【作者】 马岚；

【导师】 魏晓妹；

【作者基本信息】 西北农林科技大学 ， 农业水资源与水环境工程， 2009， 博士

【摘要】 位于我国西北典型内陆干旱区石羊河流域下游的民勤盆地,由于地表来水量逐年减少,为了维持绿洲经济社会的发展,不得不大量开采地下水,导致地下水位大幅下降,引发了一系列生态环境问题,其危害程度和范围日益扩大。这不仅威胁民勤盆地自身的生存与发展,而且对甘肃省乃至西北地区的生态环境都会产生重大影响。研究和揭示该区地下水位动态的时空分布及变化规律,并对其进行合理调控,可为该区水资源合理开发利用和科学管理提供依据,对该区乃至广大西北内陆干旱区社会经济的可持续发展及生态环境重建有重要的意义。本研究分析了民勤盆地地下水位动态变化机理,在建立水文地质概念模型和数学模型的基础上,利用Feflow软件对模型进行了求解,模拟并预报了民勤盆地地下水位时空分布和动态变化过程。据预报结果选择了利于地下水位恢复的情景方案,对地下水位进行了调控,从而为该区的水资源管理和生态环境恢复与重建提供了理论依据。主要研究结果如下:(1)民勤盆地地下水系统是一个开放性的自然-人工复合系统。近二十多年来,受人类活动强烈干扰的区域地下水位逐年下降,年内呈季节性波动,且地下水位下降速度从绿洲腹地到绿洲边缘再向荒漠区逐渐减缓。自然因素(降水和蒸发)对民勤盆地地下水位动态变化的影响较小,而人为因素(渠系及田间入渗补给与地下水的开采)是驱动地下水位变化的主要因子。(2)在民勤盆地水文地质概念模型概化的基础上,构建了地下水位Feflow数值模拟模型。以GIS平台为依托,实现了民勤盆地地下水系统源汇项和含水层水文地质参数的模型输入,通过模型校验和模拟不仅获取了更合理和准确的水文地质参数,还实现了该区地下水位动态时空变化的可视化模拟。模型模拟效果良好,平均误差为0.9768m,模拟值与实测值之间的相关系数为0.977。(3)采用随机时间序列分析方法,对民勤盆地地下水系统源汇项进行了模拟预报,为实现用Feflow数值模拟模型进行地下水位预报提供了计算依据。该方法可有效解决资料缺少地区地下水系统源汇项的确定问题。(4)以2001年末民勤盆地地下水位实测值作为初始条件,采用Feflow和时间序列分析耦合的方法预报了2010年地下水位动态变化。与2001年相比,地下水位年内变化特征一致,即在开采灌溉期地下水位下降,在非灌溉期地下水位抬升,整体呈下降趋势,而在同地面高程下绿洲区水位较绿洲外围区水位低的程度更大,说明绿洲区水位下降速度大于绿洲外围区的趋势也越来越明显。同时,地下水位降落漏斗规模扩大,中心区地下水位埋深在增加。(5)根据《石羊河流域近期重点治理规划》,结合民勤盆地水资源开发利用现状,将2002年~2010年和2011年~2020年分别设定为地下水位下降减缓控制期和水位恢复期,并利用已建的Feflow模型对不同时期不同调控方案的地下水位动态过程分别进行模拟。结果表明,实现近期的地下水位下降减缓主要以确保红崖山水库年出库水量不减少和采取节水措施为主,使年出库水量和地下水开采量分别保持为7476万m~3和3.94亿m~3,并分别提高渠灌和井灌渠系利用系数至0.6和0.8。而恢复民勤盆地地下水位需在控制该区用水量和采取节水措施的前提下,通过外流域调水增大民勤盆地地表水量来实现。当年出库水量达2.7亿m~3时,盆地内地下水基本实现采补平衡,而当年出库水量为3.5亿m~3时,民勤盆地地下水位可得以有效恢复,特别是绿洲区域。更多还原

