order to guarantee sufficient habitats for wintering waterbirds in Caizi Lake,we suggest that the water level of wintering should not exceed 11.5 meter.