Drinking-Water Conservation Symposium: How to get to 100 litres daily for each Dutch person?

Behavioural change, legal measures and application of valuable Flemish lessons

Around 50 drinking water experts from the Netherlands and Flanders attended the drinking-water conservation symposium held at KWR on Tuesday, 7 February. The participants concentrated on the question: How can we move households to save drinking water? Over 20 years’ experience in Flanders has produced good results: the Flemish now consume an average of 89 litres of tap water, 11 litres of rainwater and 2 litres of groundwater per day. The Flemish experience offers important lessons for the approach in the Netherlands, where behavioural change and legal measures are being applied to reduce consumption, which is currently about 130 litres daily per person, to 100 litres daily in 2035.

In response to water scarcity, the Ministry of Infrastructure and Water Management has set an ambitious water-conservation objective: a reduction in the daily consumption of drinking water of the average Dutch person from about 130 litres to 100 litres in 2035. Naturally, industry can also still do much to save drinking water, but since households account for 90% of drinking water consumption, their savings are crucial. This is the reason behind the growing policy interest in drinking water-saving measures, both through adjustments in the behaviour of customers, and the substitution of drinking water by means of rainwater systems or the application of greywater systems.

Flemish approach

Adelheid Vanhille, of the Flanders Environment Agency, kicked off the symposium on 7 February with an overview of the Flemish approach, in which the focus has been placed over the last 20 years on the use of rainwater and household water instead of drinking water for applications that do not require water of potable quality. Examples include water for flushing the toilet, using the washing machine, or watering the plants. Initially, a primary impetus behind this approach was to reduce the impact of flooding caused by heavy precipitation. Every Fleming is obligated to install rainwater storage in new buildings with surfaces of more than 40m2.

Rain- and household water

Besides the increased use of rain- and household water, the Flemish approach also includes awareness campaigns as well as tools to help customers reduce their drinking water consumption. This began with a big campaign launched in 2000. Thanks to a package of measures, about 11 litres of tap water per person, per day has been replaced mainly by rainwater. Although the total water consumption has remained at a relatively constant and low level, the measures have resulted in a significant drop primarily in the consumption of drinking water. Currently, the average Fleming uses 89 litres of tap water, 11 litres of rainwater and 2 litres of groundwater per day. That is a great deal less than the Dutch daily drinking water consumption of 129 litres per person!

Attention to contamination risk

An important point of concern in the Flemish approach is that the use at home of two types of water can lead to problems, particularly the contamination of tap water by rainwater. Mistaken connections by do-it-yourselfers appear to be the main reason in such cases. When a choice is made to diversify the water types, colleagues from the Flemish drinking water utilities therefore recommend that the other water either be kept outside, or (if a choice is made for rainwater systems) that the installation and maintenance for a group of houses be carried out by professionals. A drinking water utility could in such instances perform this professional role.


Apart from rainwater, treated greywater is also an option, for example, for toilet flushing. This treated greywater has the advantage of not being dependent on the weather. Moreover, the use of smart technologies can also provide great added value in this instance.

KWR research

Following the morning programme, Stefanie Salmon and Stef Koop took care of the afternoon session on behalf of KWR. They discussed the effectiveness of different types of conservation measures [behavioural, economic and legal (obligations)], the principles of behavioural change, and opportunities for water savings.

Behavioural change

Besides raising awareness of the problem of water scarcity, it is important to work with the daily, unconscious behaviour when it comes to water use. The results of the Behavioural Influence in Practice pilot project show that helping customers with shower planning for instance produces a temporary water saving. This approach is therefore of interest during summer periods.

Personalised messages more effective

Awareness campaigns or general water conservation tips are indeed effective, as stand-alone measures, in raising the knowledge levels of customers, but they do not lead to demonstrable water conservation. On the other hand, sending consumers personalised messages, in which households are compared to each other, has proven to be a behavioural measure that does result in water conservation.

Smart water meters

Smart water meters are an important tool in increasing the effectiveness of the behavioural measures. Although an efficient operational management can be seen as the main benefit of a smart meter, drinking water savings can represent an interesting side benefit – as long as the water meter is adapted intelligently to the desires, needs and experience of customers. It makes sense to apply a phased introduction of the meters, which allows for experiments to identify the approach that produces most drinking water savings.

Limited effect of economic measures

Economic measures presumably have a limited effect because of the low price of drinking water, and the reduced scope for significant price increases.

Need for legal measures

Legal measures, such as making water-saving equipment obligatory for landlords, or the much-discussed imposition of rainwater storage requirements for new buildings, are very necessary to advance towards the policy objective of a daily consumption of 100 litres of drinking water per person in 2035.

In short, lots of work still needs to be done! The participants were unanimous during the interactive discussion about the shared societal responsibility for drinking water conservation. The drinking water sector can take on a proactive role in the effort, but at the same time it does not face the task alone. A strong focus must be directed at testing which conservation measures are effective in practice, and, for this, collaboration with public authorities, residential builders and technology developers is indispensable. Knowledge, insight into and understanding of the motivations of different types of customers – customer perspectives – are a logical starting point here.

Symposium Drinkwaterbesparing feb 2023

Drinking-Water Conservation Symposium at KWR – February 2023