Density‐dependent surface water–groundwater interaction and nutrient discharge in the Swan–Canning Estuary
Density‐dependent surface water–groundwater interaction and nutrient discharge in the Swan–Canning Estuary
复制标题
DOI：
10.1002/hyp.303
复制
发表时间：
2001-09
影响因子：
3.2
通讯作者：
Anthony J. Smith;J. Turner
中科院分区：
文献类型：
--
作者：
Anthony J. Smith;J. Turner
西澳大利亚州斯旺-坎宁河口的盐度随季节变化，从冬季的淡水条件到夏季的海水盐度。现场观测表明，由此产生的河口和邻近的淡水地下水系统之间的季节性密度差异足以驱动混合对流单元，从而引起含水层中河水的循环。在这项研究中，我们研究了稳定的密度驱动的对流的作用，作为一种机制，有助于溶解的营养物质，特别是铵，斯旺-坎宁河口和当地地下水系统之间的交换。我们目前的结果，从二维（部分）和三维密度耦合流和质量输运模型，在比较与格洛弗的突然界面盐水入侵的解决方案。该模型的重点是发展的物理过程的理解，影响长期或平均对流行为的河口地下水。结果表明，对流稳定性主要取决于两个因素的相互作用：（1）河口与含水层之间密度差的向下不稳定浮力效应;（2）区域地下水流量的向上稳定效应。河口下的对流细胞的结构和地下水系统内的河口水的再循环率被证明是与流量修正瑞利数，严重依赖于含水层的各向异性和河口曲流模式。这些机制的河口水的再循环是负责运输高浓度的铵，观察在河口河床沉积物中的孔隙流体，进入地下水，并最终返回到河口。版权所有© 2001约翰威利父子有限公司。
Salinity in the Swan–Canning Estuary, Western Australia, varies seasonally from freshwater conditions in winter up to the salinity of seawater in summer. Field observations show that the resulting seasonal density contrasts between the estuary and the adjacent fresh groundwater system are sufficient to drive mixed‐convection cells that give rise to circulation of river water in the aquifer. In this study, we examine the role of steady density‐driven convection as a mechanism that contributes to the exchange of dissolved nutrients, particularly ammonium, between the Swan–Canning Estuary and the local groundwater system. We present results from two‐dimensional (section) and three‐dimensional density‐coupled flow and mass transport modelling, in comparison with Glover's abrupt‐interface solution for saltwater intrusion. The modelling is focused on developing an understanding of the physical processes that influence the long‐term or mean convective behaviour of groundwater beneath the estuary. It is shown that the convective stability depends fundamentally on the interplay between two factors: (1) the downward destabilizing buoyancy effect of density contrasts between the estuary and aquifer; and (2) the upward stabilizing influence of regional groundwater discharge. The structure of convection cells beneath the estuary and recirculation rates of estuary water within the groundwater system are shown to be related to a flow‐modified Rayleigh number that depends critically on the aquifer anisotropy and estuary meander pattern. The recirculation of estuary water by these mechanisms is responsible for transport of high concentrations of ammonium, observed in pore fluids in the estuary bed sediments, into groundwater and its eventual return to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.