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首页> 外文期刊>Advances in Water Resources >Dispersion effects on the freshwater-seawater interface in subsea aquifers
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Dispersion effects on the freshwater-seawater interface in subsea aquifers

机译：分散对海底含水层中的淡水-海水界面的影响

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摘要

Recent recognition of the widespread occurrence of freshwater beneath the ocean has renewed interest in approaches to understand and predict its extent. The most straightforward methodologies are based on the sharp-interface approximation, which neglects dispersive mechanisms. The understanding of dispersion effects on freshwater extents in coastal aquifers is based almost entirely on onshore aquifer situations. This study explores dispersion in offshore coastal aquifers, in terms of the steady-state freshwater extent, seawater circulation and freshwater discharge, through numerical experimentation. Results show that increasing dispersion causes a seaward shift in the interface toe location, as expected, whereas the interface tip shows a non-monotonic relationship with dispersion that depends on the contrast between aquifer and aquitard hydraulic conductivities. Higher dispersion leads to enhanced seawater recirculation rates and freshwater discharge, as opposed to non-monotonic relationships obtained previously for onshore aquifers. The mixing zone at the toe widens as dispersion increases, similar to onshore cases, whereas the mixing zone at the tip has a surprisingly non-monotonic relationship with dispersion. The dispersion relationships revealed in this study can be explained by counteractions between dispersion, density and advective forces, and refraction across the aquifer-aquitard interface, which in combination produce offshore aquifer behaviour that differs, in some ways, to the manner in which onshore aquifers respond to dispersive processes. Consequently, previous empirical corrections to sharp-interface methods (to account for dispersive effects) applied to onshore coastal aquifers are ineffective in their application to offshore settings.
机译：最近对海洋下方淡水广泛存在的认识使人们对理解和预测其范围的方法重新产生了兴趣。最简单的方法基于尖锐的界面近似，而忽略了分散机制。对沿海含水层对淡水范围的扩散影响的了解几乎完全基于陆上含水层的情况。本研究通过数值试验，从稳态淡水范围，海水循环和淡水排放的角度探讨了近海沿海含水层中的分散性。结果表明，如预期的那样，分散度的增加会导致界面脚趾位置向海方向移动，而界面尖端显示出与分散度呈非单调关系，这取决于含水层和阿奎塔德水力传导率之间的对比度。与先前对于陆上含水层获得的非单调关系相反，较高的分散度导致提高的海水再循环率和淡水排放。类似于陆上情况，脚趾处的混合区域会随着分散度的增加而变宽，而尖端处的混合区域与分散体具有令人惊讶的非单调关系。这项研究揭示的色散关系可以用色散，密度和对流力之间的反作用来解释，并且可以通过整个含水层－阿奎塔尔界面的折射来共同作用，这些相互作用共同导致海上含水层的行为在某些方面不同于陆上含水层的方式。应对分散的过程。因此，以前对应用于陆上沿海含水层的锐界面方法（考虑到分散效应）的经验校正在将其应用于近海环境方面是无效的。

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