【Abstract】 The Minqin Basin is located in lower reaches of the Shiyang River Basin, which is a typical inland arid area in the Northwest China. As the surface water from upper reaches has been decreasing year after year, the groundwater has had to be over-exploited, which has made much decline of groundwater table, and has induced a series of eco-environment problems. The rapid deterioration of eco-environment is not only a threat to existing and development of the Minqin Basin, but also has significant influence on eco-environment of Gansu Province and even the Northwest China. Study on simulation and regulation of groundwater table dynamics of this area can provide guidance for reasonable exploitation and use and appropriate management of water resources, which is significant for sustainable development of social economy and rebuilding of eco-environment in this area and even northwest inland arid areas.This research analysed the mechanisms of groundwater table dynamics in the Minqin Basin. Based on the hydrogeological conceptual model and the mathematical model, the groundwater table Feflow numerical model was constructed, which simulated and predicted the space-time dynamics of groundwater table in the Minqin Basin. To effectively recover the groundwater table, the best scene of water resources exploitation and use was chosen, and the groundwater table was regulated, which can provide a theoretical guidance for water resources management in this area. The main research conclusions are as follows:(1) The Minqin Basin groundwater system is an open and compound system influenced by both nature and human. In the past twenty years, the groundwater table of this region influenced by intensive human activities declined year by year and fluctuated with seasons. The speed of groundwater table declination gradually got less and less from the oasis center to the deserts. The natural factors, including rainfall, evaporation and transpiration, had less influence on the variation of groundwater table, and the human activities, including ditch and field infiltration are the key driving factors in regulation of groundwater table dynamics.(2) Based on the hydrogeological conceptual model, the Feflow groundwater table numerical simulation model of the Minqin Basin was constructed. With the help of GIS plat, the in/out flow on top/bottom of the groundwater system and hydrogeological parameters were imported into the model. Via the simulation, not only the groundwater table space-time dynamics, but also the accurate hydrogeological parameters (conductivity and storativity) were acquired. Meanwhile, the viewdata of groundwater space-time dynamics could be acquired. In general, the model performed effectively with the mean error of 0.9768m and the correlation coefficient of 0.977 between the simulated and observed data.(3) In/out flow on top/bottom of the groundwater system was predicted with the time series analysis, which can provide important data for the Feflow model simulation. The method can effectively solve the problem of determining in/out flow on top/bottom of the groundwater system in the areas lacking data.(4) The groundwater table observed data of the Minqin Basin at the end of 2001 were set as flow initials, and the Feflow model and time series analysis were coupled to predict groundwater table dynamics in 2010. The groundwater table will have the same seasonal variation as that in 2001. The table will decline in exploitation and irrigation period, and will ascend in non-irrigation period, but in general, it will decline in the year. The water table in the oasis will all be lower than that out of the oasis with the same elevation, and their difference will be siginificant in 2010, which indicated that the water table in the oasis would be declining obviously faster and faster with time than that out of the oasis. Meanwhile, the groundwater depression cones would be expanding continuously, and their center depths would be increasing.(5) According to“the Current Key Fathering Layout of the Shiyang River Basin”and the reality of exploitation and use of water resources of the Minqin Basin, the period of 2002~2010 and 2011~2020 were respectively set as the phase of alleviating the water table declination and the recovery phase of water table, and the dynamic processes of water table in different periods under the different regulation schemes were predicted respectively with the built Feflow model. To alleviate the water table declination in 2002~2010, it is necessary to keep the output flux of the reservoir as 7476×104m~3/a and the exploitation of groundwater as 3.94×108m~3/a, and to take some water-saving measures by respectively increasing water use efficiency of ditch and well irrigation to 0.6 and 0.8. To recover the water table in 2011~2020, the control of water consumption and water saving are the prerequisite. Meanwhile, it is necessary to increase output flux by delivering water from the other river basins. Under the output flux of 2.7×108m~3/a, a balance state between recharge and discharge of groundwater will be possible; under the output flux with 3.5×108m~3/a, the water table of the Minqin Basin will rise again significantly, especially in the oasis.更多还原