Metacoupling of Water Transfer: The Interaction of Ecological Environment in the Middle Route of China’s South-North Project

Abstract

At present, nearly half of the population of China live in water-deficient areas where water needs to be transferred from surrounding or remote water sources to meet local water demands. Although the water transfer project has alleviated the demands for water in the water-deficient areas, and brought water-supply income to water source regions, it has also posed some cross-regional negative impacts, including the changes in the original ecology within the water source, the impacts on the downstream water demands, and the risk of biological invasion in the distant water receiving areas. Therefore, it can be seen that the impact of water transfer is complicated and will be manifested in various aspects. The Middle Route of China’s South–North Water Transfer Project (SNWTP-MR), as the world’s largest cross-watershed water transfer project, exerts particularly important effects on regional sustainable development; however, it also produces complex interactions within the ecological environment itself, downstream and in the distant water receiving cities. Thus, this work attempts to apply a metacoupling analysis framework of water transfer to explore the ecological interaction of water transfer in SNWTP-MR on each system. The metacoupling framework can be divided into intracoupling, pericoupling and telecoupling. This study focuses on the analysis of the causes and effects of the intracoupling, pericoupling and telecoupling of SNWTP-MR from the perspective of ecological values and ecological risks. We found that the coupling of water transfer brings about 23 billion yuan of ecological service value to the water source annually, but also increases the internal ecological risk index by 9.31%, through the calculation of changes in land use; secondly, the power generation benefit significantly increases, and the flood control standards have shifted from once-in-20 years to once-in-a-century. However, the ecological risks are also significant, such as poor water quality, eutrophication of water resources, competition for water between industry and agriculture, deterioration of waterway shipping, and threats to biodiversity, etc. Considering only water supply, the population carrying capacity of the water resource in distant water receiving cities is increased by 16.42 million people, which enhances the value of water resources and creates a cross-regional green ecological landscape belt. Nevertheless, the biological invasion and water pollution have greatly affected the safety of water supply. It can be seen that the cross-regional water transfer does not always damage the interests of the sending system and the spillover system while benefiting the receiving system; its impacts are complex and variable. Through this paper, it is hoped to provide a reference for the analysis of the ecological compensation, resource development and allocation in SNWTP-MR by revealing the metacoupling relationship of SNWTP-MR. This paper will provide new ideas for researching the metacoupling relationship, thereby offering valuable reference for the study of the interaction generated by large-scale water transfer.

Effectiveness of groundwater extraction in Beijing since the ingauration of the first phase of the South-to-North Water Diversion Project, China

“…the Yangtze River, Yellow River, Huaihe River and Haihe River. This forms China's comprehensive water resources allocation pattern, known as the "four horizontal and three vertical" scheme (Su et al 2022). The central route draws water from Danjiangkou Reservoir in the middle reaches of the Yangtze River, travering Henan Province, Hebei Province, Beijing Municipality and Tianjin Municipality, to supply water for domestic, industrial, ecological, and agricultural use to 19 large and medium-sized cities and 100 counties (or county-level cities) within these regions, covering a total distance of 1 432 km (Liu et al 2023).…”

Progress and prospects of rural human-earth system coupling research

“…素调控和生产模式调整提升了耕地规模产能和生 态安全状况 [89] 。太行山荒坡地整治工程促使土地 资源向资产转化， 形成特色产业模式和农户参与机 制， 增加农民收入 [90] 。生态保护政策如生态补偿、 生态系统服务付费、 生态产品价值实现等通过建立 生态系统服务供给者与受益者之间的关联机制， 在 不同尺度和利益相关者之间协调农村生计改善、 区 域经济发展和生态环境保护 [91][92] 。密云水库上游 "稻改旱" 工程使农户生计由种植水稻向玉米转变， 水库水量和水质得到提升， 并且保证了下游北京居 民用水 [92] 。 政策工程实施也会产生意外后果， 例如干旱、 植被覆盖度等自然环境条件和放牧、 人口迁移、 非农 就业等生计活动改变会影响退耕还林的效果 [93] 。黄 土高原生态工程控制土壤侵蚀后， 黄河泥沙负荷减 少， 黄河下游三角洲转向侵蚀， 且大规模植被恢复 引起的蒸散量增加导致土壤干燥， 黄河天然径流量 下降 [44] 。耕地占补平衡政策实施下虽然耕地总量 已达到平衡， 但由于省际之间耕地补偿措施不当， 如林地转耕地导致植被碳储量显著减少， 特别是在 西南地区 [94] 。南水北调工程使输水地区丹江口水 库水源地生态系统服务和当地居民就业收入增加， 但使生态风险指数提高， 受水地区城市用水量增 加， 但也带来外来物种入侵风险。此外， 还会带来 调水沿线和长江流域水体富营养化、 水文和水生生 物量改变等溢出效应 [95][96] [42] 、 Tapio 脱钩 模型 [43] 、 耦合协调度模型 [49] 、 综合指数模型 [54] 为识别 乡村人地系统耦合的时空格局和演变特征提供了 重要手段。承载力模型和足迹模型广泛用于综合 表征人地关系和测度人地平衡状态 [97] 。新兴的社 会-生态网络方法在定量刻画人地系统结构、 分析 系统要素相互依赖的动态变化方面具有较大的应 用潜力 [45] 。在探究乡村人地系统耦合的影响因素 及作用程度上， 计量或空间回归分析、 归因分析等 是主要的研究方法。结构方程模型整合了因子分 析、 路径分析和回归分析， 同时可包含无法直接观 测的潜变量， 应用于农村生计研究中 [93] 。在人地耦 合效应评价尤其是资源环境效应评价上， 生命周期 评价和多区域投入产出模型已成为全过程经济活 动和跨区域资源环境影响分析的重要研究手段 [78] 。 可以看出， 基于要素指标和数理统计分析的乡 村人地系统耦合评价模型是研究主要采用的方 法。然而， 对于要素状态的刻画和关联影响的判别 未能深入揭示乡村人地系统动态过程和互馈机 制。目前自然要素过程模型较多， 社会经济及其与 自然要素耦合的过程模型相对较少， 耦合机理模型 的应用还处于起步阶段 [98] 。近年发展起来的多主 体模型(ABM) [99] 、 系统动力学模型(SD) [100] 、 综合评估 模型(IAM) [101] Bonn, Germany: IPBES, 2018.…”

Assessment of Multi-Regional Comprehensive Benefits of the South-to-North Water Diversion Project in China

“…The construction of the first phase of the east and middle routes commenced in 2002 and 2003, respectively, and water transfer began in 2013 and 2014. The west route is designed to transport water from the upper Yangtze River tributaries but remains in the planning stage because of challenging topographical and ecological factors [25]. The entire SNWDP has incurred a total investment exceeding CNY 240 billion and has necessitated the resettlement of more than 300 thousand people [26].…”