Water Purification Contamination Index

Source: Hou et al. 2025, Tang et al. 2021, PFAS Data Hub, Le Monde / ADES, HydroSHEDS Year: 2015-2023 Category: Physical risks · Enabling services · Water condition Coverage: World (HydroSHEDS 30″ tiles). PFAS data covers Europe only. Format: Raster grid (COG), on the HydroSHEDS 30″ network Used in risk analysis: Yes. It drives the contamination aggravation of the Water Purification Loss layers in Resilience. It is not a Sites & territories materiality flag.

What it shows

This layer estimates how likely the water a place drains into is contaminated today. It reads three contaminant families: soil toxic metals, pesticides and PFAS. The value is the probability, from 0 to 1, that at least one of them exceeds its threshold. It has no trajectory: it is a baseline state.

How it is built

Each family gives a probability p of exceeding its threshold:

• Soil toxic metals: Hou et al. (2025), human-health threshold, worst metal.
• Pesticides: Tang et al. (2021), fitted to the share of French groundwater stations with a pesticide exceedance over 2016-2023. That share comes from Le Monde, "300 contaminants dans nos nappes" (2024), built from ADES.
• PFAS: the PFAS Data Hub, as the share of water points within 25 km where the sum of 20 PFAS reaches 100 ng/L or more. Every year of the hub is used, keeping the most recent year per location. Where no water point is within reach, the layer uses 0.050, the European mean over the cells that have a value.

The three combine as P = 1 − Π(1 − p). P is then averaged over the upstream area on the HydroSHEDS 30″ river network. A cell off the river network reads the river it drains into.

How to read it

A higher value means a higher chance that the water reaching the place exceeds a contamination threshold. Keep two limits in mind. PFAS is measured in Europe only. Elsewhere PFAS reads the European mean, not zero, so a cell outside Europe carries a PFAS term that was not measured there. The pesticide fit is made on French groundwater stations.

The Water Purification Data Coverage layer shows where PFAS is measured and where it is filled. The Loss of water purification page explains how Resilience adds this contamination term to the river-nitrogen loss.

Source

Hou et al. (2025), Science; Tang et al. (2021), Nature Geoscience; PFAS Data Hub (CNRS, 2026); Le Monde (2024), "300 contaminants dans nos nappes", data.gouv.fr, from ADES; HydroSHEDS (Lehner & Grill 2013). The licences of Hou et al., Tang et al., the PFAS Data Hub and Le Monde / ADES are not confirmed. HydroSHEDS is used under the HydroSHEDS v1 licence (WWF); its required statement is on the Loss of water purification page.

Legend

Symbolised field: Contamination index (0–1)

Generated from darwin/layers/layer-water-purification-contamination-index-europe.toml (develop).