Research On The Supply And Demand Assessment Of Water Supply Services And Ecological Compensation In The Three Gorges Reservoir Area

Ecosystem services(ESs)are the basis for human survival and development,and water supply services(WSSs)are the storage and maintenance of water by the ecosystem,a very important service in the ecosystem that maintains the security of regional water resources.The Three Gorges Reservoir(TGRA)is the largest strategic reserve of freshwater resources in China,and its water resources security not only directly affects the ecological security of the entire Yangtze River basin,but also has a bearing on the sustainable socio-economic development of the Yangtze River basin.At the same time,the ecological compensation(EC)construction in the TGRA is related to the effectiveness of the concept of "transforming green water and green mountains into golden mountains",and is of great significance to the promotion of ecological civilization.This thesis assesses the supply and demand of WSSs and ecological compensation(EC)in the TGRA,using the period 2004-2020 as the study period.The thesis was carried out from a ’natural-social-economic’ perspective,using the InVEST model to assess the supply of WSSs in the TGRA,and the demand for WSSs in terms of water for agriculture,industry,domestic use and livestock.The spatial and temporal variation in the supply and demand of WSSs was explored.Secondly,a model was constructed to balance the supply and demand of WSSs,and the Freshwater Security Index(FSI)was introduced to analyse the security of freshwater resources in the TGRA.On this basis,a total of 13 drivers of the FSI under three categories of socio-economic,natural climate and sectoral water consumption were detected using a geographic probe.Finally,an EC model for WSSs in the TGRA was constructed.Based on the supply and demand of WSSs to determine the EC subject and object,the emergy value analysis theory was introduced to calculate the unit water resource value of each region,and the specific EC payment(paid amount)was calculated by combining the supply and demand surplus and shortage,and the correction coefficient;the ecological compensation priority sequence(ECPS)was introduced to explore the urgency of each administrative region for EC funds.The following main conclusions were obtained:(1)The thesis progress on ESs,WSSs and EC at home and abroad is reviewed in the context of regional WSSs supply and demand assessment and EC research.With the development of remote sensing and GIS technology,spatial analysis models can be effectively applied to the study of ESs,while the demand for ESs is also gaining more and more attention.Secondly,based on the ecology and economics of EC for WSSs and other related theoretical foundations,combined with the spatial heterogeneity of natural resources and social economy in the study area,it is found that it is urgent and necessary to conduct scientific and objective research on WSSs supply and demand assessment and EC in the TGRA.(2)A quantitative model of WSSs supply and demand in the TGRA and a supply-demand balance model were constructed,and geographic probes were used to detect 13 drivers of FSI in the TGRA under three categories of natural climate,socio-economic and sectoral water consumption.The main findings are:(1)The supply of WSSs shows an upward and then downward trend,with the head and tail areas of the TGRA being the low value areas for water yield,while the hinterland areas are the high value areas for water yield.The land use type with the highest water production is forest,and urban construction land such as impervious surface has a high water production capacity per unit of land area.The demand for WSSs shows a trend of increasing and then decreasing,with relatively high water consumption in the tail and central parts of the reservoir belly and low water consumption in the head of the reservoir.Agricultural water use is the main water use in the TGRA,accounting for 44.67% of the total multi-year water consumption in the TGRA.(3)The overall supply of WSSs was greater than demand during the study period,and the FSI showed an upward trend,with the number of districts and counties with water shortages first rising and then falling.The FSI values of the key ecological function areas in the TGRA were higher,while the FSI values of the reservoir tail areas located in key development zones were lower.(4)The analysis of the geodetector results shows that industrial water use has the strongest explanatory power for FSI in the TGRA,and evapotranspiration has the weakest explanatory power for FSI.The way technology is produced affects the efficiency of water consumption,thus making the contribution of drivers to FSI change.(3)On the basis of clarifying the stakeholders of EC,an EC standard model was constructed,using the market value method,combining energy value analysis theory and correction coefficients to obtain differentiated EC standards;an ECPS model was constructed to explore the urgency of EC in each region and to clarify the priority targets for compensation.The main findings of the study are as follows:(1)The value of water resources per unit is lower in areas with relatively high WSSs supply,while the value of water resources per unit is higher in areas with lower WSSs supply.(2)The paid areas for EC for WSSs in the TGRA are all located in the hinterland and the head of the reservoir,and the number shows a trend of first decreasing and then increasing.The areas paid for EC for WSSs are concentrated in the core area of the main city of Chongqing at the end of the reservoir,with the number showing a downward and then an upward trend.The rate of increase in total compensation is much higher than the rate of decrease in total payments,reflecting the rising intensity of demand for EC in the TGRA and the overall increase in opportunity costs for regional economic development.(3)The overall ECPS of the TGRA decreases year by year,dropping by 88.46% in 2020 compared to 2004.The ECPS of Badong County and Xingshan County at the head of the reservoir,as well as the key ecological function areas in the reservoir belly,is high,at the first level of priority.The priority of EC in Yiling District at the head of the reservoir,the key development areas in the belly of the reservoir and the tail area of the reservoir is low,and is a fourth priority.Finally,based on the results of the theoretical study and model analysis,this paper puts forward the following policy recommendations: firstly,promote water conservation technology and optimise industrial structure;secondly,improve the education of residents’ ecological civilisation literacy;thirdly,build a comprehensive platform for EC;fourthly,explore market-oriented and diversified EC mechanisms,with a view to coordinating water ecological protection and economic development in the TGRA.