Combined time‐series resistivity and geochemical tracer techniques to examine submarine groundwater discharge at Dor Beach, Israel

TLDR

The study conducted a high‑resolution stationary geophysical and geochemical survey at Dor Beach, Israel, to investigate how shallow coastal hydrogeology controls submarine groundwater exchange with the Mediterranean Sea. Time‑series resistivity profiles from a new 56‑electrode marine cable, combined with pore‑water salinity and formation resistivity data, mapped the fresh‑water/salt‑water interface and its tidal response to quantify submarine groundwater discharge rates. 222Rn measurements modeled with the resistivity data yielded SGD rates of 0–30 cm day⁻¹ (mean 7.1 cm day⁻¹), indicating a favorable hydrogeologic framework for substantial discharge, with extrapolation suggesting ~7.1 m³ day⁻¹ per m shoreline from a mix of upland fresh groundwater and recycled seawater.

Abstract

A high‐resolution, stationary geophysical and geochemical survey was conducted at Dor Beach, Israel, to examine the shallow coastal hydrogeology and its control on the exchange of submarine groundwater with the shallow Mediterranean Sea. Time‐series resistivity profiles using a new 56 electrode (112‐m long) marine cable produced detailed profiles of the fresh water/salt water interface and the subtle response of this interface to tidal excursions and other forcing factors. Such information, when ground‐truthed with representative pore water salinities and formation resistivity values, can provide unique information of the extent and rates of submarine groundwater discharge (SGD). Time‐series 222 Rn measurements of the adjacent coastal water column complemented these geophysical techniques and were modeled to yield integrated advective flow rates across the sediment/water interface, which at Dor Beach ranged from about 0 to 30 cm day −1 (mean = 7.1 cm d −1 ), depending on the tidal range. Such results suggest that the underlying hydrogeologic framework at Dor is favorable for substantial SGD. Extrapolating these SGD estimates across a 100‐m wide coastal zone implies that the Rn‐derived SGD rate would equal ∼7.1 m 3 d −1 per m of shoreline, and that the source of this discharging groundwater is a complex mixture of fresh groundwater derived from the upland Kurkar deposits, as well as locally recycled seawater.