Vulnerability Indicators of Sea Water Intrusion

Abstract

In this paper, simple indicators of the propensity for sea water intrusion (SWI) to occur (referred to as "SWI vulnerability indicators") are devised. The analysis is based on an existing analytical solution for the steady-state position of a sharp fresh water-salt water interface. Interface characteristics, that is, the wedge toe location and sea water volume, are used in quantifying SWI in both confined and unconfined aquifers. Rates-of-change (partial derivatives of the analytical solution) in the wedge toe or sea water volume are used to quantify the aquifer vulnerability to various stress situations, including (1) sea-level rise; (2) change in recharge (e.g., due to climate change); and (3) change in seaward discharge. A selection of coastal aquifer cases is used to apply the SWI vulnerability indicators, and the proposed methodology produces interpretations of SWI vulnerability that are broadly consistent with more comprehensive investigations. Several inferences regarding SWI vulnerability arise from the analysis, including: (1) sea-level rise impacts are more extensive in aquifers with head-controlled rather than flux-controlled inland boundaries, whereas the opposite is true for recharge change impacts; (2) sea-level rise does not induce SWI in constant-discharge confined aquifers; (3) SWI vulnerability varies depending on the causal factor, and therefore vulnerability composites are needed that differentiate vulnerability to such threats as sea-level rise, climate change, and changes in seaward groundwater discharge. We contend that the approach is an improvement over existing methods for characterizing SWI vulnerability, because the method has theoretical underpinnings and yet calculations are simple, although the coastal aquifer conceptualization is highly idealized.

Comparison of the AVI, modified SINTACS and GALDIT vulnerability methods under future climate-change scenarios for a shallow low-lying coastal aquifer in southern Finland

“…Conversely, an increase in groundwater recharge causes a reduction in the GALDIT vulnerability index. In the coastal area, an increase in groundwater recharge will cause more groundwater discharge into the sea and hence a lower vulnerability to seawater intrusion, as also shown by Werner et al (2012).…”

Groundwater Flow Modeling in Coastal Aquifers: The Influence of Submarine Groundwater Discharge on the Position of the Saltwater-Freshwater Interface

“…The advantages of analytic solutions are that they are considerably less computationally intensive and require less data [11]. However, sharp interface approximations can only be used in areas where the mixing zone can be ignored; while, in reality, mixing between freshwater and saltwater occurs in all coastal aquifers as a result of dispersion, changes in head, changes in hydraulic conductivity and tides [25].…”

“…The Strack [6] analytic solution has *Corresponding author: Haile Arefayne Shishaye, Haramaya University, Dire Dawa, Ethiopia, Tel: +251942124463; E-mail: haile.4.hiwot@gmail.com been widely used by different researchers to explore seawater intrusion in coastal aquifers [1,5,[7][8][9][10]. Different seawater intrusion assessment methods have also been developed based on the Strack [6] analytic solution [11,12].…”

Saltwater Intrusion in Coastal Aquifers: A Primary Case Study along the Adriatic Coast Investigated within a Probabilistic Framework

“…The characterization of the mixing zone as well as the evolution of intrusion temporally represent some applications in which the adoption of numerical models is relevant [17,18]. Similarly, analytical formulations can provide a prompt insight into relevant physical processes involved and, for this reason, a significant number of studies have been conducted in this realm [19][20][21][22]. In particular, the theory developed by Strack [23], based on the sharp interface approximation, has been widely adopted to predict the extension of SI in steady-state flow under the Dupuit-Forchheimer assumption [3,20,24,25].…”