In the situation of extreme drought, with no forecast of abundant rains in the short term and low water reserves, the Department of Climate Action and the Catalan Water Agency (ACA) have launched a plan to save the little water that remains in the Sau reservoir, which is currently at 10% of its capacity, the lowest figure in recent decades. A plan that, aside from diverting volume from Sau to Susqueda, plans to remove as many fish as possible from the dam to prevent their death due to lack of oxygen from contaminating the water and making it unusable for mouth use. In the current situation, every drop counts.
The precious liquid that the dam still stores would supply a million inhabitants for three months. "The objective is to maintain the quality of the water to make the most of it," explained yesterday the director of the Àrea d'Execució d'Actuacions of the Agència Catalana de l'Aigua (ACA), Elisabet Mas. In order to preserve its quality and guarantee the domestic demands of the Barcelona area and the Girona region for as long as possible, water has already been diverted from the Sau reservoir to the Susqueda reservoir for days. Both belong to the same basin, that of Ter-Llobregat, which supplies drinking water to more than five million people.
Currently, 0.5 cubic hectometres are released per day, a transfer that would stop if a significant deterioration in water quality was detected or oxygen in the lower layers of the reservoir was reduced. That situation could be accelerated by the current high temperatures coupled with the unusually low volume of water in the swamp. They are only twenty meters deep. Experts point out that the reduction in the volume of water in Sau can lead to a decrease in oxygen in the water, a fact that could cause fish mortality if they are kept at high densities.
To reduce the fish density of the reservoir and avoid worsening the quality of the water resource, about two tons of fish per day will be removed, which will be slaughtered. The head of exotic spices and conservation of the Climate Action Department, Jordi Ruiz, indicated yesterday that there are no protected species or threatened habitats in this area. A study establishes ten species of fish present in the Sau reservoir and that 90% of them are exotic. In this group would be the catfish, carpín, carp, sandra, bleak or sunfish, among others. Only one of the species that inhabits the swamp is not exotic, but it is not typical of the Ter river basin either. It is the Ebro barbel.
Ruiz explains that the legislation requires the sacrifice of exotic species and that the same will be done with the few Ebro catfish that are expected to be found. “It is a matter of scientific coherence, moving fish from their habitats in which there has been a great mortality, can cause health problems and affect other native fauna,” says Ruiz. If any native species is found, it would be moved to the corresponding section of the river.
Those who will be in charge of fishing will be two boats from the Blanes brotherhood that will use a traditional system consisting of submerging the net to a certain depth, preventing it from destroying the bottom. Two other pelican-type boats will be used to collect species on the surface in the event of mortality in the reservoir. A fifth electric fishing boat, which yesterday carried out a survey to quantify the fish that the swamp can harbor, will be used only in corners and very small spaces or as a support for the fishing boats, and in some cases it could even be opted for hand fishing. The extracted specimens will be treated by a company specialized in the treatment of biomass.
Yesterday, a crane lowered three of the boats that will start working tomorrow onto the sheet of water. It is estimated that the operation could last a month and a half.
