Located in the commune of Ayent at the bottom of the Lienne valley and at the foot of the Rawyl pass, the Tseuzier (or Rawyl) dam is 156 metres high and 256 metres long. Its reservoir has a volume capacity of 50 million m3 and covers an area of 85 ha and is 1.3 km long. Electricity is produced by three power stations: the Samarin power station, which has a capacity of 0.9 MW, the Croix power station, which has a capacity of 66 MV, and the Saint-Léonard power station, which can produce up to 17 MV (source: https://fr.wikipedia.org/wiki/Barrage_de_Tseuzier).

In addition to its hydraulic use, the water from the Tseuzier dam is used to supply drinking water to the communes of Ayent, Icogne and Lens; it is also used to irrigate crops via the Grand bisse d’Ayent. In addition, the water from the dam is used to produce artificial snow to cover the slopes of the Anzère ski area. On average, 480,000 m3 of water from the dam are filtered for the drinking water needs of the Ayent municipality and 140,000 m3 are dedicated to mechanical snowmaking. Comparable volumes are used by the commune of Icogne. Like many other municipalities that own the right to use water, the municipality of Ayent – together with the other concession-granting municipalities – will have to negotiate the return of the concession for the operation of this facility by 2037. This process is generally long and tedious (it takes an average of 15 years!) in addition to being very complex.

To best negotiate the value of new concessions, many parameters need to be taken into account, such as the condition of the hydropower plant and the value of the dry part. These points must be studied and characterised while taking into account the financial risks and the search for potential partners.

In the context of climate change and water scarcity, it is now necessary to re-evaluate the priority sectors benefiting from water use rights, while taking into account economic, societal and environmental interests. These points add additional parameters to the equation and make modelling even more complex. How then to put a fair value on water according to its different uses.

Moreover, municipalities often do not have the necessary skills to carry out these studies (source: https://www.lenouvelliste.ch/valais/retour-des-concessions-un-document-permet-aux-communes-valaisannes-de-sy-retrouver-1067882).

In order to prioritise the different uses and to value each litre of available water at the right level, we would like to have a tool that allows us to assign a value to water, according to the different uses that can be made and the needs of the population. This tool could be used as a guide or decision aid for municipalities, in particular to support them in planning long-term investments in the water network or in pricing water according to use.