The Catalan government is considering adopting new exceptional measures to guarantee the quality of water for domestic use in the Barcelona and Girona region in light of the risks derived from the decrease in resources in the Ter reservoirs. The Catalan Water Agency (ACA) is studying emptying the Sau reservoir and transferring its flows to the Susqueda reservoir, also in the Ter, with the aim of increasing the volumes of the latter to have better quality water. The Sau reservoir has such a low level of reserves that it could cause the sludge to emerge and begin to degrade the quality of the water.
The objective of this operation -advanced by the Via lliure program, of RAC1- is to make a more efficient management of the resources that exist in the Ter, in a context in which the water reserves continue to decline; the reservoirs that supply the Barcelona region are at around 27% of their maximum capacity; and if they fall below 25%, it will go from a situation of alert due to drought to a phase of exceptionality, which will entail intensifying municipal restrictions (cleaning streets, gardens...) and domestic (irrigation, swimming pools...) that already have been started.
The operation that the ACA will study this week seeks to preserve at all costs the valuable treasure that is the 28 hm3 that remain in the Sau reservoir. The main purpose pursued by diverting them to Susqueda (both reservoirs are managed jointly) is to enable the water extracted in Susqueda to be captured in the upper part of the water column, thereby achieving a resource of better quality. quality.
"This measure will be maintained as long as the stratification phenomenon does not occur," say ACA sources, since it is about avoiding the mixture of the lower layers of the water sheet with the sludge from the bottom of the reservoir, which can lead to the mobilization of sludge and the reduction of water quality.
It is being studied to increase the current transfer from Sau to Susqueda, and to go from 0.3 cubic hectometres per day to 0.5 hm3, almost double.
Given the low water levels in the Sau reservoir, this measure would entail the need to start an extraction operation for the Sau fish, since the less water there is in Sau, the less dissolved oxygen remains in the reservoir and this can cause mortalities. of fish due to anoxia (lack of oxygen). Preparations were also made in 2008 to undertake this same action. Then, the Sau reservoir was below 13%; the boats were prepared to remove the fish, but the rains in extremis prevented any fish kills.
The fish present mostly in Sau are exotic species (eight of the 9 species are). The idea is to extract the fish and slaughter them (and treat them as waste) and prevent them from dying in the Sau reservoir, since lowering water levels will cause fish kills and a process of decomposition of organic matter, which could also affect the water quality in Sau.
“We estimate that there may be between 20 and 30 tons of exotic fish, and we must manage it well. We must continue to empty the reservoirs to maintain the quality of the water and, in the meantime, collect the fauna that may be there," explained Samuel Reyes, director of the Agència Catalana de l'Aigua.
The extraction of the fish could be done in different ways: with trawlers or manually. "And if we find species that must be protected and saved, we will have to have experts to rescue them and transport them to another place," Reyes clarified.
Meanwhile, the rains of the last days have been scarce and continue without alleviating the drought in the central region of Catalonia. The rainfall has only served to stop the decline in the Ter and Llobregat reserves but not to gain resources. For this reason, the areas in a drought alert situation could go into the exceptional phase.
The director of the Catalan Water Agency, Samuel Reyes, admitted in his interview with RAC1 that the situation is critical. "If it doesn't rain during the spring and fall, we could have user restrictions at the end of the year."
Reyes added that three or four months of uninterrupted rain would be necessary to reverse the drought.
In the event of entering an exceptional phase, the limitations of water in urban uses (gardens or cleaning streets) or domestic uses (irrigation and swimming pools) would be intensified. Reyes rules out having to use boats or trains to have water in the internal basins with fewer resources.
