潮汐波动对潜水含水层海水入侵规律的影响研究

The Influence of Tidal Oscillations on the Behaviors of Seawater Intrusion in Unconfined Coastal Aquifers

滨海潜水含水层的海水入侵过程会受到潮汐波动的影响。本文基于OpenGeoSys科学模拟软件,以动态潮汐边界作为海相边界,建立斜坡海滩潜水含水层海水入侵的二维剖面数值模型,探讨了潜水含水层水位波动及盐度运移规律,突破了传统海水入侵数值模拟过程中忽略潮汐影响的局限性。结果表明:潮汐作用改变了传统海水入侵模型的盐度分布规律及淡水排放通道;在定流量内陆边界条件下,潮汐作用会缩短盐水楔在淡水中的扩散距离,减缓了海水入侵的程度。本文有效地解决了数值模拟时考虑复杂海相边界时遇到的问题,通过数值模拟进一步揭示了潮汐波动影响下的海水入侵机理。本文的研究成果为合理优化开采地下淡水资源、定量评价与防治海水入侵提供科学的理论依据。

Tidal oscillations have significant influence on the process of seawater intrusion in unconfined coastal aquifers.Previous studies typically neglect or simplify oceanic oscillations such as the effects of tides.In order to investigate the tidal influence on the behavior of water level fluctuations and salinity transport in unconfined coastal aquifers,a numerical model is developed by considering and controlling dynamic tidal boundary conditions based on the scientific modelling package OpenGeoSys.A fixed flux condition is used at the landward boundary.The numerical simulation results were verified with the experiment results,which indicates that the moving boundary can accurately describe the tidal oscillations.And numerical results indicate that tidal oscillations change the salinity distribution and the fresh groundwater discharging zone,which leads to a significant reduction on the extension of seawater intrusion in unconfined coastal aquifers.When the landward boundary is fixed,the larger tidal amplitude has greater influence on the salinity distribution.When the tidal factors are fixed,smaller flux on the landward boundary will be more susceptible to the tidal oscillations.This work effectively overcome the numerical simulation difficulties encountered with complex seaward boundaries,and reveal the seawater intrusion mechanism under the influence of tidal oscillations.This research provides scientific and theoretical basis not only on properly exploring fresh groundwater resources,but also on effectively controlling seawater intrusion in unconfined coastal aquifers.