Department of Water Engineering and Management, Tarbiat Modares University, P.O. Box 14115-336, Tehran, Iran.
Water Engineering and Management Research Institute, Tarbiat Modares University, P.O. Box 14115-111, Tehran, Iran.
J Contam Hydrol. 2021 Jan;236:103753. doi: 10.1016/j.jconhyd.2020.103753. Epub 2020 Dec 2.
Seawater intrusion (SWI) is influenced by a variety of coastal phenomena, such as sea level rise (SLR), inundation of low-lying coastal regions, coastal storms, recharge rate variations, and pumping-induced saltwater upconing. Quantification of the influence of heterogeneity in the hydraulic conductivity field on SWI combined with SLR, land-surface inundation, and recharge rate variations in an unconfined aquifer is the main objective of the present study. The principal SWI indicators used in this study are length of the SWI wedge, seawater volume, and weighted average transition zone width. Characterized by the hydraulic conductivity field variance (σ), the longitudinal correlation length (λ), the type of SLR (gradual or instantaneous SLR), the land-surface inundation consideration, and the recharge rate variations, 72 scenarios have been introduced, and for each of them, 50 sets of heterogeneous hydraulic conductivity fields have been generated. Based on two approaches, namely ensemble Monte-Carlo and a Bayesian framework, it is demonstrated that: (1) the land-surface inundation consideration increases the SWI wedge length and the seawater volume regardless of the type of SLR, while it decreases the weighted average transition zone width in gradual SLR scenarios; (2) λ has a more significant impact on SWI characteristics compared to σ; (3) increasing the degree of aquifer heterogeneity results in larger effective dispersion values; (4) Numerical bootstrapping suggests that the introduced Bayesian framework could be adopted as an alternative to computationally demanding methods such as bootstrapping for stochastic analysis of SWI; (5) Reliability analysis indicates the general belief that considering the heterogeneity decreases the SWI wedge length and the seawater volume, while increases the transition zone width compared to the homogeneous modeling is associated with huge amounts of uncertainty proportional to the aquifer heterogeneity itself; and (6) the results show that the impact of heterogeneity on the SWI indicators is similar under different recharge rates.
海水入侵（SWI）受到多种海岸现象的影响，例如海平面上升（SLR）、沿海低地淹没、沿海风暴、补给率变化以及抽汲引起的盐水上涌。本研究的主要目的是量化水力传导率场的非均质性对 SWI 的影响，同时考虑 SLR、地表淹没和补给率变化在无压含水层中的作用。本研究中使用的主要 SWI 指标包括 SWI 楔形的长度、海水体积和加权平均过渡带宽度。考虑到水力传导率场方差（σ）、纵向相关长度（λ）、SLR 类型（逐渐或瞬时 SLR）、地表淹没考虑和补给率变化，引入了 72 种情景，并为每种情景生成了 50 组非均质水力传导率场。基于集合蒙特卡罗和贝叶斯框架两种方法，结果表明：（1）无论 SLR 类型如何，地表淹没考虑都会增加 SWI 楔形的长度和海水体积，而在逐渐 SLR 情景下会降低加权平均过渡带宽度；（2）与 σ 相比，λ 对 SWI 特征的影响更大；（3）增加含水层的非均质性会导致更大的有效弥散值；（4）数值 bootstrap 表明，所提出的贝叶斯框架可以作为替代计算量大的方法，例如用于 SWI 随机分析的 bootstrap；（5）可靠性分析表明，与均匀建模相比，考虑非均质性会降低 SWI 楔形的长度和海水体积，而增加过渡带宽度的普遍观点存在很大的不确定性，这种不确定性与含水层的非均质性本身成正比；（6）结果表明，在不同补给率下，非均质性对 SWI 指标的影响相似。
