Drought risk (Aqueduct 4.0)
This layer indicates where droughts are likely to occur and where their consequences are likely to be most severe.
Source: WRI Aqueduct 4.0 Year: 2023 Category: Physical risks · Provisioning services · Water availability Coverage: Global Format: Boundary polygons (sub-national assessment units) Used in risk analysis: No (contextual layer; not used in materiality scoring)
What it shows
This layer indicates where droughts are likely to occur and where their consequences are likely to be most severe. It brings together the chance of drought with the people and assets that would be exposed and how vulnerable they are, giving a single screening signal for water-scarcity risk to operations, supply chains and surrounding ecosystems.
How it is built
The indicator comes from the World Resources Institute's Aqueduct global water-risk framework. Drought risk combines three elements: the likelihood that droughts occur in a given area, the population and assets exposed to them, and the vulnerability of that population and those assets to the resulting adverse effects. These are integrated into a single composite risk value reported for each assessment unit.
How to read it
Higher values indicate a higher risk of drought — a combination of greater drought likelihood, more exposure and greater vulnerability. Lower values indicate limited drought risk. As values are reported per polygon, a site located within a high-value unit should be treated as drought-exposed and examined further.
Class thresholds
The underlying quantity is a composite drought-risk index — a dimensionless score on a 0–1 scale (drr_cat) that combines drought likelihood, exposed population and assets, and vulnerability into one value per assessment unit. The mapped categories map to the following thresholds on that score:
| Class | Drought-risk score (0–1) |
|---|---|
| No Risk | 0 |
| Low | 0.0 – 0.2 |
| Medium | 0.2 – 0.4 |
| High | 0.4 – 0.6 |
| Extremely High | 0.6 – 0.8 |
This layer is contextual and is not used in materiality scoring, so it carries no risk-flag threshold of its own.
How these thresholds were set. The score and its five-class split follow the WRI Aqueduct drought-risk methodology; the even 0.2-wide bins on the 0–1 composite are Aqueduct's own convention rather than a Darwin construction. The exact derivation is set in the Aqueduct methodology and is not re-documented here.
Reference: WRI Aqueduct — wri.org/aqueduct.
Source
Aqueduct (World Resources Institute). WRI Aqueduct global water-risk framework — https://doi.org/10.46830/writn.23.00061.
Comparison with the WWF Risk Filter Suite
This is a direct equivalent of the WWF Water Risk Filter B2 Drought category. Both rely on the same Aqueduct drought-risk family, so the two are closely aligned.
Legend
Symbolised field: Drought risk category
| Value (Drought risk category) | Label | Colour |
|---|---|---|
| -1 | No Data | #d3d3d3 |
| 0 | No Risk | #74afd1 |
| 1 | Low Risk (0.0-0.2) | #aac7d8 |
| 2 | Medium Risk (0.2-0.4) | #dededd |
| 3 | High Risk (0.4-0.6) | #f8ab95 |
| 4 | Extremely High Risk (0.6-0.8) | #f27454 |
Generated from darwin/layers/layer-drought-risk-aqueduct-4-0.toml and risk_indicator_pairs.toml (develop).