基于水供需服务流及外溢价值核算的太湖流域横向生态补偿机制

通过生态补偿协调流域内经济发展与生态保护的关系、缓解上下游利益相关者之间的矛盾是保障流域经济社会可持续发展的关键措施,而流域生态补偿核定的关键在于两点:一是如何模拟并量化水供需服务流动的流向、流量、流速及路径以明确供需双方及其空间关系;二是如何实现栅格尺度-地理单元-行政单元的尺度推演以实现不同行政单元之间生态系统服务的盈余、占用、外溢核算。整合卫星遥感、经济社会统计、水文气象观测等多源异构数据,集成水量平衡、水供需服务流动、生态价值核算等方法,构建了基于水供需流动及其外溢价值核算的流域横向生态补偿标准核定框架,利用D8流向法解决了水供需服务流动的流向、流量、流速及路径模拟与量化,实现了"栅格尺度-地形单元-行政单元"空间尺度推演的外溢价值核算,形成了流域内横向水生态补偿资金收取与分配方案。以太湖流域为例,在全面分析水资源外溢、占用及其价值的基础上,解析了县域尺度的水供需时空关系、流动路径及属性特征,辅以水质指标进而明确界定了责任方与补偿对象,形成了补偿资金收取与分配方案。结果表明,太湖流域水供需双方界线清晰、服务流近似于自然汇流过程,供给方以流域西部、西南部、中部县域为主,特别是西部至中部的县域,应受偿资金较多,平均各县应受偿资金比例超过2%/a,应受偿资金最多的嘉善区,比例超过19.66%/a;需求方聚集于流域中部、东部,特别是黄浦江自然汇流沿岸县域,应收取补偿资金较多,平均各县应收取资金比例超过5%/a,应收取最多的浦东新区,比例超过15.48%/a;净补偿资金基本呈现西高东低的分布特征,流域的大部分城市核心区的县域净补偿资金为负值。研究的核定框架、量化核算方法、资金统筹方案可应用到其他流域的横向生态补偿机制构建,实现流域内部与流域之间生态保护和经济发展的整体协调。

Horizontal payment for ecosystem services mechanism in Taihu Lake basin based on water supply and demand service flow and spillover value accounting

Coordinating the relationship between economic development and ecological protection in the basin and alleviating the conflicts between upstream and downstream stakeholders through Payment for Ecosystem Services (PES) is a key measure to ensure the sustainable economic and social development of the basin. The key of the basin PES accounting lies in two points: firstly, how to simulate and quantify the flow direction, flow rate, flow velocity, and path of water supply and demand service flow for clarifying the supply and demand sides and their spatial relationship; Secondly, how to realize the raster scale-geographic unit-administrative unit scale derivation, to achieve the surplus, occupation, and spillover accounting of ecosystem services between different administrative units. In this study, we integrated various heterogeneous data sources, such as satellite remote sensing, economic and social statistics, and hydro-meteorological observations. We employed methods including water balance, water supply and demand service flow, and ecological value accounting. We constructed an accounting framework for horizontal PES standard in the basin based on water supply and demand flow and its spillover value accounting.; The flow direction, flow rate, flow velocity and path of water supply and demand service flow were simulated and quantified by using D8 flow direction method. The accounting of spillover value was realized from the spatial scale of "raster scale-topographic unit-administrative unit". Finally, we designed a scheme for collecting and distributing horizontal water PES funds in the basin. Taking Taihu Lake basin as an example, based on a comprehensive analysis of water resources spillover, occupation, and their values, the spatial and temporal relationship between water supply and demand, flow paths, and attribute characteristics at the county scale were analyzed. The responsible parties and payment targets were defined in combination with water quality indicators and a scheme for collecting and distributing payment funds was formed. The results showed that the boundary between water supply and demand in Taihu Lake basin was clear. The service flow was similar to the natural confluence process. The supply side was dominated by the western, southwestern and central counties of the basin, especially the western to central counties, which should receive more payment funds, and the average proportion of each county should receive funds over 2%/a, and Jiashan District, which should receive the most funds, had a proportion of more than 19.66%/a. The demand side gathered in the central and eastern parts of the basin, especially in the counties along the natural confluence of the Huangpu River, which should pay more payment funds, with the average proportion of funds payable by each county exceeding 5%/a, and the largest proportion payable was Pudong New District, with more than 15.48%/a. The net received payment funds basically showed the distribution characteristics of high in the west and low in the east, and most of the counties in the urban core area of the basin had negative net received funds. The accounting framework, quantitative accounting method, and fund coordination scheme of this study could be applied to the construction of horizontal PES mechanisms in other basins to achieve the overall coordination of ecological protection and economic development within and between basins.