Groundwater withdrawal in randomly heterogeneous coastal aquifers

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.

Impacts of the Scale of Representation of Heterogeneity on Simulated Salinity and Saltwater Circulation in Coastal Aquifers

“…Li et al (2016) reported a similar influence of heterogeneity on the mixing zone for a domain of 130 × 6 m and found that heterogeneity significantly affects SGD patterns. Siena and Riva (2018) assessed the role of heterogeneity under pumping operations. Their simulation results suggested that aquifer heterogeneity increases the area of the mixing zone and slows the intrusion process.…”

A Semianalytical Method to Fast Delineate Seawater‐Freshwater Interface in Two‐Dimensional Heterogeneous Coastal Aquifers

“…Bear et al (2001) performed a 3-D numerical simulation of the heterogeneous coastal aquifer in Israel. Held et al (2005) investigated the effect of 2-D heterogeneity in the Henry Problem and found using numerical simulations that heterogeneity results in a reduction in the extent of SWI and widening of the mixing zone, a phenomenon also observed in previous studies (e.g., Kerrou & Renard, 2009;Siena & Riva, 2018). Held et al (2005) also proposed geometric mean as the effective permeability for the isotropic case, the same as that in the single-density flow, however, valid only in the case of small-scale heterogeneities.…”

Review: Saltwater intrusion in fractured crystalline bedrock

“…The conceptual model of a sharp interface is still frequently applied, although it does not account for mixing along the interface and therefore simplifies the problem (e.g. Mehdizadeh et al 2017;Siena and Riva 2018). Whereas a sharp interface approximation can be applied under certain conditions (cf.…”

“…Therefore, the validity of a sharp interface applied on real case scenarios is already limited in unconsolidated material (e.g. Reilly and Goodman 1985;Pool and Carrera 2011;Llopis-Albert and Pulido-Velazquez 2014;Siena and Riva 2018). Nevertheless, the application of the sharp interface approximation for sustainable water-resources management is a conservative measure, since it overestimates the frontal extent of the SWI and underestimates critical pumping rates (Pool and Carrera 2011).…”