Eight centuries of groundwater supply in Liège: from coal exploitation to cutting-edge hydrogeology in chalk and limestone aquifers

As early as the 13th century, the first drainage galleries were developed in Liège linked to coal mining works. These galleries, called areines in Belgium, had exit points for water flowing out into the Meuse River or the nearest stream in the valley. The water from these gallery networks was directed as drinking water to the public and private fountains of the city. Due to their importance, these areines, called areines franches, were protected by strict laws to avoid potential physical damages or contaminations. In 1697, after merging two drinking water drainage galleries, Jean Roland built a new gallery to collect groundwater emerging from springs at the boundary between the Cretaceous chalk and marls (Smectite de Herve), northwest of Liège. This gallery carried water from the Hesbaye aquifer to the city’s mills and fountains. Five more galleries were built after this first one, and they supplied water collected from the Cretaceous chalk to the city. In the 19th century, the drinking water supply fed by the areines and the Société des Fontaines Roland was insufficient in quantity and quality. In 1855, at the city’s request, Gustave Dumont (André Dumont’s cousin) studied the feasibility of a new network of water supply galleries in the Cretaceous chalk aquifer of the Hesbaye region. His report was published in 1856 and included the first known potentiometric map in the world! Dumont’s report described the best way to increase the city’s drinking water supply and to improve the quality of this water. New galleries were built, and the works were completed by 1869. Since then, the Hesbaye aquifer was a permanent research topic driving the ‘Liege school of Hydrogeology’ at ULiège. These galleries have been extended in several steps, resulting in more than 40 km of catchment galleries in the Hesbaye aquifer, now operated by the Compagnie Intercommunale Liégeoise des Eaux. An overview is also given of the most recent research studies applied to this aquifer in the last 35 years.