华北平原咸水体运移对深层地下水开采的响应机理

Understanding the mechanism of salt water transport in response to the exploitation of deep freshwater has long been one of the major regional environmental hydrogeological problems and scientific challenges in the North China Plain. It is also the key to a correct understanding of the sources of deep groundwater pumpage. This study will look at the Hengshui - Cangzhou region as an area with typical vertical salt water distribution, and high levels of groundwater exploitation, integrating a variety of techniques in geology, hydrogeology, geophysics, hydrodynamics, and hydrochemistry - stable isotopes. Information about the problem will be determined using multiple lines of evidence, including field surveys of drilling and water sampling, as well as laboratory experiments and physical and numerical simulations. The project will characterize and depict the migration characteristics of salt water bodies and their relationship with the geological structure and deep ground water resources. The work will reveal the freshwater-saltwater interface shape; determine the mode and mechanism of hydrodynamic transport and salt transport; estimate the vertical migration time of salt water in a thick aquitard; and develop accurate hydrogeological conceptual models. This work will utilize groundwater variable density flow- solute transport numerical models to simulate the water and salt transport processes in vertical one-dimensional (typical bore) and two-dimensional (typical cross-section) space. Both inversion of the downward movement of saltwater caused by groundwater exploitation through history, and examining future saltwater migration trends under groundwater exploitation scenarios will be conducted, to quantitatively evaluate the impact of salt water migration to the deep groundwater body in the North China Plain. The research results will provide a scientific basis for the sustainable utilization of deep groundwater resources in this area.

华北平原中东部咸水体运移对深层淡水开采的响应机理，长期以来是该地区重大环境水文地质问题和科学难题之一，也是正确认识深部地下水开采来源的关键。本研究以衡水－沧州地区为典型研究区，利用多种技术手段，采用多信息相互验证的方式，通过野外调查、钻探取样，并采用室内物理模拟和数值模拟研究，综合地质、水文地质、地球物理、水动力、水化学-稳定同位素等多源信息，刻画咸水体运移特征及其与含水层系统结构和深层地下水开采的关系；揭示咸淡水界面运移的水动力学模式和盐分运移机理；估算咸水在厚层弱透水层的垂向运移时间；在准确概化水文地质概念模型的基础上，构建地下水变密度流－溶质运移数值模型，模拟垂向一维（典型钻孔）和区域二维（典型剖面）的水盐运移过程，反演过去地下水开采造成的咸水体下移，并预测其在未来不同开采情景下的运移趋势；定量评价华北平原咸水体运移对深层地下水的影响，为该地区深层地下水资源的可持续利用提供科学依据。

华北平原中东部咸水体运移对深层淡水开采的响应机理，长期以来是该地区重大环境水文地质问题和科学难题之一，也是正确认识深部地下水开采来源的关键。本研究以衡水－沧州地区为典型研究区，利用多种技术手段，采用多信息相互验证的方式，通过野外调查、钻探取样，并采用数值模拟研究，综合地质、水文地质、地球物理、水动力、水化学-稳定同位素等信息，刻画了咸水体运移特征及其与含水层系统结构和深层地下水开采的关系；揭示了咸淡水界面运移的水动力学模式和盐分运移机理。研究表明，黏土孔隙水中的盐分是百万年地质时间尺度内蒸发累盐的结果，浅层（0-30m）氯离子分布与全新世暖湿气候下的淡化有关；咸水在厚层弱透水层的垂向运移时间尺度是百万年；在准确概化水文地质概念模型的基础上，构建地下水变密度流－溶质运移数值模型，进行华北平原咸水运移与入侵演变趋势模拟，反演过去地下水开采造成的咸水体下移，以及未来不同开采情景下的运移趋势。模拟结果表明，氯离子垂向分布形态反映垂向向上的水力梯度（向上越流）。观测到的深层淡水含水层咸水入侵很可能是通过“天窗”，不是穿（粘土）层。评价华北平原咸水体运移对深层地下水的影响，可以为该地区深层地下水资源的可持续利用提供科学依据。