Fish in danger after approved emptying of Toules dam
Published: Saturday, Mar 9th 2024, 12:40
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Following the authorized emptying of the dam at Les Toules VS, sediments were deposited along the Dranse d'Entremont river on Wednesday. The extent of the damage to the fish fauna is not yet known, but is likely to be considerable.
The authorized emptying was carried out for safety reasons. It is intended to allow the valve to be used in the event of flooding, as James Derivaz, Director of Dransenergie, explained to the Keystone-SDA news agency.
Dransenergie had been commissioned by the owner of the plant, Forces Motrices du Grand St-Bernard, to empty the plant. Derivaz thus confirmed a report in the Valais daily newspaper "Le Nouvelliste" on Saturday.
Emptying began on Monday. However, shortly before 12.00 noon, the last liters drained contained more sediment than expected, the director explained further.
However, federal legislation stipulates maximum concentrations of sand in water when it is discharged into a watercourse. If the concentration is too high, it can lead to a lack of oxygen and endanger the aquatic fauna. On Wednesday morning, "the values were exceeded and the loss of fish will probably be high", the director admitted. The last time the Toules dam was emptied was 14 years ago.
Turbine at a standstill
Derivaz went on to explain that the entire length of the Dranse from the Toules dam to Martigny VS would be flushed in around two months' time if there was enough water in the dam. In addition, a meeting with the president of the fishermen of Entremont VS is planned for next week to discuss and analyze the situation.
The turbining of the plants in the Dranses production cascade is currently at a standstill. "The various operators can collect the water to turbinate it as soon as it is clean. But it is difficult to give a date at the moment. The financial losses due to this cessation of energy production will have to be assessed," Derivaz continued.
©Keystone/SDA
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