There are different ways to measure how deeply the demand for water exceeds the supply and what it means
Water scarcity and water stress are terms we hear often, but what exactly do they mean? It depends on how they are measured.
Falkenmark Water Stress Indicator
One widely used method of measuring water scarcity is the Falkenmark Water Stress Indicator, also known as the Falkenmark indicator or the water stress index. It defines water scarcity as the total amount of freshwater available to people living in a certain region. It measures water scarcity as the amount of renewable water available per person per year, as follows: When the amount of renewable freshwater in a country is less than 1,700 cubic meters per person per year, the region is considered to be water-stressed; when this falls below 1,000 m3, the region is considered to be experiencing water scarcity; and when the amount of renewable water per person per year drops to less than 500 m3, the region is considered to be experiencing absolute water scarcity.
This method is simple but does have limitations, as it doesn’t take into account seasonal and regional variations in water availability and water use. It also fails to take into account whether the water resources are readily accessible or safe to use for the intended purpose.
The Criticality Ratio, also known as the withdrawal-to-availability ratio, offers an alternative approach. Instead of working on the assumption that countries use equal amounts of water per person, this method defines water scarcity according to a region’s demand versus water supply. It measures water scarcity as the proportion of total water withdrawn annually relative to the total amount of water available. According to this method, a region is considered water-scarce when annual withdrawals fall between 20% and 40% of the available supply, and severely water-scarce when withdrawals exceed 40% of the available water resources.
While this method does account for regional differences in supply and demand, it also has limitations. It doesn’t consider human contributions to the water supply, such as desalination or water recycling and reuse. Nor does it consider human endeavors to reduce consumption, through behavioral changes or water-saving technologies, for example.
Water Accounting Plus (WA+) Framework
To address some of these shortcomings, the International Water Management Institute, in partnership with IHE-Delft Institute for Water Education, developed a measure of water scarcity that takes a more comprehensive approach. Instead of relying on patchy local data, the WA+ framework uses global hydrological models and open-access remote sensing data to analyze water supply and demand in complex river basins. It takes into account water held in human-made water infrastructure, such as desalination plants, as well as recycled water.
Using this method, countries predicted to be unable to meet future water demand without investing in water infrastructure and improving water efficiency are categorized as economically water-scarce, and countries that will be unable to meet future water demand even if infrastructure investments are made are categorized as physically water-scarce.
Water Poverty Index
The Water Poverty Index offers a far more complex approach. It considers the contributions made by income and wealth in determining water scarcity by assessing social, environmental, and economic factors that affect water availability.
Planning for Water Security
The global supply of freshwater remains fairly constant, yet the demand for water is growing significantly. Without planning, water scarcity will become a problem worldwide. Investing in innovative water treatment technologies, such as decentralized desalination and treatment plants that allow wastewater reuse, can help address these challenges.
Decentralized solutions bring water treatment right where it is needed, eliminating costly pipelines to deliver freshwater to the point of use or to remove wastewater. Decentralized treatment offers a cost-effective solution for treating water and wastewater in remote locations and urban areas alike, and can play an important role in improving water security in water-scarce regions.
Contact Fluence to learn more about our decentralized water and wastewater treatment solutions and the benefits they offer to water-stressed regions.