典型内陆盆地地下水系统演化及其生态响应研究

Groundwater is one of the most essential and sensitive factors directly related to the ecological system in inner-land basin of Northwest China. The change of groundwater level has resulted in a series of ecological problems such as the degradation of vegetation and wetland as well as the desertification in this region. However, the research of groundwater system and its ecological response is backward because of the shortage of basic data and the complex situation of hydrological cycle represented by the frequent interaction of surface water and groundwater. The principle of ecological response to groundwater dynamic becomes a hot topic in the inner land basin. The uncertainty of regional hydrogeological parameters is also a crucial problem concerning the groundwater model development in basin scale. Based on the early research results and by using comprehensive methods of grand observation, remote sensing, environmental isotope analysis as well as the computer simulation, this proposal aims to investigate the groundwater system and its evolution in Dunhuang basin which is located in Hexi Corridor of Gansu province. The aquifer structure, water flow and geochemical characteristics of groundwater system could be analyzed in basin scale.The spatial geo-statistics and quantization theory could integrated to determine the regional hydrogeological parameters. The groundwater concept model and its numerical model could be developed to simulate the flow variation under various scenarios of the different precipitation and water utilization schemes. The water source which sustains the oasis system in Xihu Nature Reservation in the basin, and the origin and composition, amount as well as their spatial and temporal variation could be determined by the comprehensive analysis of the investigations. The relationship model of ecological response model could be established by artificial neuron network (ANN) method. The research results could be expected to be very meaningful for the implementing of water resources planning and utilization as well as the ecological protection in the basin, also to enrich the theory of hydrological cycle in the inner-land basins.

地下水是维持内陆盆地生态健康极为关键、敏感的因子，植被退化、湿地萎缩和荒漠化等都与地下水动态变化有着密切的关系。内陆盆地水循环具有复杂性，表现在地表水-地下水多次相互转化和人工干扰，地下水动态变化生态响应机制是需要突破的科学难题；由于基础资料不足，地下水模型参数不确定性问题有待研究。本申请在前人调查研究成果基础上，选择敦煌盆地作为研究区，通过地面调查、遥感、环境同位素、模拟技术等手段，从地下水系统介质场、水动力场和水文地球化学场等角度，开展盆地尺度地下水形成与演化机制研究。首次提出运用空间地质统计学和数量化理论解决区域水文地质参数不确定性。通过建立盆地地下水系统模型以及来水、用水情景模拟，掌握维持保护区绿洲生存的地下水来源、组成、数量及其时空变化规律。研究基于人工神经网络理论的地下水动态变化生态响应的定量分析方法，为流域水资源开发和生态保护提供科学依据；同时丰富完善内陆盆地水循环理论方法。

西北干旱区生态环境极其脆弱，由于降水稀少，地下水成为维持内陆盆地生态极为关键的因子。目前面临的区域性植被退化、湿地萎缩和荒漠化等都与地下水动态变化有着密切的关系。内陆盆地水循环具有复杂性，表现在地表水-地下水多次相互转化和人工强烈干扰等特点，地下水动态变化生态响应机制是需要突破的科学难题；另一方面，西北地区内陆盆地研究程度普遍低，基础资料不足，如何利用新技术，提高地下水模型精度也是重要课题。本项目选择了河西走廊西端的党河流域作为研究区，在以往调查研究成果基础上，通过地面调查、遥感、环境同位素和数值模拟等技术手段，从地下水系统介质场、水动力场和水文地球化学场等角度，开展盆地尺度地下水形成与演化，以及生态响应机制研究。主要成果和创新认识包括：（1）党河下游西湖国家级自然保护区湿地水源组成、数量与其变化规律：肃北-阿克塞盆地地下水接受党河水和阿尔金山诸小河河水补给，在盆地北部以泉集河或地下潜流形式补给北盆地的西湖保护区湿地，党河中游河水是西湖湿地主要水源之一。（2）西湖保护区湿地时空演化趋势与人为干扰生态响应分析：上世纪湿地退化速率大，疏勒河干流和党河干流水库修建，拦截地表来水是生态退化的主要原因；新世纪后，湿地退化趋势变缓，保护区上游南湖灌区开发和党河干流梯级电站开发是影响湿地退化的主因。（3）开发了党河流域南、北盆地地下水系统模型，模拟预测了“引哈济党”工程生态补水方案和生态修复，认为原规划的通过党河和疏勒河主河道补水到玉门关的补水方案不适宜。玉门关湿地处于下游，是地下水排泄区，增加西湖湿地补给是难以实现。本项目提出了在西湖湿地上游--西土沟冲洪积扇顶部故河道或洼地补水方案，可以抬升区域地下水位，增加湿地补给量，达到恢复湿地的目的。研究成果可以为流域水资源开发和生态保护提供参考；同时丰富完善内陆盆地水循环理论与方法。