By Amir Dakkak
"Water scarcity affects one in three people on every continent of the globe."-World Health Organization
What exactly does that mean? What is meant by "Water Scarcity"? How is it measured? There are many different definitions of water scarcity; the simplest one being: the unavailability of adequate amounts of water for human and environmental use. This can be measured using different methods.
The first and most commonly used method of measuring water scarcity is by using the "water stress index". This is the simplest of all the other methods. The water stress index defines water scarcity in terms of the water available for a population in a certain region; measuring scarcity as the amount of renewable freshwater that is available per person per year. This method is easy and simple to use, but its simplicity causes some faults. The water stress index does not account for:
The second method of measuring water scarcity is by using the "criticality ratio". This method accounts for the fact that different countries use different amounts of water and instead defines water scarcity by comparing the country's water demand to the amount of water available; measuring scarcity as the proportion of total annual water withdrawals relative to total available water resources. Although this method avoids the simplistic assumption that all countries have the same demand for water, it still does not account for:
The third method, which was developed by the International Water Management Institute (IWMI), attempts to adress the problems listed above. It includes each country's technological ability and water infrastructure into a country's water sources, recycled water by limiting water use to consumptive purposes rather than total withdrawal, and measures a country's adaptive capacity by assessing its potential for infrastructure development and efficiency improvements.
Although this method accounts for all the faults that were previously mentioned, it fails to account for the ability of people within the country to adapt to low water resources by importing food from other countries or by using water saving techniques and devices. Also, its complexity means that it requires large amounts of time, resources, and data to estimate.
The fourth method is called the "water poverty index". This method attempts to take into account economic resources, such as income and wealth, by measuring:
It's complexity however, makes it more suited for water scarcity analysis at a local scale rather than a national one.
It's very difficult to say one method is better than the other. However, the use of the "criticality ratio" seems to be the most effective method, for it compares the demand for water with its natural availability. It allows policy makers to initiate programs (e.g. desalination) to relieve some of the projected demand for water, and motivates them to lower their demand and consumption of water.
There isn't one definition for water scarcity, and different measurement techniques capture different aspects of the pressures of water scarcity. But all measurement techniques lead to one conclusion: current water levels cannot sustain the continuous increase in water demand unless something changes, now.
References: Global Water Forum: Understanding Water Scarcity, FAO Water: Water Scarcity.
"Water scarcity affects one in three people on every continent of the globe."-World Health Organization
What exactly does that mean? What is meant by "Water Scarcity"? How is it measured? There are many different definitions of water scarcity; the simplest one being: the unavailability of adequate amounts of water for human and environmental use. This can be measured using different methods.
The first and most commonly used method of measuring water scarcity is by using the "water stress index". This is the simplest of all the other methods. The water stress index defines water scarcity in terms of the water available for a population in a certain region; measuring scarcity as the amount of renewable freshwater that is available per person per year. This method is easy and simple to use, but its simplicity causes some faults. The water stress index does not account for:
- The regional differences in water availability.
- Wether the water sources are accessible to humans. For example, the freshwater that is said to be available might be heavily contaminated, therefore unusable.
- Man made water sources such as desalination.
- The different amounts of water used depending on the different countries or regions.
The second method of measuring water scarcity is by using the "criticality ratio". This method accounts for the fact that different countries use different amounts of water and instead defines water scarcity by comparing the country's water demand to the amount of water available; measuring scarcity as the proportion of total annual water withdrawals relative to total available water resources. Although this method avoids the simplistic assumption that all countries have the same demand for water, it still does not account for:
- Man made water sources.
- It ignores water reuse and recycle.
- It doesn’t consider a country's capacity to adapt to lower water availability through changing behaviour or new technology.
The third method, which was developed by the International Water Management Institute (IWMI), attempts to adress the problems listed above. It includes each country's technological ability and water infrastructure into a country's water sources, recycled water by limiting water use to consumptive purposes rather than total withdrawal, and measures a country's adaptive capacity by assessing its potential for infrastructure development and efficiency improvements.
Although this method accounts for all the faults that were previously mentioned, it fails to account for the ability of people within the country to adapt to low water resources by importing food from other countries or by using water saving techniques and devices. Also, its complexity means that it requires large amounts of time, resources, and data to estimate.
The fourth method is called the "water poverty index". This method attempts to take into account economic resources, such as income and wealth, by measuring:
- The level of access to water
- Water quality, quantity, and variability
- Water used for food, domestic, and productive processes
- Capacity for water management
- Environmental aspects
It's complexity however, makes it more suited for water scarcity analysis at a local scale rather than a national one.
It's very difficult to say one method is better than the other. However, the use of the "criticality ratio" seems to be the most effective method, for it compares the demand for water with its natural availability. It allows policy makers to initiate programs (e.g. desalination) to relieve some of the projected demand for water, and motivates them to lower their demand and consumption of water.
There isn't one definition for water scarcity, and different measurement techniques capture different aspects of the pressures of water scarcity. But all measurement techniques lead to one conclusion: current water levels cannot sustain the continuous increase in water demand unless something changes, now.
References: Global Water Forum: Understanding Water Scarcity, FAO Water: Water Scarcity.
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