| Water shortage has become a major issue of the world’s sustainable development.The Yangtze River is the largest river in China and the third largest river in the world.Its rich water resource is of great significance to maintain people’s health and well-being and social development and stability.Under the impact of and anthropogenic and climatic change,the Yangtze River Basin(YRB)is facing the problems of water resources degradation,frequent floods,droughts,and ecological and environmental deterioration.Rencently,there are emerging challenges brought by the transformation from large-scale development to large-scale protection.Therefore,it is of great theoretical significance for the sustainable development,utilization and planning of water resources to(i)spatial-explicitly and quantitatively evaluate the water yield in YRB in the historical period,clarify the driving mechanism of water yield change and(ii)predict the future patterns of water yield,and evaluate the vulnerability of the water resources.In this study,the water yield of the YRB from 2000 to 2015 were quantitatively evaluated using the Integrated Valuation of Ecosystem Services and Trade-offs(In VEST)model based on climate,land use and soil data.The future water yield under four different integrated scenarios of socio-economic(Shared Socio-economic Pathways,SSPs)and climate(Representative Concentration Pathways,RCPs)were taken into consideration:SSP1-RCP2.6(Sustainable development path and low radiation forcing scenario),SSP2-RCP4.5(Intermediate path and moderate radiation forcing scenario),SSP3-RCP7.0,(Regional competition path and high and medium radiation forcing scenario),SSP5-RCP8.5(Fossil fuel driven path and high radiation forcing scenario);Then,multiple linear regression models were constructed to identify the relationship between the changes of climate,land use,socio-economic and landscape patter factors and the changes of water yield.Moreover,an indicator of water resources vulnerability was constructed to evaluate the water resources vulnerability level of YRB from natural environment and socio-economic aspects.Finally,the thesis raises suggestions for water resources management to cope with socio-economic and climate change in YRB.The main results and conclusions are as follows:(1)From 2000 to 2015,the total water yield showed an increasing trend,in which,from2000 to 2005,it showed a small decrease trend,and from 2005 to 2015,it showed an increasing trend.In 2000,2005,2010 and 2015,the total water yield was 1200.37 billion m~3,1136.09 billion m~3,1288.17 billion m~3 and 1319.44 billion m~3,respectively.The mean depth of water yield was 764.77 mm,705.23 mm,861.27 mm and 915.54 mm,respectively.The water yield decreased gradually from the southeast to the northwest of the YRB.The change of annual water yield from 2000 to 2015 involved the whole basin,the increase area was mainly distributed in the southeast of the YRB,and the decrease area was mainly distributed in the northwest of the YRB.(2)From 2000 to 2015,rainfall played a dominant role in shaping the change of water yield,with a contribution rate of 72.4%.The factors that had positive correlation with the change of water yield in YRB include:average rainfall,urban land area,IJI(Interpersion juxtaposition index)of unused land,SHAPE＿MN(Mean Shape index)of cultivated land;The factors that had negative correlation with the change of water yield in YRB include LPI(Largest patch index)of forest,AREA＿MN(Mean patch size)of urban land,NP(Number of patch)of cultivated land and per capita GDP(Gross Domestic Product).Socio-economic factors such as per capita GDP mainly affect the change of water yield through the interaction with the average rainfall,ET0(Evapotranspiration),the area of forest and the LPI of forest.The interaction between the area and LPI of woodland and socio-economic factors was significant:(i)The interaction with the area of forest showed that it promoted the increase of water yield under the condition of low per capita GDP(less than 30000 CNY,Chinese Yuan,k=9.97).(ii)The interaction with LPI of forest showed that LPI lowered water yield at low per capita GDP(k=-45.27).The water yield across the YRB was found to be highly spatially heterogenous.Contrary to the historical period,the water yield were projected increase in the northwest,while decrease in the southeast of YRB.(3)under the four integrated scenarios of socio-economic and climate change,except for the water yield under SSP1-RCP2.6 scenario in 2100,the water yield was projected to reduce in 2050 and 2100 in YRB.In 2050,the greatest reduction of 10.61%in water yield was projected under SSP3-RCP7.0 scenario,owing to 4.25%reduction in maximum rainfall in this scenario.Among the four scenarios,the SSP1-RCP2.6 scenario was projected to have the strongest water yield function in the future,because the scenario has the largest increase in rainfall(by 3.77%in 2100).In addition,the water yield under SSP5-RCP8.5 was projected to decrease by 1.52%in 2100,which is resulted from an upurge in urban land area(95.82%),and rainfall(3.47%),and temperature(4.65℃).Under the four scenarios,the water yield near the Taihu Lake decrease most seriously,with a reduction rate of more than40%.(4)A comprehensive assessment of natural environment vulnerability and socio-economic vulnerability showed that the vulnerability level of water resources in YRB was generally mild in 2015,and the vulnerability level in the northwest was higher than that in the southeast.The change in water resources vulnerability under the four scenarios in the future will be smaller,and is projected to be mainly concentrated in the sub-watershed with Taihu Lake as the center,and the vulnerability level will rise from mild vulnerability in the historical period to moderately vulnerable.In this study,we demonstrated how the In VEST model could be empirically built to assess the spatial pattern of water yield in YRB.The results show that:from the historical period to the future period,the water yield of the YRB increased first and then will decrease,the vulnerability level of water resources in the sub-watershed centered on Taihu Lake will increase.The water yield was affected not only by natural factors(include climate and land use),but also by human factors(include landscape pattern and social economy).Based on the results of water yield simulation and water resources vulnerability assessment,the water resources management suggestions for YRB are put forward as follows:(i)allocation of water resource(build reservoirs to store water in flood season,release water in dry season and transfer water across river basins)needs to be optimized to deal with the problem of uneven spatial and temporal distribution of water resource;(ii)Centralized management and protection mechanism of cultivated land could be promoted to realize the win-win goal of enhancing water yield function and optimizing land planning;3)The adaptive countermeasures should be adopted to prevent the vulnerability of water resources in the sub-watershed centered on Taihu Lake.Our study could add new evidence and provide scientific basis for the application,management and planning of water resources in YRB. |
PDF Full Text Request