Journal Article

Influences of seawater intrusion and anthropogenic activities on shallow coastal aquifers in Sri Lanka: evidence from hydrogeochemical and stable isotope data

Jayathunga, Kaushalya, Chandrajith, Rohana, Diyabalanage, Saranga, Frank, Alexander H., Barth, Johannes A. C.

2020

Overview

Water supplies in coastal aquifers throughout the world are often threatened by salinization due to seawater intrusion and anthropogenic activities. In the Kalpitiya Peninsula in Sri Lanka, agricultural and domestic water supplies entirely depend on groundwater resources extracted from unconfined Holocene sandy aquifers. To differentiate the effects of seawater intrusion and agriculture on the coastal aquifers of this 160 km 2 peninsula, 43 groundwater samples were collected. These samples were analyzed for major ions, trace elements, and stable isotopes of water (δ 18 O and δ 2 H). The solute compositions were dominated by Cl − , SO 4 2 − , and HCO 3 − , which were mostly balanced by Ca 2+ , Na + , and Mg 2+ . Among the four main water types, Na + -Cl − and Ca 2+ - SO 4 2 − classifications were predominant in the investigated aquifers. Modifications of the groundwater due to evaporation during irrigation activities, but also due to seawater intrusion seem most plausible as indicated by the correlation of δ 18 O with δ 2 H (δ 2 H = 5.51 * δ 18 O-3.08, r  = 0.93) deviating from the local meteoric water line. Particularly in the southern part of the peninsula, Mg 2+ /Ca 2+ ratios and stable isotopes of water attributed salinization of groundwater to agricultural activities. However, especially in the north, seawater intrusions were also evident. Established mass balance calculations revealed that local groundwater had seawater admixtures of up to 12%. Our results indicate that integrated water management is essential and water resources should critically monitor in the Kalpitiya Peninsula in order to avoid over-exploitation and further seawater inflows.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Agricultural management / Anthropogenic factors / Aquatic Pollution / Aquifers / Atmospheric Protection/Air Quality Control/Air Pollution / Calcium / Calcium ions / Chemical analysis / Coastal aquifers / Coastal waters / Domestic water / Earth and Environmental Science / Ecotoxicology / Environment / Environmental Chemistry / Environmental Health / Environmental science / Evaporation / Groundwater / Holocene / Holocene epoch / Human influences / Hydrogeochemistry / irrigation / Isotopes / Magnesium / Mass balance / Meteoric water / Research Article / Resource management / Saline water intrusion / Salinization / Salt water intrusion / saltwater intrusion / Seawater / solutes / Sri Lanka / Stable isotopes / Trace elements / Waste Water Technology / Water analysis / Water Management / Water Pollution Control / Water resources / Water sampling / Water supply