| Wetlands in the Hei river basin（HRB）and the Bai river basin（BRB）are the main components of the Zoige Wetlands,featuring important water conservation functions in the upstream of the Yellow River.Clarification of wetland dynamics and the storage variation there,as well as the responses of the above to climate change and human activities,might help people better understanding the relationship between wetland ecohydrology and the environmental drivers as for providing scientific support to both the eco-landscape and hydro-function of alpine wetlands.In this study,we collected the gauge-based and remote sensing-based data presenting local topography,meteorology,hydrology,soil type,land use/cover and socio-economy in the two basins.A decision tree was developed to classify wetlands,three of landscape indicators were adopted to characterize the changes of that.The SWAT model was adopted to simulate the lateral water input from the mountainous upstream to the wetland,combined with the remote sensing-based wetland precipitation,evapotranspiration and the measured river discharge at the outlets of the two basins,the hydrologic inputs and outputs of the wetlands were quantified.According to the framework of water balance method,dynamics of wetland water storage（WWS）were obtained,for correlation analysis with the changed wetland landscape.Based on the above,the principal component analysis（PCA）was conducted to comprehensively diagnose the drivings of annual wetlands variations,suggestions were then made for wetland protections in the two river basins.Main conclusions are as follows:（1）Based on the decision tree,three main wetlands in the study area were classified,the spatial distribution of wetland landscape were then illustrated and analyzed.During the statistical period,an overall areal increase of the total wetlands presented,opposite variations in meadow wetlands（MW）and swamp wetlands（SW）were found,showing on the trend that when the one increased,the other one decreased.Specifically,the MW increased while the SW decreased in the HRB,although the situation was inverse in the BRB.（2）The SWAT model was used to simulate the hydrologic processes in the two river basins.Simulation results were fitted with observations from the two hydrologic monitoring stations,variation trends of the simulated and the measured sequence were corresponded well.Regressions resulted into coefficients of Nash efficiency above 0.65and the R~2 above 0.7,meant that simulations based on SWAT could satisfactorily reflect the actual hydrological process,the application of it were suitable in the HRB and the BRB.（3）During the statistical period,the WWS in the HRB generally increased,with a cumulative volume of 3.357 billion m~3.While in the BRB,it was reduced with a cumulative one of 1.187 billion m~3.WWS was found closely related to variations of the large-scale distributed and dominated wetlands,furthermore,the response of WWS to wetland landscape variations presented an effectiveness of delay in time.（4）PCA revealed an interactive driving mechanism of“Socio-economy+grazing+climate”on wetland variations in the two basins.Especially,it was the influence of socio-economic issue dominated the wetland changes at an annual time scale.People need to know restraints of human activities on wetland ecosystems within a reasonable impacting scope is conducive in the water conservation upstream of large rivers,for the sustainability of regional eco-environment and local socio-economy. |
