Increasingly less water: Barcelona will need additional water resources

Water is an essential element for the functioning of both natural ecosystems and urban systems. In the Mediterranean environment water is becoming an ever more scarce and extremely precious resource, as the Mediterranean climate is characterised by the combination of a fairly long summer drought with great interannual variability in precipitation, the dry season coinciding with the warm season, the season in which water is needed most. These facts necessitate the comprehensive management of water resources, understanding the complexity of its entire cycle in order to try to respond to the multiple needs of natural ecosystems and urban systems.

Every year 200 hm3 of water (80,000 Olympic swimming pools) enters Barcelona in the form of drinking water, rainwater or local extraction from groundwater. However, the city currently has a deficit in its water supply system, as the resources are less than, or very close to, the level of demand one year out of every four. At the moment this is being resolved with the reservoir reserves of previous years, but the guaranteed supply is only one year.

The effect that climate change could have on the water cycle, as the various projections seem to indicate, is a decrease in water resources and a greater variability in their availability, which would increase drought periods. On the other hand, a slight increase in demand is also predicted, due to population growth in the middle of the century.

The water cycle in Barcelona and its surroundings

Barcelona and its metropolitan area are home to a large part of the population and economic activity. It therefore has water needs that cannot be covered by water resources from its immediate surroundings (end of the Llobregat and Besòs basin). Therefore, a significant part of the drinking water supply is currently supplied using resources from external basins. The other types of water that complete and form the water cycle in the city are groundwater, desalinated water, rainwater, wastewater and reclaimed water.

Drinking water

Drinking water that enters Barcelona forms part of a huge interconnected supply network called the Ter-Llobregat system network (ATLL network). The ATLL network is mainly supplied with surface water from the Llobregat and Ter river basins. Underground water also enters from the Llobregat delta (and, to a lesser extent, from the river Besòs). Finally, a smaller amount of the drinking water is taken from the sea and desalinated.

Drinking water supply network upstream of the Ter-Llobregat System. Source: Ter-Llobregat Water website (ATLL, 2017)

Due to the significant demand concentrated there, management of the Ter and Llobregat river reservoirs is carried out jointly, and depending on the reserves of the surface resources, the other resources that complement the network are managed (ground and desalinated water) with the aim of maintaining the water in the reservoirs for as long as possible. From January 2018, rules of coordinated operation have been applied to the Ter-Llobregat network according to the Special Action Plan for Situations of Alert and Potential Drought (PES) (pending final approval), drafted by the Catalan Water Agency (ACA), which establishes various actions according to the defined scenarios.

Evolution of the types of water resource supplying the metropolitan area. Source: AMB

Production of drinking water in the Ter-Llobregat network (multi-annual averages). Source: ACA

The irregularity of the Mediterranean rainfall system has meant that over the last 30 years the reserves of the Ter-Llobregat system have been below the drought alert limit, historically situated at 250 hm3, 20% of the time.

Evolution Ter-Llobregat System (1982-2018) with scenarios from the PES

Rainwater

The natural inflow of rainwater varies year on year due to the variable climate of the area. This makes it a resource that is available at certain, very variable times, making it difficult to take advantage of.

The majority of rainwater becomes run-off water that is collected in the city’s sewerage system. Rainwater also irrigates the city’s green zones or tops up the aquifer through the permeable zones.

On the other hand, a significant amount of rainwater returns to the atmosphere through evapotranspiration.

Groundwater (for non-potable uses)

Much of the groundwater extraction for non-potable uses is from private wells, mainly for industrial uses (for example, the Zona Franca industrial estate). However, there is also a network of municipally-owned wells that extract water for irrigating green spaces, street cleaning, ornamental fountains and municipal facilities. Finally, a considerable amount of groundwater is extracted at various points in the metro network, to prevent the aquifer from damaging the facilities.

Waste water

Wastewater is the main outlet for water in the urban water cycle. This is collected by the sewerage network and transported to the wastewater treatment plant (WWTP) at Besòs, Llobregat and, to a lesser extent, Vallvidrera, where it is treated.

