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Michelle van Vliet, Professor of Water Quality and Sustainable Water System, will give her inaugural lecture titled ‘Tomorrow’s water security: Sufficient Clean Water for All’ on September 4th 2025. In the era of climate change and a growing global population, there is a frequently neglected challenge: the worsening state of our water quality. To learn more about this, we interviewed Van Vliet on why water quality is so often neglected, how climate extremes exacerbate this problem, and why integrated solutions are needed.

Water quality as the ‘invisible part of the water issue’. Why is it often overlooked?

“Highly visible water-related challenges such as floods and droughts quickly capture public attention due to their immediate impacts. In contrast, water quality issues often remain overlooked, making them easier to ignore. While we may spot visible signs like algae blooms during hot, dry spells or witness fish die-offs caused by low oxygen levels or pollution, the more gradual deterioration of water quality in rivers, lakes, and groundwater often escapes our notice, at least to the naked eye. As water quality issues often lack visible warning signs, the risks they pose to human health and ecosystems tend to be underestimated.”

Climate extremes are no longer future scenarios, instead, they are present-day realities. How are events like droughts or heatwaves changing the way we need to think about clean water?

“Climate extremes pose several challenges to our clean water supply. Droughts and heatwaves, for example, reduce water availability while increasing demand, especially for irrigation and domestic use. At the same time, water quality shows a general deterioration during these extremes, and this can constrain water use for certain purposes, such as cooling of powerplants due to high water temperatures or irrigation of crops due to high salinity levels. That’s why it’s so important to better understand how these changes in water availability, quality and sectoral use all interact.

We need solutions to improve both water availability and water quality, especially as heatwaves and droughts become more common. At the same time, heavy rainstorms are also on the rise, which can for instance lead to sewer overflows and can also severely affect surface water quality. During dry spells, manure, fertilizer or pesticides accumulate on agricultural land. When intense rainfall follows, these substances can washed into, rivers, lakes and groundwaters, causing sudden increases in pollution levels.”

Due to their invisible character, water quality-related risks for human and nature are strongly underestimated.

Despite its reputation as a global leader in water management, the Netherlands faces persistent challenges in achieving clean water. Why is the Netherlands still falling short?

“Part of the answer is that the Netherlands is a highly densely populated region, with intensive agriculture, industries, urban areas, and traffic, which all contribute to high emissions of pollutants. A large part of these pollutants eventually enter our surface and groundwater systems. Another part is the limited sense of urgency, accountability, and direction from the government, as well as inadequate policy development and implementation over the last years.”

Many current efforts rely on hard infrastructure to improve water quality. But there’s growing recognition of the value of nature-based approaches. What is your view on this?

“Nature-based solutions offer promising strategies to increase the availability and quality of water. For instance buffer zones which act as natural filters, and vegetated areas along rivers providing shade, which helps to regulate the water temperature during heatwaves, reducing water quality deterioration (e.g. due to algae blooms).

It’s also essential to shift our focus towards emission control to reduce pollution at the water source, rather than relying so heavily on hard, technological ‘end-of-pipe’ solutions to treat water afterwards.”

Rather than continually trying to reshape water systems to fit land use or human needs, we should aim to work in harmony with the natural boundaries.

Looking ahead, what kind of water system do you believe we need for the future?

“We really need a shift toward a more climate-resilient water system. That means making sure there’s sufficient surface water and groundwater of suitable quality for human use and nature, and treating it as a common good. Everyone has a responsibility here: government, citizens, drinking water companies, farmers, industry, and nature organisations. Such a water transition is required for a sustainable management of our water resources also during climate extremes like droughts, heatwaves, and heavy rainfall which will become more common. That means improving both water availability, for example by increasing storage, and water quality, by reducing pollution at the source. We also need to cut down on water use across all sectors by water saving measures and improve water use efficiency (e.g. switching to drip irrigation).

What’s important is that we stop trying to bend land and water systems to fit our preferred uses. Instead, we should align land use more with the natural characteristics of the landscape. That includes respecting the natural boundaries of our water systems. Working with those natural boundaries rather than constantly trying to reshape them will help to build a water system that’s much more resilient to extremes in both its quantity and quality.”