My problem with water scarcity measurements, especially the Falkenmark Indicator

My problem with water scarcity measurements, especially the Falkenmark Indicator

Water scarcity, what is it? Water scarcity can be broadly understood to mean a lack of access to an adequate quantity of water to fulfil human and environmental uses, or, in very basic terms means demand exceeds supply. There is not one all-encompassing definition for what water scarcity is, as different indicators measure different types of water scarcity.

Water scarcity is caused primarily by two reasons: growing freshwater use, and depletion of usable freshwater resources. Within water scarcity there are 2 types; physical water scarcity and economic water scarcity:

Physical Water Scarcity = When a region or country has inadequate natural water resources available

Economic Water Scarcity = When a region or country has adequate natural water resources available but poor management (usually a lack of investment and infrastructure) restricts access.

Falkenmark Indicator

So how does one go about measuring water scarcity? There are many different measures but one of the most commonly used measures of water scarcity is the ‘Falkenmark Indicator’ or the ‘water stress index’. Developed in 1989 the indicator is based on the estimation that a flow unit of one million cubic metres of water can support 2,000 people in a society with a high level of development. Water availability of a country of <1,700m³/capita/year causes water stress, and water availability of a country of <1,000m³/capita/year causes water scarcity. The key difference between water stress and water scarcity is time, with water stress tending to mean a lack of access to water for a specific period of time whereas water scarcity is the lack of access to water in the long-term because of unsustainable usage. This indicator is popular as a measurement as it’s straightforward, easy to use and the data needed is readily available. However, despite the global acceptance of this indicator there are many shortcomings:

1)    The Falkenmark indicator only measures water scarcity at a country level, and can ignore important regional differences in water availability.

2)    The Falkenmark indicator only considers renewable surface water and groundwater flows within a country. This means man-made-sources of freshwater (e.g. desalination plants) are ignored

3)    It does not account for whether these water sources are accessible e.g. some freshwater resources may be stored deeply underground or heavily polluted

4)    It does not take into account that different countries, and regions within countries, use different amounts of water e.g. in Australia most of the demand for water is focused around the major urban and agricultural centres in the Murray-Darling Basin, with much less used in the sparsely populated centre.

5)    The Falkenmark Indicator does not reflect changes in water use demand due to climates, lifestyles, adaptive capabilities etc. In one country 1,700m³/capita/year may satisfy water demands, but in another will be far too low.

As population growth increases there will be more pressure on water resources, as the amount of groundwater and freshwater will stay relatively constant, so therefore population growth multiplies the water requirements set by Falkenmark. However, this indicator fails to include how technology and people’s adaptive capabilities will change water consumption, as water needs will not stay static, they are dependent on income, lifestyle and attitude.

Criticality Ratio

An alternative way to define water scarcity is by using a criticality ratio. The criticality ratio measures water scarcity by comparing water use to availability ,and disregards the assumption that Falkenmark makes that all countries have the same demand for water. The criticality ratio measures scarcity as the proportion of total annual water withdrawals relative to total available water resources, and a country is said to be water scarce if annual withdrawals are between 20-40% of annual supply, and severely water scarce if annual withdrawals are larger than 40%.

While less simplistic than the Falkenmark Indicator, there are still limitations. Again the ratio does not consider man-made increases in water supply, does not consider water withdrawals that are recycled and reused (e.g. grey water) and does not consider the capacity of countries to adapt to lower water availability through changing behaviour or new technology.

International Water Management Institute Approach – Waterism Model

In the International Water Management Institute (IWMI) assessment ‘A Comprehensive Assessment of Water Management in Agriculture’ they attempt to measure water scarcity and avoid the limitations associated with previous indicators listed above. Their approach measures country’s water infrastructure (such as desalination plants), recycled water (they limit measures of water demand to consumptive use, instead of total withdrawals) and also measure the adaptive capacity of a country by assessing its potential for infrastructure development and efficiency improvements. Using these measurements, the IWMI classifies countries as either physically water scarce or economically water scarce. If a country is economically water scarce they are predicted to be unable to meet their future water demand without investment in water infrastructure and if a country is classified as physically water scarce they are predicted to be unable to meet future water demand even with investment in water infrastructure.

While this approach is undeniably more complicated and yields far superior measurements as to whether a country actually is water scarce, the amount of data, time and resources needed to calculate this measurement are huge, and data such as a country’s water infrastructure may not be readily available. Additionally how does one measure a country’s water infrastructure and measure its efficiency? A major critique of the IWMI approach is that virtual water is not used in the measurement. As previously discussed, countries are able to import food which drastically reduces their water usage, and means that richer countries are able to manage their water scarcity more efficiently and reduce their water usage by importing water-rich crops. Therefore wealthy nations are more able to adapt to reduced water availability than poorer nations, so when comparing country’s water scarcity levels if virtual water is not included results will be positively skewed towards richer nations.

Summary

There is therefore no single definition of what water scarcity is, different measurements yield different results and there isn’t one measure which accurately captures every aspect. In figure 1 I have included the 3 above indicators which all attempt to measure water scarcity, and which are all different. Therefore, we should never rely solely on 1 indicator to measure water scarcity as 1 indicator may not necessarily reflect the true water scarce conditions in a country. Instead when discussing water scarcity using an indicator we should always be aware what aspects of water scarcity are being measured, and recognise that one indicator is not, by itself, enough to reveal the true picture.

Figure 1 – IWMI Waterism Model

Figure 2 – Criticality Ratio

Figure 3 – Fallenmark Indicator