Spring waters

Water infiltrates through the Cretaceous limestone upstream and feeds the groundwater table of Haspengouw. All springs are at the level of the water surface. These are formed by the geological formation of the Herve Clay.^[3][4] The flow of the springs was influenced by the following phenomena:

• As the upstream basin developed, the waterproof surfaces were enlarged. During rain, surfaces of materials such as asphalt and concrete and roofs carry rainwater to sewers, rather than seeping into the ground. As a result, aquifer recharge is reduced and urban runoff into the basin increases.^[5]
• This aquifer is a "high groundwater table"^[6] (much higher than the level of the adjacent river, the Meuse); with the development of coal mines, the clay aquiclude was punctured in many places, creating vertical (downward) drainage.^[7] This water was drained lower in the subsurface by galleries and discharged into the Meuse.
• Further northwest, throughout Haspengouw, the waters of this aquifer were intercepted and pumped up.^[8]

All this caused a lowering of the piezometric level and the drying up of the springs of the Rida.^[9]

Recently, a reactivation of springs was observed. A possible cause would be the gradual collapse of the mine galleries, preventing underground drainage and returning the water table to its original level.

The Rida

The main source of the Rida is located in Vottem. This ancient wetland was called li pré Cadjo, and village children bathed there.^[10] Elementary school students came by class to fish for tadpoles.

The current spring is located downstream from a former landfill. However, it produces very clear water, as evidenced by a large deposit of limestone, called cron or cranière in Wallonia. There is also the presence of gours. Such petrifying springs are quite rare north of the Meuse River.

Just downstream, along the Rida, was the farm of Ruwet, still visible on cadastral maps in 1958,^[11] with a pond where the last farmer, Mr. Colson, exploited watercress.^[10] The pond has been filled in but wild watercress still grows, downstream of the spring area.

Between Vottem and Herstal, the course is visible, but channelized; at a place called Au Patar, the Rida briefly assumes its natural morphology.

Main river

The main river begins after the Rida receives the waters of Haren and the Exhaure de Milmort. At this location there are marshy lands on which the only two reed beds in the municipality of Herstal have been developed . There is a remarkable pollard willow with a 3 m circumference, which has not been pruned since at least the year 2000.

Downstream from the little bridge under the Liège-Tongeren railroad line near the Patar farm, there is still a wet meadow, but the water of the Rida is absorbed in a pipe that leads it to the Meuse. Here and there, traces of the Rida's course are still visible in the urban landscape.

The Rida is taken to a place called Bériwa (in Herstal ) (Etymology: "Beau Ruisseau" (in Walloon), according to the 1841 Atlas des Chemins Vicinaux).

Downriver

Downstream of Bériwa, after the Moulin Nozé, the Rida split into two. The main course was diverted through the current location of rue Laixheau and flowed toward Place Licour. During storms, part of the stream ran in its original course, via Rue Faurieux,^[13] where the vault of the passage under an old railroad line is still visible.

Pollution risks

Until the 1970s, there was an open landfill constructed in the valley head of the Rida Valley. This dump was abandoned and reforested, without any specific remediation measures. The Rida River passes under it via a pipe that exits at the foot of the old landfill. In April 2008, Dr. Migeotte, a resident of Vottem, had soil samples analyzed around this landfill at the Malvoz Institute laboratory in Liège. It concluded that the concentrations of cadmium, lead and genuine hydrocarbons posed a risk to human health and the environment.^[16] At the Herstal City Council in October 2008, Mayor Frédéric Daerden was questioned about this by all political groups. Council member Johan Vandepaer (PTB) expressed fears that both the surrounding soil and the waters of the Rida would be contaminated and asked the City Council to analyze samples in the laboratory.^[17] The mayor announced that he had contacted SPAQUE to conduct analyses and verifications at the site, and that he would inform the members of the City Council of the results.

The stream is not included in the DHI Maas surface water mass characterization sheets.^[18]

Upgrading

The 2013 municipal structure plan^[19] aims to upgrade the sections of the Rida that are still open and bring other sections back to the surface when it feasible to do so. However, the municipality is not part of the "Meuse Aval" river contract.^[20]