Verzasca Lake emptied

VOGORNO

The project is necessary to ensure the safety of the 56-year-old hydroelectric plant - A construction programme has been drawn up that includes monitoring and other measures to minimise the impact on the environment.

Verzasca Lake emptied
The level reached in 1996: from December, for the first time in its history, the lake will be completely emptied. ©CdT/Archive

Verzasca Lake emptied

The level reached in 1996: from December, for the first time in its history, the lake will be completely emptied. ©CdT/Archive

Anyone older than 35 may remember it It was 1996 and quite a sensation to see the level of Lake Verzasca gradually lowering until the traces of the farmhouses and other buildings submerged since 1965, when the hydroelectric plant was put into operation, appeared. As evidence of those days there are various films of the time on the net. It was a partial purging (the third since the start of the activity), but in the valley (and not only) it was lived as a real event. The huge operation that will start in December and will lead, in two months’ time, to a complete draining of the lake from the dam, will therefore be of historical importance. To give you an idea, approximately 85.5 million cubic meters of water will be removed. The project will be carried out in order to allow Verzasca SA to carry out control and revision work so that the dam’s safety can be guaranteed in the future. Considering the scope of the intervention, the impact on the territory will be inevitable. However, the nature of the basin and the measures planned should make it easy to minimize these effects.

The request two years ago

«To comprehend the reasons behind the emptying,« Andrea Papina, director of Verzasca SA, commented to CdT, «one can compare the management of a dam to that of a house. Maintaining it in good condition involves planning a whole series of interventions. We are doing the same thing, and the draining that will take place in the coming months has been planned for a long time. So much so that - as we can see from the notice, just released, with which the State Council authorizes the operation - the relative request was forwarded two years ago (as required by the directives on the subject). «And the canton - Giovanni Bernasconi adds, chief of the Section for the protection of air, water and soil of the Department of Territory - has approved the operation, considering that it is necessary especially for safety reasons. It is in fact impossible to overhaul and clean the bottom outlet of the reservoir - which obviously must always be in perfect working order - without removing the water from it». It is also inconceivable to postpone the emptying of the basin any longer, since - as the government points out - the technical life span of the parts that will be checked and possibly restored (set at between 20 and 40 years) « is by now largely exceeded», something that could have negative consequences on the safety of the plant.

Beyond the technical aspects (the program envisages a first phase of emptying up to an altitude of 310 meters above sea level - the same reached in 1996 - and then, in a second phase, the complete emptying), the planning has taken into account all possible environmental consequences. And this also through the consultation of the Working Group on the drainage of hydroelectric basins, in which representatives of the various cantonal offices as well as those of organizations such as the Ticino Federation of Aquaculture and Fisheries, the association of professional fishermen or the WWF sit.

The question of sediments

The State Council underlines that with the emptying, «up to a maximum of 17 thousand cubic meters of mainly silty sediments, which have deposited over the years near the dam, could be moved». A high quantity? No, in the opinion of the experts, especially after 56 years of continuous activity. «In some ways - clarifies Bernasconi - we are lucky, because the shape of the valley and its catchment basin greatly limit the movement of material. For example, consider that other Ticino hydroelectric plants, even smaller than the Verzasca, accumulate hundreds of thousands of cubic meters of material in a considerably shorter time. From this comes optimism about the possible «side effects» of the emptying. «These - adds the cantonal official - should be limited - and not too important - to the stretch of river between the dam and the lake, while Verbano will likely emerge without major consequences». Also because, Papina concludes, «there will be constant monitoring during the entire intervention and we will always be able to adjust the measures to prevent pollution». The information campaign will now begin, involving the Town Halls of all the municipalities concerned.

©CdT.ch - Riproduzione riservata

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