内蒙古高原内陆草原区河水水位波动下地表水与地下水转化关系研究

Interaction of surface water and groundwater is a key but very unclear part of the hydrological cycle processes and water resources assessment in inland steppes of the Inner Mongolian Plateau. The water shortage has restrained the development of local agriculture and stock farming，and also has threatened the fragile ecological system which mainly rely on the groundwater resources. As the development of water conservancy projects in steppe, interactions between surface water and groundwater become more complicated, and conjunctive use of surface water and groundwater is strongly required in inland steppes. Based on the observations and experiments for groundwater dynamics and water cycle, seasonal variation characteristics of groundwater recharge, runoff and discharge will be analyzed, interaction of surface water and groundwater will be revealed, and the influence of dam-induced river stage fluctuations to surface water and groundwater interactions will be explained using the water chemistry and isotopic tracing methods of rainwater, river water, soil water and groundwater. This study will be contributed to enrich and develop hydrological cycle theory in inland steppes and will also be helpful to provide theoretical and technical support for the alleviation of the regional water shortage and development conjunctive use of surface water and groundwater.

地表水和地下水转化关系是内蒙古高原内陆草原区水循环过程和水资源评价研究中十分关键且研究严重不足的部分。水资源短缺制约着内陆草原区农牧业发展，同时也威胁主要依赖于地下水资源的脆弱草原生态系统。随着草原水利事业的发展和完善，地表水和地下水相互转化关系变得更为复杂，建立地表水与地下水合理联合利用模式已成为我国内陆草原区水资源管理所面临的亟待解决的问题。本项目以草原区典型内陆河流域的野外系统水文观测和试验为基础，结合对大气降水、河水、土壤水以及地下水的水化学和同位素示踪分析，研究地下水补、径、排季节变化特征，揭示流域尺度地表水与地下水转化关系，阐明大坝或者强降水影响下河水水位快速波动对河段尺度地表水与地下水转化关系的影响。研究结果将丰富和发展内陆草原区陆地水循环理论，对缓解区域水资源短缺和发展联合管水用水新思路提供理论和技术支撑。

阴山北麓草原区属于我国北方重要生态安全屏障的组成部分，水资源短缺严重制约区域生态安全。通过野外调查与监测、同位素示踪、遥感解译等综合手段对艾不盖河这一阴山北麓典型流域分析可知，近些年来流域南部人类活动密集区农田面积扩张、天然植被退化明显，中部和北部覆被情况有所改善；1954年以来的年降水量、季节降水量均不具有显著增加或者减小趋势，但6月和8月降水量分别具有显著增加和显著减小的趋势，且降水天数（特别是夏季）具有显著递减趋势，突显出该区域集中降水期提前和降水更加集中在少数几次降水事件中的气候变化特征；流域地下水来源于大青山北部山区沿基岩裂隙快速下渗的大气降水，浅层地下水循环周期在5到10年；北纬约41.4°N以及42.1°N的两条带状湖群是地下水两次转换为地表水的关键带，地下水贡献比例约为30%；山区以北高平原等地区降水下渗以及蒸发影响深度主要集中在地下1m范围内，地下0.3m植被根系密集区出现土壤干层和钙质化；水库下游河道多为干枯无水状态，地表水与地下水之间的水力联系脱节，当河水位上升1.2m左右时河岸蓄水带宽度可达到126m。本项目揭示了阴山北麓草原区水循环规律，对流域地下水与地表水的统一规划，联合开发，缓解流域水资源短缺，保护脆弱生态环境，具有指导意义。