The water that arrives at the WWTP is, in dry periods, wastewater or water used by the domestic, industrial and municipal sectors, and in rainy periods, a mixture of wastewater and rainwater that enters the sewerage system.

Reclaimed water

Wastewater treated at the WWTP returns to its natural cycle and is discharged into the receiving environment through special channels or undersea pipes, taking care not to alter natural systems, or it undergoes additional treatment in a water reclamation plant (WRP) that allows it to achieve the appropriate physicochemical and sanitary quality for it to be reused as reclaimed water.


Reclaimed water may be used as a saline barrier, for environmental purposes in rivers, for agricultural irrigation, for maintaining wetlands and for industrial purposes.


In the territorial context of Barcelona, industrial uses have great potential as, due to their proximity, the businesses located at the Zona Franca industrial estate can be significant consumers of reclaimed water in processes that do not require the quality of drinking water.

Demand and consumption in the Barcelona urban system

The domestic sector has the highest consumption of water in the city of Barcelona, representing 38.2% of the total. The domestic sector only consumes drinking water. The commercial and industrial sector comes second, representing 22.9%. In this instance, however, as well as using some drinking water, a large amount of the demand is also covered by groundwater. In third place, at 21.8%, there is water that goes to the public space, which includes both run-off rainwater and water used to clean the streets.

Total water consumption for different needs (2012). Source: Barcelona Regional

Analysing the evolution of the main water consumption sectors (domestic and commercial/industrial and municipal) shows a reduction in drinking water consumption in all these sectors. But especially noteworthy is the 17% reduction in the domestic sector, where, over the years, the raising of awareness among the population has played a very important role, reaching a relatively low per capita consumption of about 107 litres per inhabitant and day during 2018 (the WHO establishes that the minimum required limit is 100 l/inhabitant/day). In this regard, one of the strategic goals of the Climate Plan for 2030 is to achieve a consumption of domestic drinking water of less than 100 l/inhabitant/day.

Evolution of Barcelona's water consumption by sector Source: Barcelona Regional

Evolution of domestic consumption per inhabitant and per day: Source: Barcelona Regional

Based on consumption weighted by type of housing, the following map shows the consumption per inhabitant per neighbourhood. Some neighbourhoods have a consumption well above the city average in terms of population, as is the case of the neighbourhoods of Pedralbes, Sant Gervasi-la Bonanova, Tres Torres, and Vallvidrera, el Tibidabo i les Planes However, the neighbourhoods with lower per capita consumption are mainly in the districts of Nou Barris, Sant Andreu, Horta-Guinardó and Sants.

Water consumption per inhabitant and per neighbourhood (l/inhabitant*day) Source: Barcelona Regional

Municipal powers

Barcelona City Council does not exercise power over drinking water supply directly, though it can take part in better water management in a general sense or in the event of a drought, by reducing superfluous municipal consumption or running campaigns and raising awareness among users. Together with the Generalitat de Catalunya, the City Council also acts as a health authority that monitors the quality of piped water through the Barcelona Public Health Agency (ASPB). Moreover, through the Environment and Urban Services - Urban Ecology and thanks to a grant from the ACA, the City Council is responsible for managing groundwater obtained from the city's subsoil for retail supply for permitted municipal purposes (supply without the use of entrance).

The water cycle in the current situation

Current needs and consumption of water in Barcelona.

In 2012, 197 hm3 of water entered the city in the form of drinking water, rainwater and local groundwater extraction. In terms of water leaving the city, the main channels are wastewater, rainwater run-off and evapotranspiration.

Origin of water inlets to Barcelona's urban system (2012). Source: Barcelona Regional

See below a general diagram of the main inlets and outlets in the Barcelona water cycle (data from 2012).

