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Analytical single-potential, sharp-interface solutions for regional seawater intrusion in sloping unconfined coastal aquifers, with pumping and recharge
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. National Observatory of Athens, Greece.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2012 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 416, 1-11 p.Article in journal (Refereed) Published
Abstract [en]

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 I-w from the coastline that penetrates the aquifer and draws groundwater at the rate q(w). 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, l(T), 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 l(T)/l(w) on the appropriately normalised difference between the groundwater flow just up-gradient of the collector trough, q(o), and the pumping rate, q(w), given values of the base slope, r/K and H-sea/l(w), where H-sea 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 l(T) 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.

Place, publisher, year, edition, pages
2012. Vol. 416, 1-11 p.
Keyword [en]
Seawater intrusion, Sharp interface, Unconfined coastal aquifer, Aquifer sloping, Discharge potential, Groundwater management
National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-76321DOI: 10.1016/j.jhydrol.2011.11.012ISI: 000300755300001OAI: oai:DiVA.org:su-76321DiVA: diva2:526883
Note

3

Available from: 2012-05-15 Created: 2012-05-10 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Seawater intrusion risks and controls for safe use of coastal groundwater under multiple change pressures
Open this publication in new window or tab >>Seawater intrusion risks and controls for safe use of coastal groundwater under multiple change pressures
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the era of intense pressures on water resources, the loss of groundwater by increased seawater intrusion (SWI), driven by climate, sea level and landscape changes, may be critical for many people living in commonly populous coastal regions. Analytical solutions have been derived here for interface flow in coastal aquifers, which allow for simple quantification of SWI under extended conditions from previously available such solutions and are suitable for first-order regional vulnerability assessment and mapping of the implications of climate- and landscape-driven change scenarios and related comparisons across various coastal world regions. Specifically, the derived solutions can account for the hydraulically significant aquifer bed slope in quantifying the toe location of a fresh-seawater sharp interface in the present assessments of vulnerability and safe exploitation of regional coastal groundwater. 

Results show high nonlinearity of SWI responses to hydro-climatic and groundwater pumping changes on the landside and sea level rise on the marine side, implying thresholds, or tipping points, which, if crossed, may lead abruptly to major SWI of the aquifer. Critical limits of coastal groundwater change and exploitation have been identified and quantified in direct relation to prevailing local-regional conditions and stresses, defining a safe operating space for the human use of coastal groundwater. Generally, to control SWI, coastal aquifer management should focus on adequate fresh groundwater discharge to the sea, rather than on maintaining a certain hydraulic head at some aquifer location. First-order vulnerability assessments for regional Mediterranean aquifers of the Nile Delta Aquifer, the Israel Coastal Aquifer  and the Cyprus Akrotiri Aquifer show that in particular the first is seriously threatened by advancing seawater. Safe operating spaces determined for the latter two show that the current pumping schemes are not sustainable under declining recharge.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2014. 36 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 42
Keyword
seawater intrusion, coastal aquifer, tipping points, safe operating space, analytical solution
National Category
Oceanography, Hydrology, Water Resources
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-103137 (URN)978-91-7447-907-2 (ISBN)
Public defence
2014-06-12, Högbomsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

The thesis was founded by two research programmes: NEO private-academic sector partnership and Ekoklim, a strategic governmental funding through Stockholm University

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

 

Available from: 2014-05-22 Created: 2014-05-06 Last updated: 2014-06-16Bibliographically approved

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