近50年来我国北方典型区域地下水演化特征

文章在总结中国北方地下水最新调查成果的基础上，选择西北内陆盆地、华北平原和松嫩平原为典型区，对近50年来区域地下水系统的演变特征及其影响因素进行探讨。研究发现: 我国北方盆地和平原地下水系统演化具有渐变性和突变性特征，但在不同地区存在着差异，区域地下水系统已经变得脆弱，地下水资源可持续利用向不利的方向发展。地下水补给演变表现为山前平原地带的补给能力减弱，河道补给减弱或消失，中下游农业区地下水补给强度增大，总补给量呈现减小的趋势；  其中，西北内陆盆地下水补给的减少与上游水资源利用过度、渠系防渗程度提高有关；  而华北平原和松嫩平原地下水总补给量的减少与降雨量的减少和山区河流拦蓄水量的增加有关。伴随着补给模式的改变，地下水流场演变表现为普遍出现持续性的区域地下水位下降，西北干旱区表现为山前平原地下水位快速下降、泉流量减少、溢出带下移；  华北平原和松嫩平原表现为溢出带消失、水位降落漏斗形成并发展，区域地下水流被截断，形成以降落漏斗为中心的局部水流系统。地下水化学场变化主要表现为水化学类型变化、矿化度增大，污染组分增加。自西北内陆盆地至华北平原、松嫩平原，水化学变化强度明显增加，以华北平原和松嫩平原最为明显。本文在这些认识的基础上提出了应对气候变化与人类活动双重影响下地下水演变的适应性对策，为地下水资源可持续利用提供了理论依据。

GROUNDWATER CHANGES OF SELECTED GROUNDWATER SYSTEMS IN NORTHERN CHINA IN RECENT FIFTY YEARS

Based on the data of groundwater resource investigation in Northern China,the present work is to discuss the changes of regional groundwater regimes and its induced mechanism during the past fifty years by selecting the Junger Basin,the Hexi Corridor Basin,the North China Plain (NCP) and the Songnen Plain as representatives for different groundwater systems.The results suggested that the responses of groundwater system to the stress were characterized by gradual and sudden change resulting in degeneration of groundwater system,which restricted sustainable utilization of groundwater resources.The changes of groundwater recharge,flow pattern and chemical composition showed a slight difference in different basins and plains.Groundwater recharge area changed from the piedmont plain to the agricultural area in the lowland.As a result,the total rate of recharge for each basin tended to decrease during the past 50 years.This decrease of recharge rate in arid inland basins,was mainly caused by the excessive use of water in the watershed area and channel anti-seepage.While in the NCP and the Songnen Plain,the decrease of recharge rate related to reduced precipitation and increased river impoundment.As a result of decreased recharge,the groundwater level continued to decline in all basins and plains.In the arid inland basins,the groundwater level fell fast in the piedmont plains resulting in spring move towards lower location.In the NCP and the Songnen Plain,the cone of depression was formed that intersected the regional groundwater flow system and developed a local flow system center on the depression.The hydrochemical evolution of groundwater was characterized by change of water type,increase of TDS and pollutants,which was very significant in the NCP and the Songnen Plain.Finally,the authors presented the strategies to use and develop groundwater resources for mitigation and adaption to climate change.