小浪底大坝建设对黄河下游滨河湿地的影响及其修复途径

The worldwide disputes about the impacts of large dam on river or region ecosystem never stop in recent decades.Taking the typical riparian wetlands along the Yellow River downstream from Xiaolangdi Dam to Huanyuankou as example, this study focuses on the impacts of dam establishment on riparian wetland ecosystem in structure, ecological processes and functions by field survey, remote sensing image interpretation and field site observation methods. First, the current degeneration situation of downstream riparian wetlands from the Dam will be discovered by field survey. Second, the changes of land use patterns and the degradation processes of riparian wetlands after the impoundment of the Dam will be illustrated through multiperiod remote sensing image interpretation, and their driving forces will be found out. Third, the mechanism of riparian wetlands degradation will be clarified by studying the hydrological processes of riparian wetlands using field site observation. Furthermore, the recharge-discharge relationship and response features of river water and riparian groundwater will be illuminated, and then,the typical hydrological transitional zone and the key restoration riparian zone will be determined. Finally, based on the above researches, the feasible measures of riparian wetland restoration will be put forward. This sdudy aims at the post evaluation of the environment impacts of the Dam on riparian wetlands and their restoration from a new angle of view. As expected, the results, on one hand, will give references and case experiences for the feasibility demonstration and decision-making on dam establishment and post ecological restoration in similar conditions. On the other hand, it will provide methodology for the ecological restoration of the degraded riparian wetlands along the Yellow River downstream from Xiaolangdi Dam.

国内外关于大坝建设的生态环境影响问题一直存在着持续的争论。本研究选择小浪底大坝以下黄河干流两侧滨河湿地为研究对象，采取野外调查、遥感影像解译、野外定位实验研究相结合的方法，系统开展滨河湿地生态系统结构、过程和功能对大坝建设的响应变化特征研究。阐明大坝下游滨河湿地生态系统基本特征及其退化现状，揭示研究区土地利用格局变化特征、退化过程及其驱动力，并系统开展滨河湿地水文过程研究，揭示湿地退化机制，阐明地下水与河水补排关系及响应特征，确定典型滨河水文交错带和生态修复关键地带，在此基础上，提出有针对性的滨河湿地生态修复途径。本研究的开展，一方面从滨河湿地退化现状、退化过程、退化机制入手，系统开展大型库坝建设的生态环境影响后评价研究，从而为相近条件下库坝建设的论证与决策，以及建成后河道两侧滩区湿地的生态修复提供借鉴和案例积累；另一方面，为小浪底大坝下游滨河湿地生态保育、功能恢复提供支撑。

本研究以小浪底大坝下游至郑州花园口黄河干流两侧滨河湿地为研究对象，采取野外调查、遥感影像解译、野外定位试验相结合的方法，系统开展滨河湿地生态系统退化特征对大坝建设的响应特征研究，提出了典型滨河湿地生态修复途径。研究结果表明：河道两侧滩区原有的滨河湿地退化现象严重，残存的零星植物群落中，草本植物占明显优势；大坝下游黄河干流两侧滩区农田、人工湿地和建设用地增加，河流、裸地和林地减少，土地利用变化过程主要为“裸地→农田→建设用地”、“裸地→河流→农田”、“裸地→林地→农田”、“农田→裸地→河流”4种类型。典型研究区滩区地下水位受黄河水位涨落和农业灌溉的双重影响，农田灌溉井进行抽水时，会在抽水井周围形成降落漏斗，但抽水时各个灌溉井之间相互影响较小；大坝建设造成滩区人类活动加剧，已经使地下水水质受到明显的影响。大坝蓄水运行后，下游滨河湿地地下水与河水的相互作用由以漫滩洪水垂直补给地下水向以河流侧向补给过渡，黄河南岸地下水补给河水，调水调沙期河水反补给地下水；黄河北岸，河水长期补给地下水，调水调沙期间补给增强。黄河北岸，距离河道2000 m左右的区域为典型的滩区河流-地下水的水文交错带，距离河道1000 m左右的区域内应作为典型的滩区生态修复关键地带；黄河南岸，距离河道400 m左右的区域内为典型的滩区河流-地下水的水文交错带，距离河道200 m左右的区域内应作为典型的滩区生态修复关键地带。基于保护湿地的同时兼顾周围社区居民的利益的原则，提出了“以河流为中心，按照‘河床自然湿地建成湿地保护区-生态修复关键地带建成植被缓冲区-滨河水文交错地带建成人工湿地-河漫滩外围区域建成农作物种植区’向外辐射以及适度发展生态旅游”的湿地保护与合理利用模式。