Aquifer Response to Estuarine Stream Dynamics

Yehuda Shalem,Barak Herut,Yoseph Yechieli,Yishai Weinstein

doi:10.3390/w11081678

Abstract

While seawater intrusions are widely discussed, the salinization of coastal aquifers via narrow rivers is hardly documented. This study investigates groundwater dynamics in an aquifer next to an estuarine stream on the eastern Mediterranean coast. Groundwater levels and salinization patterns were examined as a response to dynamic changes in estuary water, both in low-and high-permeability aquifer units. In the high-permeability unit, the extent of salinization was relatively constant, reaching a distance of at least 80 m from the river, with no long-term changes in fresh-saline interface depth, indicating that the system is in a quasi-steady state. Groundwater salinity in the low-permeability unit showed frequent and large fluctuations (up to 36 and 22 at 5 and 20 m from the river, respectively). We suggest that the river may have a more immediate impact on a low-permeability than on a high-permeability aquifer. This is dependent on the history of seawater encroachments to the river, which are better preserved in the low-permeability unit, and on the hydrogeology of this unit, where sand lenses can serve as high-permeability conduits. However, this unit can efficiently prevent a large extent of salinization of the regional coastal aquifer by the estuary water.

Highlights

Groundwater is an essential freshwater resource in many coastal areas
The problem of seawater intrusion into coastal aquifers is widely recognized for its importance with regard to water resource management and planning in coastal areas [10,12,13]
We investigate the dynamics and mechanisms of aquifer salinization next to a bar-built estuarine river by integrating high-resolution level and salinity measurements in the river and the adjacent aquifer

Summary

Introduction

Groundwater is an essential freshwater resource in many coastal areas. Optimal management of coastal aquifers is becoming increasingly important due to population growth and climate change, which potentially affects water quality, ecosystem health and diversity, and water-supply reliability [1,2,3,4,5].Surface water and groundwater are intrinsically linked systems [6,7,8,9]. Groundwater is an essential freshwater resource in many coastal areas. Optimal management of coastal aquifers is becoming increasingly important due to population growth and climate change, which potentially affects water quality, ecosystem health and diversity, and water-supply reliability [1,2,3,4,5]. Rivers, lakes and coastal environments represent zones of interaction and transition between the two systems, where dissolved constituents such as pollutants can be diluted, exchanged, transformed, or degraded. The problem of seawater intrusion into coastal aquifers is widely recognized for its importance with regard to water resource management and planning in coastal areas [10,12,13]. The extent of seawater intrusion into the coastal aquifer can be estimated by salinity measurements in observation wells [14,15,16,17,18] or by hydrological modeling [15,19,20,21,22], as well as by geophysical measurements [14,23,24]

Methods

Results

Discussion

Conclusion