Recharging Mechanisms and Seawater Intrusion in Karst Aquifers in Northwest Sri Lanka, Based on Hydrogeochemistry and Water Isotopes

Bandara UGC, Diyabalanage S, Barth J, Chandrajith R (2023)


Publication Type: Journal article

Publication year: 2023

Journal

DOI: 10.1021/acsestwater.2c00454

Abstract

Geochemical and isotope data of karstic aquifer systems in the Mulankavil area in northwest Sri Lanka were investigated to constrain recharging and discharging mechanisms, and possible seawater intrusions. The electrical conductivity (EC) of groundwater was measured in the dry (n = 139) and rainy (n = 78) seasons to assess possible saltwater intrusions, from which 25 wells were selected for detailed geochemical analyses. Water isotope analyses (expressed as delta 2HH2O, delta 18OH2O) were measured in 32 wells for five months. The mean EC of groundwater during both seasons was 2,435 mu S/cm, and higher values from the coastal stretch indicated seawater intrusion. Increasing EC values in the dry period indicated a temporary inland saltwater wedge. High hydraulic gradients with rapidly discharging groundwater partially removed seawater intrusions during the monsoon season. Water isotopes in the region defined an individual evaporation line with delta 2HH2O= 6.69*delta 18OH2O -0.77 (r2 = 0.989), indicating a long enough residence time to allow evaporation before infiltration. Groundwater near sinkhole systems was found to be predominantly of the Ca-Mg-HCO3 type and changes to the Na-Cl type toward the coast. The results of this study revealed conduit systems in the karst subsurface as essential pathways for controlling seawater intrusion.

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APA:

Bandara, U.G.C., Diyabalanage, S., Barth, J., & Chandrajith, R. (2023). Recharging Mechanisms and Seawater Intrusion in Karst Aquifers in Northwest Sri Lanka, Based on Hydrogeochemistry and Water Isotopes. ACS ES&T Water. https://dx.doi.org/10.1021/acsestwater.2c00454

MLA:

Bandara, U. G. Chaminda, et al. "Recharging Mechanisms and Seawater Intrusion in Karst Aquifers in Northwest Sri Lanka, Based on Hydrogeochemistry and Water Isotopes." ACS ES&T Water (2023).

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