Water Dependency Index (WDI)

The WDI quantifies what share of a territory’s, sector’s or organisation’s total water footprint is satisfied with imported virtual water—that is, the water embedded in goods and services produced in other basins or countries. A high WDI indicates significant exposure to climatic, regulatory, or geopolitical events occurring outside domestic borders.

Formula and interpretation ranges

WDI (%) = (Imported virtual water / Total water footprint) × 100

• 0–20%: Low dependency
• 21–50%: Moderate dependency
• >50%: High dependency and potential risk

Components of imported water

• Crops and food products: soy, wheat, rice, coffee
• Textile fibres: cotton, viscose
• Minerals and metals: lithium, cobalt, bauxite used in batteries and electronics
• Manufactured products: clothing, smartphones, automobiles

Examples of national WDIs (2024)

• Japan → 78%: depends heavily on cereal imports and livestock fed with Brazilian soy
• Italy → 62%: high consumption of coffee and cocoa; limited domestic water availability in the south
• Brazil → 18%: net exporter of virtual water (grains, meat)
• United Arab Emirates → 92%: almost all food-related water footprint is external

Calculation methodology

1. Inventory of imported goods (customs data, COMTRADE)
2. Assignment of virtual-water coefficients (WaterStat, FAO AquaCrop)
3. Calculation of imported blue, green, and grey water
4. Summation of domestic water footprint (internal production)
5. Application of the WDI formula

Strategic implications

• Food security: a WDI > 60% signals strong vulnerability to droughts or export restrictions in supplier countries
• Displaced environmental footprint: ecological impacts occur far from consumers; reputational risk increases
• Trade and tariff policy: potential introduction of water-related border adjustments (Water CBAM) for water-intensive products

How to reduce the WDI

• Diversify sourcing, avoiding concentration in high-stress basins (AWARE > 20)
• Boost efficient domestic production via precision irrigation and drought-tolerant crops
• Substitute high-water-use products: almond milk → local oat milk
• Resilient procurement contracts with suppliers certified in water stewardship (AWS)
• Cooperation programmes: invest in water efficiency in partner countries to stabilise supply

Integration into corporate ESG reporting

• Report the WDI under water-risk disclosures in CDP Water
• Link WDI-reduction goals with corporate water-neutrality strategies
• Publish annual improvements and mitigation actions in CSRD reports

Limitations and challenges

• Data quality: virtual-water coefficients vary by local farming practices and require periodic updates
• Time lag: annual customs data may hide short-term shocks
• Partial service coverage: virtual water in digital services or tourism is difficult to quantify

Relationship with other indicators

• Footprint Displacement Index (FDI): broadens the scope to other environmental footprints
• Water security: a high WDI reduces national water security
• Water vulnerability: external dependency increases exposure to events beyond domestic control

The Water Dependency Index reveals how consumption is interconnected with distant water resources. A WDI > 50% raises significant challenges for water security and extended environmental responsibility; reducing it through diversification, efficiency, and cooperation is essential to building resilience in a changing climate.