“It is possible: a healthy groundwater system as water buffer and water source”

On 14 February 2025, special professor Ruud Bartholomeus delivered his inaugural lecture. Since 1 July 2024 he has held the Plant Water Stress and Regional Water Management chair at Wageningen University & Research (WUR). This is not unfamiliar territory for him, because Bartholomeus had already been working one day a week at Wageningen’s Soil Physics and Land Management Group as a visiting researcher since 2017. The rest of the week he is and will remain KWR’s Chief Science Officer (a function he shares with Milou Dingemans) and Principal Scientist in KWR’s Ecohydrology team.

Becoming a professor has never been his ambition, but he says that the role offers him even greater opportunities to do what he has already been doing for years: ‘I thoroughly enjoy connecting fundamental and applied science and scientists with each other. My work at KWR revolves around applied research and policy in practice; as a professor, I wear a scientific hat as well, and I work on the solid knowledge base which is so important for KWR and water practice. This allows me to connect my KWR work and colleagues with scientific developments and valuable academic networks. At the same time, I bring the valuable perspective of water practice to the university, along with pertinent questions arising in water practice that call for further fundamental research.’ Bartholomeus extends this connecting role to many of his other activities; he is for instance chair of the Netherlands Hydrological Society, member of the Expert Network on Freshwater and Drought, and member of the Blue Route core team within the Dutch National Research Agenda.

Link between academia and water practice

Bartholomeus himself learned a great deal during his doctoral research at VU Amsterdam by dividing his time between the academic environment and KWR. ‘I offer that valuable experience to other doctoral students as well. As visiting researcher, I already supervise several PhD students, such as my KWR colleague Janine de Wit and Mark van den Brink. Mark works in the NWO WaterScape programme on climate-robust and -adaptive water systems at landscape scale, which sustainably provide sufficient freshwater. This calls furthermore for a transformation of water and management systems, and links the academic world with the practical application of scientific research – a truly valuable programme.”

“As a professor, I will contribute more to the teaching at WUR, for example, by introducing the perspective of water practice into the course material, but most of all by continuing to supervise doctoral students and interns and, via KWR, offering them a complementary link to water practice. In addition, the chair opens even more opportunities to draw attention to the question of a robust and sustainable freshwater provision, in which the different functions of water are brought into, and remain, in balance – all matters that I am very glad to tackle with water-practice and academic colleagues, and that also applies to this chair. It is for me primarily a means of collaborating even more, while simultaneously giving others room. I love to see people grow, and am for instance very happy with the way in which the voices of young water-sector experts are strengthened through initiatives such as GRROW. For me, collaboration is mostly about offering each other opportunities.”

Using water sustainably

Bartholomeus’s research at KWR and WUR is strongly focused on freshwater availability, now and in the future. Bartholomeus: ‘To use groundwater is to play with a delicate balance. If the groundwater level for example increases or decreases by as little as 20 cm, this can already have a significant impact on functions on the surface. Plants experience water stress when they have too much or too little water in their root zone, and that naturally has implications for agriculture and nature, which is why water management on a regional scale is needed.

Precisely the subject of this chair. There is an enormous amount of water in the Netherlands, but the reality is that we can only sustainably use a small portion of the water available. We have to be continually attentive to the negative impacts on nature or on other stakeholders and water users, like drinking water utilities, industry and agriculture. To sustainably meet our water demand, we need cross-sectoral measures, often at the interface of the ecological water system and of the water cycle, in which water is used by humans. Because, if we do not change things, the anthropogenic water demand will just keep on growing – and that is not tenable.”

Save, reuse and infiltrate water

Where does Bartholomeus see solutions for a robust and sustainable freshwater supply? ‘We have three knobs we can turn when it comes to reducing the impact of humans on the water system,’ begins Bartholomeus. ‘In the first place, we can retain more of the rainwater longer in the subsurface. Second, we can take water-conservation measures to reduce the amount of water we need to abstract. For instance, we can reuse water instead of discharging it. And the third knob concerns the active recharge of groundwater. We know how to do this: we have for example been infiltrating water in the dunes for the production of drinking water for a very long time. Close attention to water quality is crucial in this context of course, as is the balance between excessively dry and excessively wet conditions.”

Longer retention of water in the system rather than its rapid discharge

“But, in any event, a water-rich country like the Netherlands must first of all ensure that the available rainwater is buffered as well as possible in the subsurface – we have to retain more water in the system. This implies creating a higher groundwater level, which has consequences for instance for land-use. This means that not all functions will remain viable, which is something that needs to be carefully considered across society. Where do you retain water, and what use do you make of drier and wetter parts of the water system? You can only make decisions about measures of this kind at the regional scale.”

Technology or nature?

“The solution pathways are therefore really quite clear,’ says Bartholomeus. ‘But there are still different approach options: how much are we going to let technology play a role, or do we actually resort as much as possible to nature-based solutions which make use of the natural system? Combinations of the two are often also possible, if you consider the water cycle and hydrological water system truly as a single system. Can the groundwater that we now use and, following treatment, discharge into surface water, be reused in irrigation, industry or groundwater recharge for example?”

