As water becomes scarce, its quality often deteriorates

Drought and heatwaves result in severe economic losses. To reduce water scarcity, hydrologist Michelle van Vliet argues for a better understanding of the interplay between water use and water quality.

Water scarcity is more than simply a physical lack of water. Water scarcity intensifies due to three main causes: reduced availability of water, increased water use, and deterioration of water quality which makes it unsuitable for certain applications or functions. Droughts and heatwaves are especially critical, because they adversely affect all three of these causes.

Any of the three individual components can contribute to water scarcity, but the interplay of all three together exacerbate it due to important interactions. Reduced water availability during a drought directly increases water scarcity, and on top of that, it has an indirect effect because there is less water available to dilute potential contaminants, which result in deterioration of water quality. For instance, higher salinity levels of water during droughts, can limit its use by farmers for irrigation of crops.

In a previous study in collaboration with an international team of researchers that was published in Nature Reviews Earth & Environment last September, I explained that droughts and heatwaves have a negative impact on water quality in more than two thirds of the case studies analysed. Droughts and heatwaves increase water use by several sectors, such as households and irrigation, which leads directly to increased water scarcity. But it also has indirect effects on water quality. Insight into the complex interaction between water availability, use and quality is therefore essential to find sustainable solutions for water management.

Salt in river water

Each sector is dependent on clean water, whether for irrigation, household use, energy, or industry. Paradoxically, these sectors all contribute to water contamination. Increasing salinity levels, for example, has a negative effect on irrigation water use, but large-scale irrigation contributes to rising sality levels in rivers worldwide.

Sectors are dependent on high-quality water, but they contaminate the water during its use. For example, high concentrations of pharmaceuticals, pathogens and other contaminants limit the (drinking) water available for households, but households are also the most important source of pharmaceutical and pathogen contaminants in waters.

To address these problems, we therefore need to pay more attention to the interaction between the three components: water availability, water use by the various sectors, and water quality. This will help us to make better estimates of water scarcity, particularly under extreme weather events. The good news is that the increased availability of data, computing power and new techniques for intelligent data processing allow us to better study these complex interactions.

Water storage

We will need more than just a better understanding of the causes of water scarcity to find suitable solutions for sustainable water management. However, we will also have to learn thinking in terms of water management scenarios. That is not limited to the traditional approaches to alleviate water scarcity (such as increasing availability by storing more water) or reducing water use by individual sectors, but also improving the quality of the water (for example by reducing the emission of contaminants and expanding wastewater treatment and re-use).

Climate change is one of the biggest challenges confronting humanity in the 21st century. One of the main consequences of global warming is an increase in the intensity and frequency of extreme weather events, such as heatwaves, droughts, and rainstorms. The rise of these events threatens water safety and security in many regions around the world, including the Netherlands, and faces us with difficult challenges. That requires a new way of thinking about water management, driven by improvements in both water quantity and water quality. Only then can we improve water security in a world where extreme weather conditions are becoming more frequent and more intense. The challenges for the new Dutch government, regardless of its composition, is to ensure that the country does not run out of clean water in the future.