Abstract
Abstract. We analyze the combined effects of aquifer heterogeneity and pumping operations on seawater intrusion (SWI), a phenomenon which is threatening coastal aquifers worldwide. Our investigation is set within a probabilistic framework and relies on a numerical Monte Carlo approach targeting transient variable-density flow and solute transport in a three-dimensional randomly heterogeneous porous domain. The geological setting is patterned after the Argentona river basin, in the Maresme region of Catalonia (Spain). Our numerical study is concerned with exploring the effects of (a) random heterogeneity of the domain on SWI in combination with (b) a variety of groundwater withdrawal schemes. The latter have been designed by varying the screen location along the vertical direction and the distance of the wellbore from the coastline and from the location of the freshwater–saltwater mixing zone which is in place prior to pumping. For each random realization of the aquifer permeability field and for each pumping scheme, a quantitative depiction of SWI phenomena is inferred from an original set of metrics characterizing (a) the inland penetration of the saltwater wedge and (b) the width of the mixing zone across the whole three-dimensional system. Our results indicate that the stochastic nature of the system heterogeneity significantly affects the statistical description of the main features of the seawater wedge either in the presence or in the absence of pumping, yielding a general reduction of toe penetration and an increase of the width of the mixing zone. Simultaneous extraction of fresh and saltwater from two screens along the same wellbore located, prior to pumping, within the freshwater–saltwater mixing zone is effective in limiting SWI in the context of groundwater resources exploitation.
Highlights
Groundwater resources in coastal aquifers are seriously threatened by seawater intrusion (SWI), which can deteriorate the quality of freshwater aquifers, limiting their potential use
The effects of heterogeneity on SWI are inferred by comparing the results of our Monte Carlo (MC) simulations against those obtained for an equivalent homogeneous aquifer, characterized by an effective permeability, kef
The latter is here evaluated as kef = e Y +σY2/6 = 2.09 × 10−11 m2 (Ababou, 1996)
Summary
Groundwater resources in coastal aquifers are seriously threatened by seawater intrusion (SWI), which can deteriorate the quality of freshwater aquifers, limiting their potential use. The development of effective strategies for sustainable use of groundwater resources in coastal regions should be based on a comprehensive understanding of SWI phenomena This challenging problem has been originally studied by assuming a static equilibrium between freshwater (FW) and seawater (SW) and a sharp FW–SW interface, where FW and SW are considered as immiscible fluids. The vertical position of the FW–SW interface below the sea level, z, is given by the Ghyben–Herzberg solution, z = hFρF/ ρ, where hF is the FW head above sea level and ρ = ρS − ρF is the density contrast, ρS and ρF, respectively, being SW and FW density Starting from these works, several analytical and semi-analytical expressions have been developed to describe SWI under diverse flow configurations (e.g., Strack, 1976; Dagan and Zeitoun, 1998; Bruggeman, 1999; Cheng et al, 2000; Bakker, 2006; Nordbotten and Celia, 2006; Park et al, 2009). All of these sharp-interfacebased solutions neglect a key aspect of SWI phenomena, i.e., Published by Copernicus Publications on behalf of the European Geosciences Union
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
