Following the floods in July, the City of Yverdon-les-Bains' Energy Department, which is responsible for water distribution, has been working hard to ensure that the people of Yverdon receive quality water, even though the natural elements that have been unleashed in recent weeks (record rainfall, record floods) have caused the region's professionals to spend several sleepless nights.
A short reminder about the water supply in the Region and the City:
The Nord-Vaudois region, especially the town of Yverdon-les-Bains, is supplied with water by several resources. The two most important are the wells of Onnens, and the Cossaux spring located at the foot of the Chamblon mountain. During normal rainfall periods, the Cossaux spring covers a third of our consumption, the rest is provided by the Onnens wells. These wells are owned and managed by the multi-purpose association of the Communes of the Grandson Region (ACRG). During periods of heavy rainfall, the Cossaux spring may no longer be usable, as the water from the Jura massif (porous limestone) contains too many impurities (mineral and vegetable).
The heavy rainfall in July and the flooding of Lake Neuchâtel disrupted the water supply in the region:
Last July, rising water levels in the lake caused changes in the flow of water underground:
- The Cossaux spring was suspended for 6 days in early August.
- In the wells of Onnens, we noted an increase in the concentration of organic matter (microscopic remains of plant matter)
As part of our monitoring of the quality of the water supplied, we measure the concentration of organic matter continuously by photometry. As soon as the concentration exceeds certain standards, to avoid bacterial growth, the department increases the chlorination of the water. This work is carried out by all the fountain workers responsible for drinking water, and for Yverdon it is carried out at two locations in Bellerive (under the Château de Grandson) and also by the professionals of the ACRG at the outlet of the water from the wells in Onnens. These precautionary measures are taken to avoid a proliferation of bacteria that love organic matter, their favourite nutrient. To guarantee the quality of the drinking water during the flooding period, we have increased the number and frequency of bacteriological analyses of the water, with daily samples taken in all the districts of the town. The water is also tasted so that the olfactory criteria are also respected. The result? After 3 weeks of the lake's receding, we are relieved and satisfied to see that the quality correction measures have been successful.
No bacteriological pollution of the water in Yverdon-les-Bains was recorded.
What does water taste like now?
Chlorine, when reacting with a variety of organic compounds, produces very odorous molecules. This is why you may have noticed a taste or smell that can be described as "earthy" or "vegetal". This is not the smell of "chlorine", but of the results of the reaction of chlorine with these remnants of plant matter.
How can you avoid this 'earthy' taste?
Aerating the water by letting it sit in a carafe for 20-30 minutes before drinking will reduce the unappetizing smell
Is it safe to drink city water?
Yes, without any problem, from a bacteriological and chemical point of view, the continuous monitoring of the quality of Yverrdon-les-Bains water ensures that the water distributed does not represent any health risk. The level of free chlorine in the network is kept below the legal limits (max 0.1 mg/l). The concentration of organic matter in the water is also below the legal limits.
When will the water taste normal again?
The problem will be resolved in the next few weeks, and the target of early September would be realistic, but it is difficult to predict the exact date when the taste and smell will return to normal.
The lake level set a record in July 2021. We have never experienced a similar period in the memory of professionals in charge of water (30 years). The natural rebalancing of our network's supplies will take place over a period of 3 to 4 weeks, encouraging us to be patient and humble in the face of natural phenomena.
For further information, please contact
Mr Benoist Guillard, Municipal Energy Officer, 024 423 65 70
Mr. Enrico Riboni, Head of the Water Section on 024 423 65 40