Water scarcity coefficient (AWARE)

A water scarcity coefficient is an indicator used in water resource management to quantify the pressure that demand places on the water available in a given area. It helps to identify situations of water stress and to guide decisions in planning, agriculture, industry and public policy. The AWARE method (Available WAter REmaining) is the most widely used way of turning this idea into a standardised scarcity factor for environmental footprinting.

Freshwater makes up only around 2.5% of all the water on Earth, and only a small fraction of that is easily accessible. With a large share of the world's population facing water scarcity for at least part of the year, scarcity indicators have become essential tools in environmental and socio-economic assessments.

The basic scarcity coefficient

In its simplest form, a scarcity coefficient is expressed as the ratio between the volume of water demanded and the volume of water available in a given area and period. A common interpretation of the withdrawal-to-availability ratio is:

• Below 0.2: relative abundance, low pressure.
• 0.2 to 0.4: emerging water stress.
• 0.4 to 0.8: medium to high water stress.
• Above 0.8: severe or critical scarcity.

This kind of ratio is the basis of well-known indicators such as the Water Stress Index (WSI), while the Falkenmark indicator instead measures cubic metres of water available per person per year.

The AWARE method

AWARE is the consensus characterisation model developed by the WULCA working group (under the UNEP Life Cycle Initiative) to assess water scarcity in life cycle assessment. Instead of a simple demand/availability ratio, AWARE is based on the water remaining in an area once the needs of humans and ecosystems have been met, and answers the question: what is the potential to deprive another user, human or ecosystem, when consuming a cubic metre of water here?

• The AWARE characterisation factor is dimensionless and ranges from 0.1 to 100, normalised against the world average.
• A value of 1 represents the world average; values above 1 indicate basins with higher-than-average scarcity, and values below 1 relative abundance.
• Results are reported in cubic metres of world equivalent (m3 world-eq), making water footprints comparable across regions.

For the application of AWARE as a footprint indicator, see Water Scarcity Footprint (AWARE) and the AWARE entry.

Variables used

To estimate scarcity, the following are typically considered:

• Water availability: surface flows, aquifer recharge and reservoir storage.
• Agricultural demand: crop irrigation and livestock.
• Industrial demand: production processes and energy.
• Urban demand: domestic consumption and services.
• Climatic factors: droughts and extreme rainfall.

Why scarcity coefficients matter

1. Environmental diagnosis: they measure how sustainable water use is in a territory.
2. Water planning: they help prioritise critical river basins.
3. Business management: they support assessment of water risk in operations and supply chains.
4. Climate adaptation: they identify areas vulnerable to prolonged droughts.

The situation in Spain

Spain is one of the European countries with the highest water scarcity. Several Mediterranean basins, such as the Segura, Júcar and Guadiana, regularly experience very high water stress, with demand in some periods approaching or exceeding the renewable resources available, while basins in the north of the country generally have more water available per inhabitant. The exact values vary year to year and depend on the methodology used, so they should be read as indicative rather than fixed figures.

Related regulation

• EU Water Framework Directive (2000/60/EC): the European framework for sustainable water management.
• National Hydrological Plan (Spain) and Law 10/2001, which use scarcity criteria in water planning.
• River basin drought plans drawn up by the river basin authorities.

Practical applications

Agriculture

• Planning crops according to water availability.
• Optimising irrigation to ease pressure in critical areas.

Industry

• Assessing risk for water-intensive plants (food, textiles, energy).
• Designing wastewater reuse systems.

Public policy

• Setting consumption restrictions during droughts.
• Prioritising human supply over industrial or agricultural uses.

Limitations

1. It does not capture water quality: polluted water that is technically available is not usable.
2. Temporal variability: an annual value can hide seasonal droughts.
3. Efficiency: a simple coefficient does not reflect network losses or irrigation inefficiencies.

Links to the circular economy

Scarcity coefficients encourage companies and governments to apply circular economy measures to water, such as reusing wastewater, improving efficiency in agricultural and industrial processes, and designing less water-intensive products.

At Manglai we help companies measure their water footprint and assess water-related risk across their operations and value chain. Discover how Manglai can help you.