”Such cross-sectoral measures involve numerous aspects. Apart from water quantity, naturally also water quality, but the entire governance as well. How you deal with this is not part of my chair, but the socio-scientific side of the question is naturally a subject about which various colleagues at KWR, and in the water sector more broadly, are accumulating more and more knowledge. Discussions are getting underway and expertise is growing in the areas of stakeholder management and spatial planning processes, which are both key to reaching sustainable solutions. Solid knowledge of transition theory is incredibly important in helping stakeholders and policy-makers to reach well-considered, though sometimes painful choices.”

Hydro-illogical cycle

Nonetheless, according to Bartholomeus, the focus in the Netherlands is excessively directed at flood control, and too little at the organisation of a robust system that can continuously provide us with sustainable water: ‘I see the “hydro-illogical water cycle” in full operation: we get worried whenever dry periods are longer, but as soon as it starts raining again, it’s business as usual, so that the drought problem is not solved.”

”This is a pitfall. The memories of the dry summers of 2018, 2019 and 2020, seem in the meantime to have been superseded by those of the wet summers of 2023 and 2024, so that the focus is again directed more at preventing excessively wet conditions. While the projections indicate that, besides peak downpours, we actually also need to prepare ourselves for lengthy dry summers. It is good that the water utilities, with their ‘Actieprogramma Beschikbaarheid Drinkwaterbronnen’ [Drinking-Water-Source Availability Action Programme], ask that attention now be paid to future water shortages, but the problem is much broader than simply the provision of drinking water. We really need to make this as clear as possible. I will also dedicate myself to this at KWR and via my chair at WUR.”

Active role for scientists

Bartholomeus feels that scientists have particular roles to play. ‘You have to do thorough research, but you also have to actively disseminate the knowledge acquired. In doing so, you always need to be careful that you don’t become some lobby’s pawn. Scientific results are complicated, and the different parties have a tendency to present and interpret information in their own favour; selective shopping and wishful thinking are ubiquitous. As a scientist you have to constantly present the objective evidence base and, at the same time, ensure that the results of your research work are transmitted to the world to be put to use. It is therefore not enough if you simply write an article or a report that ends up in a draw somewhere – this applies to both academics and to researchers at institutes like KWR.”

”’Bridging science to practice’ is happily not only KWR’s motto, but it is actually what we do with our work. Knowledge needs to flow as fluidly as water does. As a scientist, you have to dare to ask that attention be paid to the results of your work, so that they can be of benefit to society – in all of its dimensions. I therefore take every opportunity to make sure that solid knowledge is taken into consideration in the public debate and around decision-making tables. Because something really needs to happen in the area of sustainable freshwater availability.”

Nitrogen problems and postponement

In this regard, Bartholomeus in fact sees some similarities with the current issues concerning nitrogen. Solutions to the nitrogen problems have long been postponed – so that now, apart from the problems for nature, agriculture and residential construction for example are having to deal with big problems and lawsuits. ‘The constant postponement of choices and solutions could end up just as disastrously when it comes to drinking water availability,’ says Bartholomeus. ‘“Gentle healers cause stinking wounds” as the Dutch proverb puts it. We must dare to jointly take decisions now – as I’ve said, the solution pathways are laid out; the details we will fill in together.”

Gentle healers

What happens if the gentle healers get the upper-hand and solutions for freshwater availability are always put off? ‘As a result of a constantly growing demand for water, and increasingly lengthy and frequent drought, really big problems will arise.’ Water will still continue to flow from the taps in the Netherlands, even if probably at lower pressure. But a choice for the provision of drinking water might be made at the expense of water for other users, such as agriculture, and for nature and biodiversity. And the impacts on nature could be irreversible.”

Necessary and painful changes

Bartholomeus considers himself an optimist and is moreover not afraid of a challenge. ‘I am going to do all I can to make sure that the knowledge produced in the academic world and applied research institutes like KWR contributes to carefully considered choices. I think it can be done. I think that we can create an environment in which different water functions can coexist. I expect that these functions will not be as interwoven as they are now, and that we will have made conscious decisions in spatial planning and management – and that unfortunately implies that we will no longer be able to do certain things in certain places.”

”This is what makes change so difficult: necessary and sometimes painful changes cause grief and therefore require time. This is why I am glad that the social sciences are increasingly being deployed in research into the necessary transitions, and that I see how young researchers are breaking through old structures. Today, it often seems that things are moving slowly, but some change is actually already happening.”

Healthy groundwater system as buffer and source

And where can these changes take us? Bartholomeus: ‘If we do it right, in the future we will have a healthy groundwater system that we can use as a water buffer and water source, primarily because we will have adjusted our water- and land-use to that system’s possibilities. Technological solutions will certainly be able to make a contribution, for instance by enabling water reuse or the use of brackish water, but our biggest advance will entail giving water and soil greater priority in our decision-making. First the water, the rest follows later, as I summed it up many years ago at Larenstein.”