Water Resilience Index

The Water Resilience Index (WRI) is a composite indicator that quantifies the ability of a system (basin, city, industry, or country) to anticipate, absorb, and recover from water deficits.

Inspired by the approach of Hall et al. (2014) and adapted by the World Bank Water GP (2023), the WRI combines information on supply, demand, storage, source diversification, and governance.

Base formula

WRI = 1 / Σ (Annual deficit²)‍

where annual deficit = Demand – Effective supply, normalised by demand.

The result is normalised between 0 and 1. Interpretation:

• > 0.70 · High resilience
• 0.50–0.69 · Medium resilience
• < 0.50 · Low resilience, high operational risk

Components and recommended weightings

• Per capita availability adjusted by AWARE (30%)
• Storage coverage (20%): days of demand covered by reservoirs and aquifers
• Source diversity (15%): inverse HHI index of each source’s share
• Recovery time (15%): days to restore 95% of service after an event
• Adaptive governance (10%): existence of drought/flood plans and open data
• Water insurance coverage (10%): share of population/GDP covered by parametric insurance

Calculation steps

1. Historical supply and demand series (≥ 20 years)
2. Identification of shocks: droughts, infrastructure failures, floods
3. Calculation of the normalised annual deficit
4. Application of the WRI formula and weightings
5. Validation against hydroclimatic series and operational KPIs

Strategies to improve the WRI

• Grey–green infrastructure: levees plus wetland restoration to retain 10% of flood peaks
• Renewable desalination and indirect potable reuse: adds >25% to source diversification
• Digital twins: anticipate deficits 15 days in advance and reduce losses by 12%
• Water markets and rights banks: flexibility and scarcity reduction of 8–15%
• Tiered tariffs and consumption apps: reduce urban demand by 10–20%
• Parametric insurance: ≥80% coverage of exposed demand mitigates financial risk

Integration with international frameworks

• Sendai Framework: the WRI feeds indicators B & C on losses and damages
• OECD Water Security: complements the four pillars with a quantitative KPI
• National Adaptation Plans: uses the WRI to prioritise investments in critical basins

Limitations and mitigations

• Data gaps: use GRACE satellites for near real-time groundwater storage
• Uneven sectoral coverage: adapt the formula for specific industrial systems
• Non-linear extreme events: apply stochastic models and CMIP6 scenarios

Corporate WRI and finance

• Corporations: plant WRI = 1 / Σ (monthly deficit²) weighted by AWARE
• KPI-linked blue bonds: variable coupon if local WRI increases by ≥0.05
• ESG ratings: MSCI Water Security upgrades one category if verified WRI > 0.70

The Water Resilience Index makes it possible to quantify, compare, and improve the capacity to withstand water shocks. Achieving a WRI > 0.70 requires coordinated investment in infrastructure, nature, governance, and innovative finance, generating socio-economic returns 4–7× higher than the costs.