2020

A Journey Through the Meuse River Basin: University of Leuven on Drought in Flanders

Patrick Willems is a professor of water management at KU Leuven. Specialized in hydrological extremes, he knows a great deal about floods and droughts.

"We build water balance models to simulate the water system. This allows us to calculate the impact of climate scenarios and climate adaptation strategies."

When asked what has changed in the Meuse basin over the last 50 years, Willems notes: "What is new is that we are increasingly dealing with salinization in the Albert Canal as a result of drought. In Flanders, the drought of recent years hit hard." He explains further.

The Importance of the Meuse

Flanders lacks large rivers that supply sufficient freshwater, making water inflow via the Meuse critically important. To supply Flanders with water, seven canals—the Campine canals (Kempische kanalen)—were constructed between 1827 and 1947. Of all the Belgian canals, the Albert Canal is the most vital, linking Liège to Antwerp.

Normally, the average discharge of the Meuse is 250 cubic meters per second. Prolonged drought led to exceptionally low Meuse discharges in 2019. By September 2019, the Meuse discharge at Liège (just upstream from the branch to the Albert Canal) dropped to barely 35 cubic meters per second. The situation was critical, carrying major consequences for the use of the Albert Canal.

The Albert Canal

"The Albert Canal provides 40 percent of the drinking water supply in Flanders," Willems says. "This Flemish drinking water is produced by Water-link. Simultaneously, together with the Port of Antwerp, the Albert Canal serves as the most important shipping and industrial axis, where major (chemical) companies are located. The waterway is managed by De Vlaamse Waterweg (The Flemish Waterway). Furthermore, the Campine canals are crucial for agriculture, the irrigation of nature reserves, and feeding recreational and fishing ponds.

The Albert Canal draws water from the Meuse and runs all the way from Liège into the Port of Antwerp. When the supply from the Albert Canal is low, brackish water from the Scheldt is let into the port docks to maintain their water levels. This creates a fresh-saline mixing zone. If there is insufficient freshwater during dry summers, the salt advances further toward the Albert Canal. During the past two dry summers, the salt even penetrated almost up to the intake point for drinking water. Fifty years ago, salinization did not exist there. That is entirely new."

He continues: "We expect that salinization will become an increasingly severe problem in the future due to climate change. This is a source of great concern in Flanders. Ever since those dry summers, intensive research has been conducted into water availability and how to manage it in the future."

Vision on Drought

To enable the right decisions during periods of low water and water scarcity, the Flemish government commissioned KU Leuven to develop a decision-support toolkit. This resulted in a 'reactive assessment framework' (reactief afwegingskader), which is broadly comparable to the Dutch 'Priority List for Water Allocation' (Verdringingsreeks), though more detailed and flexible.

"A framework like this did not exist in Flanders before; political choices regarding water allocation were often subjective," says Willems. "With this assessment framework, we want to provide decision-makers with objective information. This data also helps substantiate these choices and explain them to the affected users."

To develop a coherent vision on drought, existing calculation models were integrated into a new toolkit: the reactive assessment framework. This makes it possible to visualize exactly where water shortages will occur during periods of scarcity, as well as the effects of potential measures (or combinations thereof). Moreover, the models factor in the costs and benefits of intended measures, alongside ecological aspects.

The Flemish Water Balance

Which existing calculation models are involved? Willems explains: "For instance, our own custom-developed calculation models for the water balance of navigable waterways and unnavigable watercourses; calculation models for rainwater availability, and for the filling levels of storage reservoirs used for drinking water production."

Willems continues: "To draw up a water balance, you need insight into supply and demand. The bulk of the work went into analyzing water use. For this, we had to integrate many different types of data. It was the first time we solved such a puzzle in Flanders. Broadly speaking, we now have a clear picture of water demand (by industry, shipping, agriculture, the drinking water sector, and households) and water supply (surface water, deep and shallow groundwater, reused treated wastewater, and rainwater)."

The question arises: can this information also be used for the Dutch water balance? "Unfortunately, this information on water use is region-specific and therefore only applicable to Flanders. However, in the future, it is logical to create a joint water balance for the entire Meuse river basin. We are glad we can exchange information with RIWA-Maas and Deltares."

From Case Study to Reality

Last year, the Flemish water balance—the 'reactive assessment framework'—was put into practice on the Albert Canal. "In September 2019, the situation became critical. The flow rate of the Meuse at Liège fluctuated between 30 and 40 cubic meters per second. We calculated the effects of various measures. This showed that pumping back lock-loss water at the sluices was the most cost-effective solution. Installing pumps at locks to compensate for lockage losses therefore became the highest priority measure. Many locks were already equipped with these pumps, but where they were still lacking, mobile pumps were deployed."

However, this measure alone proved insufficient to tackle the water shortage. "The second priority measure was 'grouped lockage' (passing multiple ships through at the same time). A new calculation module had been developed for this, which provided insight into ship waiting times in relation to water savings. This second measure was implemented as well, in combination with a suspension of recreational boating."

With these measures, Flanders managed to bring the water scarcity under control. But what if drought and water scarcity become even more extreme due to climate change?

Willems concludes: "Using climate models, we can calculate additional measures. This includes the partial and phased closure of water intakes. These are the locations where water is abstracted from the canals, for example for irrigation, recreational ponds, and fishing ponds. This would start with a 50 percent closure, followed by 80 percent.

If the drought and water scarcity worsen even further, restrictions on water intake for companies come into play. First, companies that consume a lot of water but have a relatively low economic impact. Next, companies that consume less water but carry greater economic weight. As an absolute last resort, intake restrictions for drinking water production would be introduced. In the worst-case scenario, 40 percent of Flemish citizens would no longer get water from their taps."