The latest work centred on extending the network on the mountain of Montjuïc, where the civil engineering project has now been completed to construct three new tanks at Castell de Montjuïc (1,200 m³), Viver de Tres Pins (600 m³) and the Jardins de Joan Brossa (600 m³). The calculations are that between them the availability of groundwater should rise by 50,000 m³ a year.

The tank at the castle is the largest of the three. Owing to its location, and with the goal of minimising the visual impact in the natural environment, access to the dry chamber in the tank and the ventilation system have been designed with a horizontal shaft roughly 65 metres long and two metres in diameter. The specific geological conditions of Montjuïc and the presence of very dense rock made this a very complex excavation. In all, the works implemented in Montjuïc entailed an investment of 10.9 million euros.

The groundwater system on Montjuïc completes the work to extend the network in other areas of the city. Work carried out at Can Batlló and in different points of L’Eixample were completed at the end of 2025, in addition to the installations executed previously at Alfons el Magnànim and Palau Reial.

The investment in enlarging the groundwater network means that it now reaches 186 hectares of greenery watered with groundwater, representing a saving in safe water used for this purpose.

The use of alternative water resources for municipal activities such as watering green spaces, cleaning streets and sewerage and supplying decorative fountains significantly reduces the consumption of safe water, an increasingly scarce and valuable resource, particularly during times of drought, As a result, the extension of the groundwater network helps to adapt and prepare the city to climate change challenges, one of the goals of the Climate Plan.