Intrusion transect
Mean Cl-based seawater fraction per well versus distance from coast. Bubble size reflects number of measurements. The Cl-based f_sw is the physically correct tracer (conservative, no cation exchange artifacts).
Each point = one well (mean across all Cl observations). Reference: Appelo & Postma (2005); Werner et al. (2013).
Time series
Cl-based seawater fraction over time for a selected well. Points are coloured by contamination class.
Depth profiles
Cl-based seawater fraction vs sampling depth for all wells in the selected year.
Depth in metres below ground level. Inverted axis.
Cl vs EC diagnostic
Comparison of Cl-based and EC-based seawater fractions. Divergence reveals hydrogeochemical processes beyond simple mixing. Select a well to see its time series below.
f_cl vs f_ec — all observations
Ratio ≈ 0.42 → seawater mixing
Ratio > 0.42 → freshening phase
Cation exchange: Na⁺ released by sediment adsorbs to clay → EC drops while Cl⁻ stays high
Ratio < 0.42 → non-seawater EC source
Elevated EC from anthropogenic input, evaporites, or SO₄²⁻ / HCO₃⁻ enrichment — not from marine intrusion
Divergent observations (>5% diff):
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Reference: Custodio & Bruggeman (1987) UNESCO; Appelo & Postma (2005). Cl/EC ratio for Mediterranean seawater ≈ 0.42 mg·L⁻¹/µS·cm⁻¹.
Wedge estimation
Per-well max and mean Cl-based SW fraction ordered by distance. The 50% isoline marks the Ghyben-Herzberg wedge toe criterion.
Well locations
Spatial distribution coloured by mean Cl-based seawater fraction. Click any marker for details.
ETRS89 UTM 31N → WGS84. Basemap: OpenStreetMap.
System comparison
Ter vs Tordera: key metrics using the Cl-based seawater fraction (Appelo & Postma, 2005).
Cl-based transect — both systems
Cl vs EC fraction — both systems
Tordera shows zero divergent observations between f_cl and f_ec (all |diff| < 0.05), confirming EC is a reliable proxy there. The Ter shows 16 divergent observations, concentrated at near-coast well 17199-0029, revealing active cation exchange cycles linked to seawater intrusion and freshening events.