Socio-hydrologic Analysis And Modelling In Wuding River Basin Based On The Coupled Water And Energy Balance Hypothesis

In recent years,significant changes have taken place in the Earth's climate system.Under the changing environment consisting of changing climate conditions and increasing human activities,the hydrological cycle in the basin has gradually evolved from a natural hydrological cycle into a "socio-hydrologic" cycle.The relationship between hydrology and society is more than a simple exchange of water due to increasingly frequent human activities.Traditional hydrological analysis or simulation research methods,which treats the hydrology and society as two separate systems,have faced challenges.The accuracy of the analysis and simulation results obtained by the method that treat human activities as an exogenous variable in the hydrological system has been questioned.Since the 1970 s,Large-scale water and soil conservation and ecological restoration work in Wuding River Basin coupled with climate change have severely affected the hydrological cycle in the basin.For these phenomena and problems,this study intends to consider society and hydrology as a system under the framework of socio-hydrology;this study intends to do socio-hydrologic analysis and modelling in Wuding River Basin based on a system which contains hydrology and society.In this study,a socio-hydrologic analysis system is established based on the Budyko hypothesis as well as the recession-curve-displacement method and item-by-item investigation.And we identify and quantitatively analyze the interannual changes in groundwater storage,evapotranspiration,and runoff in the Wudinghe River Basin between 1975 and 2010 through the socio-hydrologic analysis system.At the same time,a socio-hydrologic model is established based on the water balance formula and the physical drive mechanism among climate,society,and hydrology factors.The socio-hydrologic model can be used to simulate the social and hydrological changes in the Wuding River Basin in order to provide technical support for water resources management decision-making in the basin.The specific research content and conclusions in this study are as follows:(1)The climate conditions,land-use types,and social factors of the Wuding River Basin have undergone complex changes from 1975 to 2010.These changes,which constituted a complex changing environment in the Wuding River Basin,have influenced the hydrological cycle of the river basin in different directions.Under this changing environment,the characteristics of the hydrological cycle in the Wuding River Basin should be uncovered from the perspective of socio-hydrology.From 1975 to 2010,the reduction of precipitation directly led to a decrease in water input to the basin;increased air temperature,reduced air pressure,and decreased relative humidity led to an increase in evapotranspiration in the river basin,resulting in a reduction in runoff;decreased wind speed and sunshine time will cause the decrease of evapotranspiration in the river basin,which led to an increase in runoff.The significant increase in population,agricultural irrigation area,livestock number,industrial output value,reservoir number,and warping dam number indicate that water intake activities led to an increase of the water circulating in society.Changes in the condition of the underlying surface in the river basin caused by human led to a changed mechanism of runoff yield and concentration which caused a significant reduction in runoff in the basin.Different changes of driving factors led to high complexity of the changing environment in Wudinghe River Basin.The study of the hydrological cycle in the Wuding River Basin should be conducted under the framework of socio-hydrology.(2)Under the framework of socio-hydrology,a socio-hydrologic analysis system and a socio-hydrologic model are established based on the Budyko hypothesis.(1)The socio-hydrologic analysis system has achieved a quantitative attribution analysis of evapotranspiration and runoff changes at the annual scale through water balance formula in basin,calculation of groundwater storage variation in basin and the Budyko hypothesis.(2)Compared with existing studies,the socio-hydrologic analysis system has improved on the time scale of research.The quantitative attribution analysis of groundwater storage at the annual scale can be realized according to the base flow,groundwater recharge,and groundwater exploitation.The quantitative attribution analysis of evapotranspiration and runoff at annual scale can be realized according to climate change,human water use activities and changes in underlying surface.These analyses provide means and basis for further research on water resources management in basin.(3)The socio-hydrologic model,which bases on the socio-hydrologic analysis system,achieves the quantitative description of the physical relationships among different factors.Based on the model,the future change of surface water and groundwater resources in basin can be simulated and analyzed by setting social water intake and underlying surface conditions.(4)Compared with the traditional hydrological model,the socio-hydrologic model achieves the hydrological simulation under the complicated changing environment.The model has the advantages of strong physical model structure,simple parameters,easy access to input data,including human activities,and the ability to simulate simultaneous changes in an environment that climate and human activity conditions change simultaneously.At the same time,it also avoids the problems encountered in the application of traditional hydrological models such as the uncertainty of the model structure and parameters,and the inability to simulate the hydrological cycle under changing environment.(3)According to the socio-hydrologic analysis,in the Wuding River Basin,the groundwater recharge and the base flow decreased while the groundwater exploitation increased from 1975 to 2010.Under the influence of these three driving factors,the groundwater storage variation showed a downward trend.The groundwater storage variation was almost negative after the 1990 s,which indicates that the groundwater storage decreased.Climate change reduces evapotranspiration while the change of water intake and underlying surface make evapotranspiration increase.Under such a comprehensive effect,the evapotranspiration in basin showed a downward trend.Climate change has the largest impact on evapotranspiration,which makes itself the main reason for the decrease of evapotranspiration in basin.Climate change and groundwater storage variation led to an increase in runoff,while changes in the water intake and the underlying surface resulted in a decrease in runoff.As a result of these four driving factors,the runoff in the Wuding River Basin showed a significant downward trend.Climate change and underlying surface change have large number of but opposite effects on runoff.It can be found that the change in underlying surface should be the main reason for the reduction of runoff.(4)The socio-hydrologic model was established in Wuding River Basin.Taking 2011 as the typical year,based on the social hydrological status of the Wuding River from 1975 to 2010,the runoff and groundwater storage variation in the Wuding River Basin were simulated under four combined scenarios of social water intake and underlying surface conditions.The simulation results show that the water intake activities have little effect on the change of runoff but would cause changes in groundwater storage.And changes in the underlying surface would cause large changes in the evapotranspiration of the river basin,which would have a greater impact on runoff.Therefore,in the future,measures can be implemented to restore surface water and groundwater resources in the Wuding River Basin such as adjusting water use structure to reduce groundwater extraction,improving water use efficiency,controlling the change of the underlying surface,adjusting land use structure and so on.