article · Journal of Hydrology
Groundwater salinisation in coastal aquifers is frequently blamed entirely on seawater intrusion, even though other salinisation sources and pollutants can also be responsible. Evaluating 1,662 groundwater samples from five Mediterranean coastal aquifers demonstrated that chloride serves as a reliable non-reactive tracer to separate contemporary seawater mixing from other sources. By using trend analyses on cumulative probability plots, a specific chloride concentration threshold of 200 milligrams per litre was identified to mark the onset of seawater intrusion. Total dissolved solids, by contrast, proved to be a reactive and less dependable indicator on its own, as elevated levels in freshwater often reflect non-chloride salts or broader pollution. Above the 200 milligrams per litre threshold, groundwater data reveals mixed salinisation sources, distinct saline fluids, and water-rock interactions, providing a structured categorisation to improve coastal aquifer monitoring and water management.
Coastal communities rely on fresh groundwater, but managing supplies requires knowing whether rising salinity stems from seawater encroachment or other contaminants. Establishing a definitive chloride threshold of 200 milligrams per litre prevents misdiagnosing pollution as marine intrusion. This helps water authorities protect coastal aquifers with appropriate remediation measures rather than relying on flawed single indicators like total dissolved solids.
The established threshold and categorisation method offer coastal water authorities, environmental monitoring agencies, and hydrogeological consultancies a tested diagnostic framework for groundwater assessment. While proven on Mediterranean dataset samples, application in operational water quality testing and compliance management appears near-market for testing protocols, though the abstract describes it primarily as a benchmark method rather than a commercial product or software tool.
AI-generated from the published abstract. Always read the original work before citing.
• Polymodal cumulative probability plots mark salinization sources as straight lines. • The chloride threshold of 200 mg/L marks the onset of seawater intrusion. • Results cautions on placing much trust in TDS as single seawater intrusion indicator. • Elevated TDS in freshwater indicate groundwater pollution or non-chloride salt inputs. Seawater intrusion is the primary cause of groundwater salinisation in coastal aquifers. However, attributing salinisation solely to seawater intrusion may not always be accurate, given the likely presence of other sources. To understand if salinisation comes from seawater intrusion and its onset is crucial for groundwater management, but there are no definite threshold values for common indicators such as chlorides. Based on 1662 groundwater analyses from five Mediterranean coastal aquifers, the study aimed to distinguish the effects of mixing with present-day seawater from those caused by other sources. The trend analysis of cumulative probability plots of chloride (and total dissolved solids) is a key method for discriminating different groundwater salinisation sources and processes. Results establish that chloride, as a non-reactive tracer, is a more reliable indicator of seawater intrusion than total dissolved solids, a reactive indicator. A chloride concentration threshold of 200 mg/L identifies the seawater intrusion onset. The threshold validation comes from groundwater salinisation facies, as provided by groundwater-type codification. Fresh groundwater (Cl < 200 mg/L) anomalous total dissolved solids highlight the input of non-chloride salts and pollutants, providing caution regarding using total dissolved solids to recognise seawater intrusion. Beyond the threshold (Cl > 200 mg/L), data disclose emergent signals of salinisation sources and water–rock interaction processes overlapping seawater intrusion or the involvement of saline fluids different from present-day seawater. The threshold and a new categorisation of groundwater in coastal aquifers according to salinisation processes provide a benchmark for identifying and managing seawater intrusion in the Mediterranean area.
This page summarises published work. The authoritative version sits with the publisher.
DOI: 10.1016/j.jhydrol.2025.132775
Is something wrong with this record? Report it or request removal.
Discussion
Have you built on this work, tried to replicate it, or seen it applied in practice? Share what you know. Verified researchers and MARATTO™ domain experts can open a discussion, and any member can reply. Contributions are reviewed before they appear.
No discussion yet. Open the first thread.
New to MARATTO™? Create a free account.
