Understanding low flow genesis in the International Meuse Basin

More frequent and more severe low flow events under a changing climate pose significant challenges to water management and impact various sectors such as agriculture, water supply, navigation, energy and recreation. Low flow events naturally occur as a result of periods of drought. While the generation and propagation of low flows will depend on basin characteristics, these are also influenced by human actions, which can aggravate or attenuate their intensity and duration. Here, we focus on understanding of the genesis and propagation of low flows in the Meuse Basin, a transboundary basin shared by France, Belgium, Luxembourg, Germany, and the Netherlands. Characteristics of the different sub-basins of the Meuse were analysed using an extensive 40-year observed streamflow dataset collated from multiple providers across the basin (e.g., Rijkswaterstaat, SPW, EauFrance, ELWAS-WEB, Vlaanderen Waterinfo, Waterschap Limburg). The collated dataset is used to identify low flow periods by comparing daily streamflow to a 20% non-exceedance seasonally adjusted threshold. The degree of human influence is then determined by contrasting indices such as low flow duration and deficit volume between a benchmark naturalised time series and the human-influenced time series. The storage capacity of sub-basins is analysed through annual and seasonal baseflow volumes as well as sub-basin recession constants. The study revealed that sub-basins like the Rur, Amblève and Chiers are high baseflow contributors, though significant human influences are found. This contrasts with the Upper Meuse, which has a lower human influence, albeit with a limited baseflow contribution. Aggravation of low flows due to human influences can be linked to agricultural land use and water abstractions in the basin as well as reservoirs though these can either aggravate or attenuate low flows, depending on how these are operated. These findings provide important insights into the genesis of low flows and water storage in the Meuse. This understanding lays the foundation for proposing tailored adaptation measures at the sub-basin level depending on its characteristics that have the potential to increase the overall basin storage potential and optimise water management; including through Nature-Based Solutions, improved reservoir operations and other infrastructural interventions.