三峡水库调蓄与海平面上升对长江河口土壤盐渍化演变的影响机制研究与情景模拟

The characteristics of the fragile ecological environment in the Yangtze River estuary is with low-flat terrain and poor salt-water excretion, and soil salinization is one of the most important limiting factors that affect ecological environment and agriculture in this area. Mutual effect of sea-level rise and impoundment of the Three Gorges Dam (TGD) will alter hydrological regime of the Yangtze River system and seawater intrusion situation. Thus the mutual effect will lead to great changes of salt movement of both surface and ground water, and salt-water dynamics and soil salinization in the Yangtze River estuary. In this fund item, we will systematically use combination of several methods, such as stationary experiment of field salt-water dynamics, field and laboratory parameters experiments, historical data analysis, numerical model and scenario analysis method, in order to study the comprehensive impact of TGD impoundment and sea-level rise on salt-water dynamics and soil salinization, and also carry out scenario analysis for the sake of predicting and evaluating the impact of interactive effect on soil salinization. In the process of the research, we will focus on evolution characteristics study of salt-water dynamics and soil salinizaiton under interactive effect of the TGD impoundment and sea-level rise, in order to explain the integrated drive mechanism of the mutual effect. Also, scenario analysis of evolution of salt-water environment and soil salinization under influence of multiple factors in estuary will be carried out, for the purpose of predicting and evaluating interactive effect on soil salinization. The study is of important theoretical value in deeply clarifying the impact mechanism of interactive effect of TGP and sea-level rise on soil salinization in this area, and it is of practical significance in the establishment of prevention system against soil salinization.

长江河口区地势低平，水盐排泄不畅，生态系统脆弱，土壤盐碱为影响该区生态环境和农业生产的重要障碍因素。三峡水库调蓄与海平面上升过程可能造成河口水情和咸水入侵的改变，进而影响长江河口区地表水与地下水盐分迁移、水盐动态与盐渍化演变特征，增加河口区土壤盐渍化发生风险。本项目拟通过野外定位监测与调查、参数试验、历史数据分析、模型研究、情景分析等方法，系统研究三峡水库调蓄与海平面上升交互作用对长江河口水盐动态与土壤盐渍化演变的影响，并对其影响进行情景分析与评估预测。拟重点研究三峡水库调蓄和海平面上升交互作用下河口土壤盐渍化演变特征，阐明其对长江河口水盐动态和土壤盐渍化演变的影响机制，开展长江口多驱动因素作用下土壤盐渍化演变的情景分析并评估其影响程度。本研究对深入阐明调蓄与海平面上升对长江口土壤盐渍化演变的交互作用机制具有重要理论价值，对科学评估交互作用影响和建立防控对策技术体系具有重要实际应用价值。

长江河口区地势低平，水盐排泄不畅，生态系统脆弱，土壤盐碱为影响该区生态环境和农业生产的重要障碍因素。三峡水库调蓄与海平面上升过程可能造成河口水情和咸水入侵的改变，进而影响长江河口区地表水与地下水盐分迁移、水盐动态与盐渍化演变特征，增加河口区土壤盐渍化发生风险。本项目通过野外定位监测与调查、参数试验、历史数据分析、模型研究等方法，系统研究三峡水库调蓄与海平面上升交互作用对长江河口水盐动态与土壤盐渍化演变的影响，并对其影响进行分析与评估预测。本项目研究了三峡调蓄和海平面上升交互作用下长江河口水盐动态变化规律，分析了三峡调蓄与海平面上升交互作用对长江口地下水环境的影响作用，研究了地下水环境对土壤水盐动态的影响，阐明了三峡调蓄和海平面交互作用对长江河口土壤盐渍化的影响机制；通过非参数模型和水文地质模型，分析和预测了三峡水库调蓄和海平面上升的复合场景对长江口土壤盐分动态的影响。 研究表明三峡水库调蓄通过改变入海口流量影响长江河口海水入侵，而海平面上升直接影响河口的海水入侵形势，进而两者复合作用影响河口江水盐分的变化。水文地质概念模型结果反映，江水对地下水有较强的补给作用，定水头对河口地下水的输入起了重要作用，其抬升了地下水位，将盐分带入地下水系统，而地下水位和地下水盐分是影响土壤盐分最重要的因素。通过评估和预测，三峡调蓄和海平面上升叠加影响下，河口土壤盐分含量将有所上升。