Barcelona Metropolis

The dwindling water reserves is pushing us towards a necessary water transition that must be approached from multiple perspectives. Regenerated and desalinated water cannot be the only solution: we must explore alternative resources, such as greywater reuse, while acknowledging the role of water in urban greenery as heat refuges. All of this must be done without losing sight of vulnerable populations, who should not bear the burden of additional costs.

In recent years, Catalonia’s internal river basins have suffered the worst drought in a century. The Ter-Llobregat system, which supplies water to the Barcelona metropolitan region, bore the brunt of climate change between 2021 and 2023. The system entered a state of drought emergency in early 2024, when water reserves in the Ter and Llobregat reservoirs dropped below 100 hm³ – just 16% of their total capacity.

At the Fabra Observatory in Barcelona, rainfall anomalies of 50% were recorded for three consecutive years, from 2021 to 2023, while average temperatures reached record highs, particularly in 2022 and 2023, with anomalies close to 3°C. All evidence suggests that the climate emergency is reshaping hydroclimatic risks, with the western Mediterranean coast emerging as one of the regions on the front line of global change.

In 2023, much of Catalonia’s internal river basins were among the first to be placed on drought alert and exceptional status. The Ter-Llobregat system, along with other subsystems, was officially declared in a state of emergency at the start of 2024. This prompted the Agència Catalana de l’Aigua [Catalan Water Agency] to tighten restrictions already in place during alert and exceptional phases, particularly for the primary sector – the hardest hit by the drought – with irrigation cut by 80% and water use in livestock farming reduced by 50%. Urban and domestic water use was also affected, with a ban on watering green spaces and public or private gardens, except in exceptional cases to ensure the survival of public trees, and only if groundwater or regenerated water was used.

The city of Barcelona, along with most of its metropolitan area, set an exemplary standard by not exceeding the allocation of 200 litres per person per day – a figure that includes economic and commercial activities, as well as domestic and urban uses – as stipulated by the Drought Plan. The extreme severity of the rainfall deficit was alleviated by the concerted efforts of citizens, various economic sectors and resource management authorities, from the local to the basin level. It is also crucial to recognise the vital role that non-conventional water sources have played – and will continue to play – in this new normal.

Despite the substantial improvement in the situation from the second half of 2024, due to a more normalised rainfall pattern, the extreme severity of the drought episode is far from overcome. This has sparked a series of debates that should inform the agenda for a water transition that guarantees sustainability and water security in the metropolitan area, as well as in the internal basins, within the context of the climate emergency.

New climate scenarios indicate a general trend towards decreasing rainfall and greater temporal concentration, leading us to consider that the drought we are experiencing may be structural, requiring us to adapt to this new water normality. The following reflections address this reconfiguration of water management, from the role of centralised and decentralised alternative resources to water’s essential role in mitigating the impacts of the climate emergency, particularly in the form of heatwaves.

The key role of regenerated water in the metropolitan hydrosocial cycle

The drought has accelerated large-scale infrastructural interventions aimed at reshaping the hydrosocial cycle of the metropolitan region, enhancing its resilience to the impacts of the climate emergency and reducing its dependence on water levels in the Ter-Llobregat reservoir system.

The opening of the El Prat desalination plant in 2009, one of the largest in Europe, was initially seen as a solution to the vulnerability of the metropolitan water system following the drought of 2007 and 2008. However, in the face of the most severe meteorological drought in over a century, with desalination plants operating at full capacity, the indirect reuse of regenerated water for potable purposes has emerged as the new frontier of metropolitan water management.

The metropolitan stretch of the Llobregat River lies at the heart of this major transformation, while the Besòs is expected to complete its transition by becoming the metropolitan area’s new water source, following the Llobregat’s water regeneration model. While recognising the merits and potential of these new resources (including the additional desalination plants planned by the Generalitat Government of Catalonia), it is essential to avoid an uncritical perspective or unfounded technological optimism about the capacity to generate new water flows immune to the vagaries of climate change.

Firstly, assuming that such infrastructures will free us from climatic constraints may result in inadequate societal adaptation to the climate emergency, hindering the necessary reconfiguration of the metropolitan water metabolism. Secondly, as will be discussed later, the water transition will inevitably lead to higher resource prices, making it essential to ensure that cost distribution does not disproportionately affect the most vulnerable groups. Lastly, these alternatives are unlikely to provide solutions for the sectors hardest hit by the drought –strategic sectors such as agriculture and livestock, as well as forest and river ecosystems.

To promote alternative resources on a local scale

The reuse of greywater is, at the same time, an example of decentralised water management driven by citizens. Over the past two decades, dozens of local water-saving regulations have been approved in the province of Barcelona. Many of these regulations, beyond setting out requirements for new buildings, seek to make the use of non-potable water compulsory. This includes using greywater from showers and bathtubs to flush toilets, as well as rainwater and leftover water from cleaning pool filters for watering gardens and cleaning surfaces.

In 2005, Barcelona Provincial Council published a model water-saving bylaw which, together with the successful experience of the municipality of Sant Cugat del Vallès – which has had an ordinance since 2002 – has shaped the trajectory of many subsequent regulations. Following these examples, and as the Provincial Council prepares to update its model water-saving bylaw, Barcelona City Council gave initial approval in February 2025 to its Greywater Ordinance. This regulation set the thresholds for compulsory greywater reuse (from showers and bathtubs) to flush toilets, both in new buildings and in comprehensive renovations. It is expected to save up to 136,000 m³ of potable water annually.

Guaranteeing the human right to water and preventing water insecurity must be key pillars of adaptation to a future marked by more frequent heatwaves. At the same time, efforts to promote water efficiency improvements at the household and building scale must follow principles that ensure these upgrades are accessible to the most vulnerable groups – connecting with the broader, sensitive debate on access to housing in the city. Public administrations have a crucial role in supporting residents, particularly the most vulnerable, to enable a sustainable and just water transition. Water efficiency should not be a privilege but a right – one that could also help offset rising water bills for the most vulnerable households. At the same time, this water transition should avoid utilitarian and anthropocentric visions, bringing to the table the need to rethink our interdependencies with river ecosystems.

References

“El Govern fixa el calendari de les mesures que permetran disposar de més aigua”. Generalitat Government of Catalonia, October 2024. via.bcn/Vl9850V3j8q

March, H., Gorostiza, S. and Saurí, D. “Redrawing the hydrosocial cycle through treated wastewater reuse in the metropolitan area of Barcelona”. Water Alternatives, 16(2), 463-479. 2023.

March, H. and Saurí, D. “When sustainable may not mean just: a critical interpretation of urban water consumption decline in Barcelona”. Local Environment, 22(5), 523-535. 2016.

Romero-Gomez, G., Nadal, J. and Saurí, D. “Experiences of water poverty in the metropolitan area of Barcelona: implications for the Global North”. Journal of Water, Sanitation and Hygiene for Development, 14(9), 819-832. 2024.

Barcelona City Council. Aprovació inicial de l’Ordenança d’aigües grises de Barcelona, 2025. via.bcn/gls250V43RP