Eco-hydrological Regulations Based On Habitat Requirements Of Grus Leucogeranus

Siberian crane(Grus leucogeranus),the third rare cranes in the world,is identified as the critically endangered species by the Red List.The studies on demand for crane habitat and habitat protection have received special attention at home and abroad currently.Momoge National Natural Wetland Reserve(MNNWR)is an inland wetland and water protection reserves for rare waterfowl as well as great important habitats for Siberian crane.The stopover number of Siberian crane in MNNWR constitutes over 95% of total population every year.Baihe Lake is the main stopover site in MNNWR.In recent years,the water imbalance caused by climate change and unsuitable managements has brought about serious water shortage or extreme water excess,which has exerted detrimental influence on suitable water level needed by Siberian crane and eventually destroyed crane's habitat quality and rest quantity.Therefore,it is necessary to understand how to regulate the water resources efficiently and maintain reasonable hydrological regimes for meeting the demand of crane habitat,so as to provide key information for conversation and reconstruction planning of crane's habitat.In this paper,the relationship between wetland evolution,water area,vegetational cover and the population of Siberian crane in different hydrological year was analyzed by remote sensing interpretation.The quantitative relationship between water depth gradient and growth characteristics of food plants as well as composition and distrubition of the vegetation community also be investigated based on field monitoring and vegetation samples which revealed the demand of crane habitat,reasonable water level and water surface area.The Environmental Fluid Dynamics Code(EFDC)was used to simulate water level change in different pledge probability of precipitation and irrigation return flow scenarios.Finally,eco-hydrological regulations were proposed based on this research.The main conclusions are as followes:(1)Surface water area,vegetation coverage and distribution in Baihe Lake as well as their relationship with crane population was obtained by multi-source remote senses interpretation and statistical data.Results indicated that 2600 ha was the suitable surface water area which corresponding water level was 132.4m.The main habitat types for crane were emergent vegetation zone and soft mud area.The effect analysis of different water depth on food plants growth indicated that the density of Scirpus planiculmis and the height of S.nipponicus under different water depths were the main factors that influenced the population of Siberian crane significantly.The density of Scirpus planiculmis suitable for crane was under the hight of 30-50 cm,because this density can provide a rich food sources and less energy consumption for Siberian crane.Moreover,the height of S.nipponicus under this water depth can also provide a shelter place and wide view for Siberian crane.To sum up,132.4m-132.6m is the suitable ecological water level for Siberian crane.(2)The wetland hydrodynamic model was constructed based on previous section mesh,generalizability of bottom topography,setting of intial conditions and parameters in Baihe Lake.The model was calibrated and validated by the observed water level data and simulated data.The evaluating indicator suggested that the model could simulate the hydrodynamic process in Baihe Lake precisely.(3)The calibrated and validated EFDC was used to simulate variation of water level in different scenarios and proposed corresponding eco-hydrological regulations.The scenarios combined spanning different gradient of different pledge probability of precipitation and irrigation return flow.The variation charactersitics of water level revealed by simulation within different scenarios.The corresponding controlling measures and countermeasures based on the requirements of ecological water level are as follow:In wet year,expand the outflow and drain away excessive water in advance when keep the inflow unaltered.For example,in scenario a,it would expand the outflow which drain away 3.62×107m~3 of water from July to September.In scenario b,it would expand the outflow which drain away 2.14×107m~3 of water from July to September.In normal year,there is no need to regulate only when the precipitation is above normal in September.For example,in scenario c,it would expand the outflow which drain away 2.28×107m~3 of water from September,while in scenario d,there is no need to adjust.In dry year,the inflow is insufficient for meeting the ecological water level Siberian Cranes needed,so it necessitates to feed optimum water supplement.For example,in scenario e,it would expand the inflow which feed 2.92×107m~3 of water and stop water draining from July to September.In scenario f,it would expand the inflow which feed 3.95×107m~3 of water and stop water draining from June to September.