General diagram of the current water cycle (2012) Source: Barcelona Regional

Climate change in the water cycle

The impact of climate change on the water cycle has been analysed for the committed scenario, corresponding to the fact that global emissions will be reduced according to the Paris agreements (scenario RCP4.5) and for the middle of the century. For 2050 the following is predicted:

• A 4% increase in the need for drinking water.
• A 12% reduction in surface resources from the Ter and Llobregat basins.
• A 9% reduction in groundwater resources in the Llobregat basin, Besòs and local aquifers.

There will therefore be a general need for additional potable water resources in the metropolitan area of 34 hm3 a year, with the city of Barcelona’s need estimated at 18 hm3 a year.

See below the water cycle in Barcelona projected for 2050.

General diagram of the water cycle in the committed scenario (2050) Source: Barcelona Regional

Adaptive capacity

Given the prospect of a decrease in water resources, greater variability and a slight increase in demand, it is important to predict the possible effects of climate change, anticipate them and implement the necessary adaptive measures to focus on the possible changes with a greater degree of resilience.

Currently, water supply in Barcelona and the metropolitan area depends on the ATLL network, which is mainly based on making use of surface water resources, largely from external basins. It is necessary to reconsider the entire water cycle with more efficient, diversified and sustainable management of the water resources.

Barcelona City Council already has various plans and actions mainly focused on managing demand, implementing technological efficiency measures and including alternative water resources. New multifunctional initiatives in this area are currently being worked on and promoted, on different scales, within their competence framework.

In 2020, final approval of the new edition of Barcelona's Technical Plan for Harnessing Alternative Water Resources (PLARHAB) is expected. It aims to progressively replace the consumption of potable water with the use of alternative hydrological resources, including groundwater, reclaimed water, rainwater from run-off and roofs, greywater and seawater in cases that do not require drinking-water quality.

This Plan has also carried out an analysis of the characteristics and features of the various kinds of non-potable water, and has also analysed the quality requirements of the different uses. It also lays the foundations for the creation of a future byelaw regulating the use of alternative water resources in the city.

In 2018 Barcelona City Council approved the Action Protocol for risk of drought in the city of Barcelona (annexed to the Municipal Civil Defence Plan [PPCM]), which aims to prevent and anticipate possible drought situations, establishing preventative measures and defining an action model of municipal services when there is a drought situation in the city. This protocol is part of the Catalan Water Agency’s Special Action Plan for Situations of Alert and Potential Drought (PES) (pending final approval). It establishes various corrective measures organised according to the scenarios defined in the PES, consisting of actions to raise awareness and communicate to the public and specific actions to save water in services or activities that generate more consumption.

The PLARHAB, the PPCM - Protocol for drought situations, and the Climate Plan set out a series of actions to try to reduce pressure on the demand for drinking water and make the water cycle more efficient, for example:
1. Encourage water saving in the domestic sphere through communication campaigns.
2. Use groundwater for all municipal uses that do not require high quality drinking water (+2,7 hm3).

Current groundwater network and improvement and adaptation actions. Source: Technical Plan for Taking Advantage of Alternative Water Resources in Barcelona (2020) Barcelona City Council

3. Use reclaimed water for industrial uses(+5 hm³).
4. Protect Barcelona’s underground water veins, boosting infiltration in spaces that are permeable and do not have a use of subsoil.
5. Make use of the Besòs aquifer groundwater resource as drinking water (+12 hm³/year).

Aquifers in Barcelona and the surrounding areas. Source: Barcelona Regional, based on information from the Catalan Water Agency

6. Promote the use of greywater in new housing developments or in renovations (+1,3 hm³).

Consumption in the home. Source: Barcelona Regional

7. Apply sustainability principles with the saving and responsible and efficient use of water.
8. Make use of rainwater: collection and use of rainwater and promotion of sustainable urban drainage systems (SUDS).
By jointly analysing the series of proposed measures, it is possible to make up for the additional volume of drinking water through actions that reduce the pressure on the demand for drinking water in the uses that do not require it and with the use of local resources to generate it.
Therefore, the 18 hm3 initially estimated could be covered by adopting the proposed measures, which would be approximately 21 hm³. If the planned measures are taken, they could counteract the effect of the reduction in water resources associated with climate change.