2020

A Journey Through the Meuse River Basin:

Deltares: Toward an International Water Balance for the Meuse

Bernard Becker of Deltares is the project manager for RIBASIM, which is developing an international water balance for the Meuse basin under commission from RIWA-Maas. He knows the river basin like the back of his hand: he studied civil engineering in Aachen and was a visiting researcher at the University of Liège. Every year, along with colleagues from across the basin, he organizes a scientific international symposium on the Meuse.

When asked what stands out to him about the 1972 article, Becker notes: "Fifty years ago, describing the Meuse basin was almost entirely focused on high-water peaks. What is new today is that hydrologists investigate drought right alongside high water."

Changes in the Region

To achieve this, insight is required into both water supply and water consumption. "It is the first time we are creating a water balance for the Meuse that looks at the entire river basin."

The computer model Riverbasin Simulation model (RIBASIM) is being used for this research. According to Becker, this software is frequently deployed internationally, for instance, to address severe water scarcity issues in countries like Morocco, Egypt, and Indonesia.

In addition to providing the software, Deltares brings expertise in the hydrology and hydraulics of the river system and its underlying processes: precipitation, water runoff, and groundwater flow.

Becker explains: "The hydraulics for the model are not complicated. Connecting water demand and water supply, however, is. To gain insight into this, we started by holding discussions with scientists across the river basin." Thanks to this inventory, Becker now has a general overview of the major changes in the Meuse basin compared to 1972. He highlights four of them.

The Influence of Reservoirs on the Discharge of the Meuse

"In Belgium, the 'les Lacs de l'Eau d'Heure' reservoir complex was built, consisting of two larger reservoirs and three small ones," says Becker. "This reservoir complex is one of the largest in the Meuse basin. These reservoirs were not mentioned at all in the 1972 article because they were still under construction at the time. Yet, during low water levels, reservoirs are precisely what contribute to the volume of water. They were built to supply the canals with water, which directly impacts the discharge of the Meuse.

By comparison, we know quite a lot about the three large reservoirs in the Rur, including how they are managed. Thanks to these reservoirs, the discharge of the Rur almost never drops below 10 cubic meters per second. During low water periods, the Rur makes a massive contribution to the discharge of the Meuse, which can amount to nearly 50 percent.

A next step in the water balance would be to incorporate insights into the management patterns of the Rur reservoirs into operational decisions for high water. Furthermore, it would be valuable to discuss the volumes of water released from the reservoirs into the Meuse during low water. No international agreements exist regarding this; the three reservoirs in the Rur are entirely owned by the federal state of North Rhine-Westphalia (NRW), making it a domestic matter. For the international Meuse water balance, it is vital to know how the water in these reservoirs is utilized. Up until now, that insight has been largely lacking, which presents clear opportunities for cooperation."

Lignite Mining in Germany

As a second major change, Becker points to the shifting impact of lignite (brown coal) mining. "In the massive 'Inden' lignite mine, the groundwater table is artificially lowered by as much as 300 meters. This affects the Meuse. As a result of drainage from mining activities, water flows away from the Meuse. This was very different 50 years ago. The historical article from 1972 states that the inflow of groundwater was highly relevant in that specific area. That is no longer the case today, as the groundwater is being drawn away by mining operations.

Admittedly, this does not involve massive volumes of water, and furthermore, the extracted groundwater eventually finds its way back into the Meuse via the Rur. Net-wise, the groundwater extraction and the groundwater discharge roughly cancel each other out. However, in terms of hydrography, it is certainly a major shift compared to the past.

Moreover, lignite mining will phase out by 2030, at which point the situation will change once again. Groundwater will then start flowing back toward the Meuse. It will be fascinating to see how this plays out, as the dilution effect of the mining drainage in the Rur will disappear. After 2030, the quality, temperature, and discharge of the Rur water may consequently change. What the exact impact on the Meuse will be is something we have not yet investigated in detail."

Effect of the Meuse Discharge Treaty

A third profound change compared to 50 years ago is the Meuse Discharge Treaty.

"The Meuse Discharge Treaty came into effect in 1995. The 1972 article states that the water discharge at Borgharen during low-water periods was negligible at the time because the Meuse water was being used entirely to feed the Belgian canals."

"That is no longer the case today. When discharges drop below 130 cubic meters per second, the Meuse Discharge Treaty regulates how much water is diverted to the Albert Canal, ensuring that a portion of Meuse water always remains for the Border Meuse (Grensmaas) and the Juliana Canal. In other words, we now consider the discharge at Borgharen to be anything but negligible. During low water, we see that tributaries in Belgium and France supply a large share of the Meuse discharge in the Netherlands."

Effluent from WWTPs in the Downstream Meuse Reach

Finally, Becker notes the growing significance of effluent from wastewater treatment plants (WWTPs) on the water supply of the Meuse. "During low water levels, WWTP effluent flowing into the Meuse via its tributaries becomes relatively more important. I imagine this is also a major difference compared to 1972.

For the water balance, the question then arises as to where the drinking water—which is discharged into the Meuse or a tributary via the WWTP—originates from:

• If the drinking water is extracted from the Meuse, its tributaries, or from reservoirs, then the drinking water extraction and the WWTP discharge roughly balance each other out.

• If the drinking water originates from groundwater, then the WWTP effluent essentially forms an extra source of water in the water balance.

This makes a distinct difference for the water balance of the river system."

Methodological Alignment

The work of the RIBASIM project group, in which Becker and Jaskula participate, aligns closely with the work of KU Leuven, where a water balance for Flanders has been developed. The baseline assumptions for these models have been carefully synchronized.