The desalination of seawater and the reuse of treated and regenerated flows are determining factors for the Barcelona region to have so far overcome the specter of domestic restrictions. These resources have prevented this territory from entering an emergency situation due to the current drought. The reclaimed water at the El Prat station has turned out to be a fundamental resource: a constant and reliable flow that allows us to glimpse to what extent the supply can stop depending on the unpredictable rain. This is the dictionary of drought.
Work has begun on the expansion of the Besòs groundwater treatment plant (Vallbona, Barcelona), which will make it possible to multiply water production by four in less than a year, thanks to modern ultrafiltration techniques and reverse osmosis. It is also planned for the first time in history to capture water directly from the Besòs river to make it drinkable.
It is now 105 liters per inhabitant per day in the 23 metropolitan municipalities served by Aigües de Barcelona, very close to the minimum of 100 liters per person per day recommended by the WHO.
Desalination is already the main source of supply in the 23 municipalities served by Agües de Barcelona, where it covers 33% of the demand. The Blanes and El Prat desalination plants are operating at full capacity.
The level of the Ter and Llobregat reservoirs (Sau, Susqueda, La Baells...) are at 26% of their maximum capacity. The rains of the last few weeks have served to stabilize the reserves, but they have been weak or moderate, with very localized storms. Therefore, reserves have barely improved. For the reservoirs to recover a desirable level, a rainy episode of several days is needed, with abundant, continuous and persistent rains.
It would be declared if the reservoirs are below 16% of their capacity and would entail a new twist to the restrictions (including in this case the application of measures that would limit the use of water in basic services).
Sending regenerated flows (from this station) upstream of the Llobregat to be reused is the great action in this drought. The resources are pumped to Molins de Rei to be discharged and diluted in the river, to be a water treatment plant for Sant Joan Despí, where they are captured, filtered and distributed. Pumping started with 200 liters per second; now it is 1,500 litres/second and it is hoped that it can be increased to 1,800 litres/second. Reclaimed water is the second largest source of supply in the immediate Barcelona environment (accounting for 25%) and arouses great development expectations.
The exceptional situation affects 495 municipalities (almost 6 million inhabitants) in the basins of Catalonia. The limitations on the use of water are concentrated in the agricultural, livestock and industrial sectors (with cuts of 40%, 30% and 15% respectively); and, in addition, the use of drinking water for irrigation of parks and public and private green areas has been prohibited, to avoid domestic restrictions.
The supply in the Barcelona region is fed by the Abrera and Sant Joan Despí water treatment plants (which treat water from the Llobregat), the Cardedeu water treatment plant (Ter), the Besòs wells (Vallbona in Barcelona) and the Llobregat (Cornella and Sant Feliu), the desalination plant of El Prat and the regenerating plant of the latter municipality (which cleans the treated sewage before being reused). The water treatment plant of La Llagosta, which was not able to start in the previous drought (2008), has also come into operation.
If the emergency phase were to be reached (with reservoirs at 16%), the current daily municipal water supplies for all uses (230 liters per person per day) would undergo successive twists until leaving them at 180 liters (with reservoirs at 10%). and 160 liters (reservoirs at 5%). In this situation, local administrations should reduce the pressure or introduce hourly cuts in the supply. In any case, the sensitive services or customers identified by the municipalities will have guaranteed supply in all cases.
The Barcelona region has circumvented domestic restrictions thanks to desalinated and reused water. Between 2022 and 2023, desalination and wastewater regeneration as well as water from drying wells have contributed more than 241 hm3 of water (92 hm3 from desalination, 93.3 hm3 from regeneration and 56 hm3), This amount of water is more than what fits in the Susqueda reservoir (which, when full, has the capacity to hold 233 hm3). Without this contribution, today we would already be in the emergency phase, according to the Agència Catalana de l'Aigua.
"If we hadn't had alternative sources, that is, if we hadn't had desalination plants and reuse, at this time we would be talking about restrictions in the metropolitan area," say the technicians from Aigües de Barcelona. For this reason, they ask that after the drought the reused water continue to be used as a structural element for the supply
It is being a primary resource. This is a constant and reliable source of water that can be used without relying so heavily on rainfall, thus allowing freshwater resources to be dedicated to the population and their drinking water needs. "The energy cost of desalinating is three times higher than regenerating water and the CO2 footprint of desalinated water is also practically double," say sources from the Aigües de Barcelona company. During 2022, Aigües de Barcelona has regenerated 50 cubic hectometres of water, a figure that would be equivalent to the annual water consumption of more than 1 million people.
In addition to being sent to Llobregat to be made drinkable in Sant Joan Despí, reclaimed water has other uses: for irrigators in Baix Llobregat and to inject flows into the subsoil to protect the Llobregat delta aquifer; and it is also transported in vat trucks for street cleaning in eight municipalities of Baix Llobregat. There is, however, a delay in the reuse plans in the industry's distribution networks (Free Zone, El Prat...). Likewise, reclaimed water from the Gavà and Sant Feliu de Llobregat treatment plants is also used for agricultural irrigation. The metropolitan master plan for reclaimed water has planned a wide deployment of these uses, the same as the Catalan hydrological plan until 2027 throughout Catalonia.
In the context of the improvements in the Besós area, the flows of the Rec Comtal are going to be used and made drinkable, a thousand-year-old hydraulic work entering Barcelona that transports groundwater emerging from the aquifer. The goal is to use all of your available water.
From the Rec Comtal there is a channel of about four kilometers between the outcrop at the confluence of the Besòs and Ripoll rivers and its mouth in the Besòs. It transports between 500 and 600 liters per second. The problem now is that this facility runs outdoors and there is a risk of contamination. For this reason, to avoid this danger, a large pipeline is going to be built parallel to the Besòs river, so that it will link the source of the Rec Comtal and the water treatment plant. This new pipeline, which will be about six kilometers long, will be an emergency work and will run parallel to the river, in an area of public hydraulic domain, which will reduce the effects.
The Sau reservoir in the Ter is already at 14% of its maximum capacity, after having slightly recovered with the latest rains. It was emptied to a large extent due to the risk that its flows did not have the necessary quality to be used.
The Catalan Government has stressed that the situation due to drought continues to be very serious in the region of Barcelona and Girona. The forecast indicates that despite the latest rains, "if consumption is not reduced, the entry into an emergency could occur at the end of summer and beginning of autumn", reported the Government this week. The Agència Catalana de l'Aigua has explained for the first time that the average water consumption that is taking place is higher than what had been foreseen in the Drought Plan.
