National Water Security Index (NWSI)

The National Water Security Index (NWSI) is a composite indicator that measures how well a country can guarantee enough water of acceptable quality at an affordable cost, while limiting the risks linked to droughts, floods and pollution and protecting freshwater ecosystems. It is the headline metric of the Asian Water Development Outlook (AWDO), a flagship assessment published by the Asian Development Bank (ADB) in partnership with UNEP-DHI and other institutions.

The NWSI is used to compare countries, prioritise investment and track progress toward Sustainable Development Goal 6 (clean water and sanitation). The most recent edition, AWDO 2025, assessed 50 economies across Asia and the Pacific.

How the NWSI is structured

The index is built from five Key Dimensions (KDs), each scored out of 20, giving a maximum total score of 100:

• KD1 (Rural household water security): safe, reliable and climate-resilient drinking water and sanitation in rural areas.
• KD2 (Economic water security): water to support agriculture, industry and energy production.
• KD3 (Urban water security): water supply, sanitation and drainage in towns and cities.
• KD4 (Environmental water security): the health of rivers and freshwater ecosystems.
• KD5 (Water-related disaster security): resilience to floods, droughts and storms.

Each dimension is placed on a five-step scale: Nascent, Engaged, Capable, Effective and Model. A guiding principle of the framework is that a country's water security is only as strong as its weakest link, so the overall classification is driven by the lowest-scoring dimension rather than the simple average.

How to read the score

A higher NWSI signals stronger water security. Low scores point to gaps that expose households, the economy and ecosystems to water stress, unreliable supply or disaster risk. Because the five dimensions are reported separately, the NWSI also shows where a country needs to act, not just how it ranks overall.

The OECD water security framework

The NWSI is sometimes confused with the OECD's water security work, which is a separate but complementary approach. The OECD frames water security around the management of four interrelated risks: shortage (too little water), inadequate quality (water unfit for use), excess (floods and destructive accumulation) and the risk of undermining the resilience of freshwater systems. Both approaches share the same goal of moving from a crisis response to proactive, risk-based water management.

Why the NWSI matters for organisations

National water security shapes the operating environment for any water-dependent business. Companies use indices such as the NWSI, alongside the WRI Aqueduct Water Risk Atlas, to:

• Screen the water risk of countries and regions when siting plants or sourcing materials.
• Inform a corporate water risk assessment and resilience planning.
• Set context-based water targets and pursue water neutrality or replenishment goals in stressed basins.

Related indicators

• AWARE: a scarcity characterisation factor used in water footprinting that complements national-level indices at the river-basin scale.
• Water footprint: measures the volume of freshwater consumed and polluted by an activity, product or organisation.
• Water resilience: the capacity of a system to absorb and recover from water-related shocks, central to KD5.

Limitations and future developments

• Data availability and consistency vary across countries, especially for water quality, which can affect comparability.
• Aggregating complex realities into a single score can mask important sub-national differences between regions or between cities and rural areas.
• Successive AWDO editions refine the methodology and expand the indicators behind each dimension, so scores are most useful when read as trends rather than absolute values.

The NWSI condenses the complexity of water security into a comparable score, acting as a compass for public investment and policy. For companies, it is a useful entry point for understanding the water context of the territories where they operate. At Manglai we help companies measure their environmental footprint and prepare their sustainability reporting, including water-related risks. Discover how Manglai can help you.