Seawater Intrusion Vulnerability Research Articles

Development of Seawater Intrusion Vulnerability Index Using AHP

기후온난화로 인해 해수면 상승은 연안지역의 해수침투 피해를 야기했다. 해수침투에 대한 취약성 지수를 PSR 모형과 계층화 분석 방법(AHP)을 이용하여 개발하였다. 우리나라 삼면의 연안지역 중 강원도 속초시, 인천시 강화군, 충청남도 태안군, 전라남도 여수시, 진도군을 선정하여 인문, 경제, 사회, 환경 등의 자료를 바탕으로 14개 지표를 선정하였다. 스케일 재조정방법을 통해 지표의 표준화를 실시하고, 전문가들의 의견을 반영한 설문으로 얻어진 가중치를 부여하여 해수침투 취약성 지수를 산정하였다. 그 결과 전라남도 여수시가 해수침투에 가장 취약한 지역으로 선정되었다. 개발된 해수침투 취약성 지수는 해수침투 피해를 최소화 할 수 있는 향후 정책을 결정하는 중요한 도구 및 기초자료로 활용될 수 있을 것으로 기대된다. Sea level rise due to global warming causes seawater intrusion into aquifers in coastal areas. Seawater intrusion vulnerability index was developed using PSR (Pressure, State, Response) model and analysis hierarchy process (AHP). Coastal regions in Korea, Gangwon-do Sokcho-si, Incheon-si Ganghwa-gun, Chungcheongnam-do Taean-gun, Jeollanam-do Yeosu-si, Jindo-gun were chosen and 14 indicators were selected by considering the humanities, economic, social, environmental aspects. Re-scaling method was used for the standardization of indices and questionnaire survey was performed to calculate weight values for each index. The results showed that Yeosu-si was selected as the most vulnerable region to seawater intrusion. The seawater intrusion index developed in this research can be used to analyze the vulnerable regions to seawater intrusion and to establish a policy to minimize the seawater intrusion problems in coastal regions.

Intensively exploited Mediterranean aquifers: resilience to seawater intrusion and proximity to critical thresholds

Abstract. We investigate seawater intrusion in three prominent Mediterranean aquifers that are subject to intensive exploitation and modified hydrologic regimes by human activities: the Nile Delta, Israel Coastal and Cyprus Akrotiri aquifers. Using a generalized analytical sharp interface model, we review the salinization history and current status of these aquifers, and quantify their resilience/vulnerability to current and future seawater intrusion forcings. We identify two different critical limits of seawater intrusion under groundwater exploitation and/or climatic stress: a limit of well intrusion, at which intruded seawater reaches key locations of groundwater pumping, and a tipping point of complete seawater intrusion up to the prevailing groundwater divide of a coastal aquifer. Either limit can be reached, and ultimately crossed, under intensive aquifer exploitation and/or climate-driven change. We show that seawater intrusion vulnerability for different aquifer cases can be directly compared in terms of normalized intrusion performance curves. The site-specific assessments show that (a) the intruding seawater currently seriously threatens the Nile Delta aquifer, (b) in the Israel Coastal aquifer the sharp interface toe approaches the well location and (c) the Cyprus Akrotiri aquifer is currently somewhat less threatened by increased seawater intrusion.

Seawater intrusion vulnerability indicators for freshwater lenses in strip islands

Freshwater lenses on small islands are some of the most vulnerable aquifer systems in the world. However, there is currently little guidance on methods for rapidly assessing the vulnerability of freshwater lenses to the potential effects of climate change. We address this gap using a simple steady-state analytic modelling approach to develop seawater intrusion (SWI) vulnerability indicator equations, which quantify the propensity for SWI to occur in strip islands due to recharge change and sea-level rise (SLR) (incorporating the effect of land surface inundation (LSI)). The following inferences about SWI vulnerability in freshwater lenses can be made from the analysis: (1) SWI vulnerability indicators for SLR (under flux-controlled conditions) are proportional to lens thickness (or volume) and the rate of LSI and inversely proportional to island width; (2) SWI vulnerability indicators for recharge change (under flux-controlled conditions) are proportional to lens thickness (or volume) and inversely proportional to recharge; and (3) SLR has greater impact under head-controlled conditions rather than flux-controlled conditions, whereas the opposite is the case for LSI and recharge change. Example applications to several case studies illustrate use of the method for rapidly ranking lenses according to vulnerability, thereby allowing for prioritisation of areas where further and more detailed SWI investigations may be required.

Analytical single-potential, sharp-interface solutions for regional seawater intrusion in sloping unconfined coastal aquifers, with pumping and recharge

Summary Contamination of groundwater by intruding seawater is a major problem in many parts of the world. This work derives novel analytical solutions for addressing this problem by extending the Girinskii–Strack concept of discharge potential to represent regional, steady-state, sharp-interface seawater intrusion in a sloping unconfined coastal aquifer. The aquifer has hydraulic conductivity K, is recharged uniformly at the rate r, receives an inflow at its land boundary and has a collector trough (or well gallery idealised as line sink) located at the distance lw from the coastline that penetrates the aquifer and draws groundwater at the rate qw. The theory rests on the approximation of a linearised gravity-part of the hydraulic potential. Analytical solutions for the discharge potential are derived, through which the hydraulic head, the flow depth and the sharp interface, and particularly the location of the interface toe, lT, are also determined. These solutions simplify to known results for the horizontal aquifer case. The utility (and robustness to uncertainty regarding the base slope) of the results in applications is demonstrated in the regional example of the Akrotiri Coastal Aquifer, Cyprus. Recasting the problem in non-dimensional form provides a relationship for the dependence of the relative interface toe location lT/lw on the appropriately normalised difference between the groundwater flow just up-gradient of the collector trough, qo, and the pumping rate, qw, given values of the base slope, r/K and Hsea/lw, where Hsea is the sea-surface elevation above the aquifer base at the coastline. That relationship frames a common groundwater management problem in coastal aquifers subject to a certain exploitation scheme, with lT as decision variable. In an exploratory demonstration study, non-dimensional sets of performance curves are calculated for the regional Akrotiri aquifer. In general, the derived analytical solutions can be used for first-order assessments of seawater intrusion vulnerability and management possibilities across a wide range of current regional coastal aquifer conditions and/or projected water demand, groundwater management and climatic change scenarios.

Vulnerability Indicators of Sea Water Intrusion

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.