| About 66.7% of global ecosystem services are degraded to varying degrees.The water conservation service is the key to sustainable social development and ecosystem stability as a combination of various services such as precipitation interception,water supply and water purification.The Yangtze River Delta Ecological Green Integration Demonstration Zone is located in the junction area of Shanghai,Jiangsu and Zhejiang,with a wide range of river and lake systems in the region and superior water resources endowment.The Taipu River flows through the three areas and is positioned as a "clear water corridor" in the watershed,with outstanding ecological and environmental value.The upstream Jiangsu section is economically developed along the line,with high utilization rate of shoreline development,and the demand for the Taipu River is mainly for flooding and drainage.Downstream,there are water intakes from Zhejiang and Shanghai,and the demand for the Taipu River is mainly for high quality water.Shanghai,Jiangsu and Zhejiang are positioned differently and face conflicts and challenges in the upstream and downstream water environment protection synergy.Delineate the function of the watershed water function areas that dovetail with the plan to become a key factor limiting the integration of the demonstration area water ecological services to improve the function.It is necessary to carry out a study on the spatial and temporal changes of water conservation services in the integrated demonstration area,and explore the response of water conservation services to multi-situational land use,in order to provide a scientific basis for regional flood control and drainage,water supply security.Based on the multi-source data and the water content module of InVEST model,this paper quantifies the water content capacity of the integrated demonstration area from the perspective of ecosystem services and explores the spatial and temporal variation characteristics of water content.The main drivers of upstream and downstream water content were also identified through correlation and principal component analysis by combining meteorological and land use factors.On this basis,three scenarios of baseline,planning control and ideal expectation are proposed from the perspectives of "increase in water content" and "increase in stability of water content capacity".The PLUS model and InVEST model were coupled to predict the function of water connotation services in the integrated demonstration area and to quantitatively explore the response of water connotation services to multiple scenarios of land use.Finally,the results of the study are combined to provide suitable countermeasures and suggestions for the regional synergy of the water conservation service function of the demonstration area.The main findings of the study are as follows:(1)The spatial and temporal variability of water content in the integration demonstration area from 1990 to 2020 is strong.(1)Temporally,the water connotation capacity of the integrated demonstration area is unstable,and the water connotation volume shows a trend of first decreasing,then increasing and then decreasing.Among them,the period of 2005-2015 is the stage of significant increase in water content.The water content of this phase increased by 651.94 mm,and the areas with larger increments were distributed in the upstream Wujiang District,as this area has water source and several ecological wetland reserves,which contributed to the increase of its water content.The increase in water conservation during this period amounted to134.08%,and the areas with larger increases was located in the downstream Qingpu District,which carried out several rounds of special plans for water environmental protection during this period,which significantly improved its water conservation capacity.(2)During the study period,spatial differences in water content persisted for a long time,showing a spatial distribution characteristic of high in the northwest and low in the southeast.Local spatial autocorrelation reveals that the northwestern part of Wujiang District shows high-value clustering,but the Wujiang section along the Taipu River shows a shrinking trend The western part of Qingpu is located in the water source protection zone and the eastern part of Qingpu is located in the Hongqiao hub,which is highly developed and utilized.(2)The correlation between land use,rainfall,potential evapotranspiration,and water content is significant.Land use type is the main driver of spatial variation in water content in integrated demonstration areas.(1)Water bodies and woodlands have a greater influence on the upstream water content.The factor loadings of water bodies are above 0.90 and up to 0.968 in the long term.the factor loadings of woodlands are above 0.70 and up to 0.961.(2)The influence of water bodies and construction land on the downstream water content is large.The factor loadings of water bodies are above0.90 and up to 0.972 for a long time.the factor loadings of construction land are around0.5 and up to 0.836.(3)In the future,we can improve the water connotation capacity of the integrated demonstration area by "increasing the quantity and improving the quality".Firstly,we can increase the water connotation capacity by increasing the proportion of forest land and water bodies and reducing the proportion of construction land.Secondly,on the basis of regulating the proportion of land types,the existing land types should be monitored and protected so that the water connotation capacity can remain stable in the long term.(3)From the viewpoint of water content and stability of water content capacity,three scenarios of baseline,planning control,and ideal expectation are proposed by setting different land development probabilities.(1)Baseline scenario: It is assumed that the probability of land development from 2015-2035 is the same as that from 1995-2015.Under the baseline scenario,the overall regional water content increases and the water content decreases in some areas of the upper Wujiang District.(2)Planning control scenario: Based on the baseline scenario,the probability of transferring cropland,forest land,grassland and water bodies to construction land is reduced by 30%,30%,20%and 20% respectively,and the probability of converting construction land to forest land is increased by 10%.Under the planning and control scenario,the amount of water content has increased in all areas compared to the baseline scenario.The water content of some upstream areas decreased under the baseline scenario and increased under the planning control scenario,with an increase of 16.03 mm or 3.03%.The water content of the downstream Qingpu District increased by 40.80 mm,or 38.30%.(3)Desired scenario: Based on the planning and control scenario,important rivers and lakes such as Taipu River,Dianshan Lake and Yuandang are set as restricted conversion areas,while woodland buffer zones are set along the regional backbone rivers(Taipu River and Jiangnan Canal),and the buffer zone width is set with reference to the protection width of the clear water green corridor of the national land plan.The ideal expectation scenario shows a significant increase of 29.89 mm or 5.65% in the water content of some unstable areas in the upper reaches.The results of the study show that the dual measures of water content and water content capacity are significant for the improvement of regional water content capacity.(4)Water environmental protection in demonstration areas should be approached from the perspective of watershed and regional collaboration.On the one hand,from the perspective of the basin to improve the function and planning alignment of the basin water functional zoning.Spatial control of upstream and downstream land use in the future watershed with the positioning of the Clear Water Corridor to improve the spatial differentiation of water conservation service functions brought about by differences in land development intensity.On the other hand,t The region safeguards regional water security by setting ecological red lines for arable land,ecology,urban development and river and lake waters to limit development. |
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