Managed aquifer recharge with reverse-osmosis desalinated seawater: modeling the spreading in groundwater using stable water isotopes

Yonatan Ganot,Noam Weisbrod,Yoram Katz,Ran Holtzman,Anat Bernstein,Daniel Kurtzman,Hagar Siebner

doi:10.5194/hess-22-6323-2018

Abstract

Abstract. The spreading of reverse-osmosis desalinated seawater (DSW) in the Israeli coastal aquifer was studied using groundwater modeling and stable water isotopes as tracers. The DSW produced at the Hadera seawater reverse-osmosis (SWRO) desalination plant is recharged into the aquifer through an infiltration pond at the managed aquifer recharge (MAR) site of Menashe, Israel. The distinct difference in isotope composition between DSW (δ18O = 1.41 ‰; δ2H = 11.34 ‰) and the natural groundwater (δ18O = −4.48 ‰ to −5.43 ‰; δ2H = −18.41 ‰ to −22.68 ‰) makes the water isotopes preferable for use as a tracer compared to widely used chemical tracers, such as chloride. Moreover, this distinct difference can be used to simplify the system to a binary mixture of two end-members: desalinated seawater and groundwater. This approach is validated through a sensitivity analysis, and it is especially robust when spatial data of stable water isotopes in the aquifer are scarce. A calibrated groundwater flow and transport model was used to predict the DSW plume distribution in the aquifer after 50 years of MAR with DSW. The results suggest that after 50 years, 94 % of the recharged DSW was recovered by the production wells at the Menashe MAR site. The presented methodology is useful for predicting the distribution of reverse-osmosis desalinated seawater in various downstream groundwater systems.

Highlights

Desalinated seawater global production is projected to double by 2040 while extending its geographical extent (Hanasaki et al, 2016)
The distinct difference between the water isotopes of the production wells and desalinated seawater (DSW) is shown in a δ2H vs. δ18O diagram for the period of 2015 to 2017 (Fig. 3a and Table S1 in the Supplement)
The chloride concentration of DSW at the Menashe managed aquifer recharge (MAR) site is always lower than 10 mg L−1 (Ganot et al, 2018), while in the local GW it is found in a wider range of 40 to 140 mg L−1

Summary

Introduction

Desalinated seawater global production is projected to double by 2040 while extending its geographical extent (Hanasaki et al, 2016). In Israel, for example, DSW reached 66 % of the domestic and industrial fresh water supply in 2017 (Israel Water Authority, 2018). This growing use of DSW affects downstream water systems such as reservoirs (RonenEliraz et al, 2017; Negev et al, 2017; Stuyfzand et al, 2017; Ganot et al, 2017, 2018), wastewater treatment plants (Lahav et al, 2010; Negev et al, 2017) and agricultural irrigation (Lahav et al, 2010; Yermiyahu et al, 2007). While the relatively rapid hydrological and geochemical processes (timescales of hours to weeks) of this new Published by Copernicus Publications on behalf of the European Geosciences Union

Methods

Results

Conclusion