Analysis and Remediation of the Salinized, Damour Coastal (Dolomitic) Limestone Aquifer in Lebanon • PhD thesis

Coastal aquifer management has recently emerged as a main scope in groundwater hydrology, especially in arid and semi-arid zones. About two thirds of the human population are currently gathered close to shorelines relying on coastal groundwater resources. Worldwide, these systems are subject to quality deterioration due to a multitude of anthropogenic impacts and subsequent saltwater intrusion (SWI). Many hydrological and hydrochemical features of SWI have been disclosed during the past century through numerous case studies, column studies, scale models, flow and reactive transport modeling. Yet, many scientific and engineering challenges remain, some of which need to be addressed for a better prospecting of future coastal freshwater reserves. The PhD thesis of Wisam Khadra describes and in-depth study.

2017.11.22 Damour PhD KhadraThe scope of the thesis is to contribute to the analysis and remediation of SWI by studying the following aspects:

  1. Response of carbonate aquifers with varying Ca/Mg content to SWI,
  2. Behavior of trace elements (TEs) where fresh and intruded seawater mix,
  3. Derivation of groundwater baseline levels in polluted settings, notably salinized aquifers,
  4. Identification and quantification of major hydrogeochemical processes stimulated by SWI,
  5. Reliability of complex models (especially in karst) with variable-density and solute transport formulations, and
  6. Feasibility of SWI mitigation strategies.

A structured multifaceted approach to analyze and manage SWI in coastal aquifers from detection to remediation is then provided. It was expanded based on the overall outcome of this research. The proposed tools and methods were successfully applied to a stressed dolomitic limestone aquifer system in Lebanon (Eastern Mediterranean), suffering from salinization and other minor anthropogenic impacts, such as inputs from sewage effluents and agricultural processes. The potential of managed aquifer recharge (MAR) and in particular river bank filtration (RBF) is explored as well, for Lebanon in broad lines, and for the study area, as a karst example.

Various tools or methods to analyze SWI in coastal aquifers have been successfully applied in this thesis, such as: the HydroChemical System Analysis for mapping water quality, PHREEQC-2 for 1-D reactive transport modeling, and SEAWAT for density dependent groundwater flow modeling. Other existing tools have been adapted and new tools developed to: derive baseline groundwater conditions, assess the mobilization of chemical constituents under mixing conditions, simulate SWI in poorly karstified aquifers, and mitigate SWI in settings where a precise understanding of system dynamics is not possible, as in karstic or fractured aquifers. All together, they offer an interesting toolbox for investigating SWI anywhere.

In Lebanon as a particular case, more options of water buffering are urgently required. River bank filtration forms a forgotten but strong candidate of managed aquifer recharge (MAR) application to be added to the Lebanese national water strategy. Aquifer storage and recovery (ASR) in alluvial aquifers having nearby recharge sources (e.g. from rivers) also seem to be an attractive option. In addition, further research is needed to investigate the feasibility of utilizing other sources for recharge, for instance by harvesting rainwater, urban stormwater, or even treated effluent water, where rivers are far away or have a too bad water quality.


acrobat icon Analysis and Remediation of the Salinized, Damour Coastal (Dolomitic) Limestone Aquifer in Lebanon