waterclimate

Water resources are affected by climate change, especially in the south of Europe, where droughts will be more frequent, intense, and long. In fact, Catalonia is currently facing a severe drought period of more than two years. This situation is especially critical at the Ter-Llobregat water system that is at 27% capacity as a result of 25 months of hardly any rain. Droughts have been a recurrent phenomenon in these catchments in recent years and urge the implementation of water restrictions due to the fragile balance between water demand and water supply during low rainfall periods (March et al., 2013; Quintana et al., 2019). As a result, the Barcelona City Council has developed a resilience plan to climate change, which focuses on the urban water cycle (Gonzalez et al., 2020). According to this plan, the use of alternative resources, such as groundwater, is considered to increase water availability and guarantee water supply during dry seasons.

Water management in urban areas is a priority challenge in response to increasing number pressures, however in some cases, urban groundwater resources are misused. Specifically, in Barcelona and its metropolitan area, groundwater is regularly pumped to prevent structural damage on low-lying infrastructures due to rising water tables but most of this groundwater is directly discharge into the sewerage system (Vázquez-Suñé, 2003). This is the case of several underground structures of the Besòs River Delta such as the underground parking lot of Plaça de la Vila in Sant Adrià del Besòs (Jurado et al., 2017). This underground parking lot continuously had seepage problems, and thus, groundwater pumping wells have been installed that pump a flow rate of about 150–200 L/s (i.e., 55.000-73.000 L/year). Most of the pumped groundwater is directly discharge into the sewage system and only a small amount is currently used for urban uses such as garden irrigation and cleaning the streets. The possibility to take advantage of urban groundwater is only considered when other water sources are scarce (e.g., surface water in drought periods) but thereafter urban groundwater is forgotten and rarely considered within water management schemes. Groundwater can be used as strategic resource to tackle the limited availability of surface water resources, meeting peak demands but, with this purpose in mind, it is essential to investigate the groundwater conditions and to explore its potential uses including drinking water supply.

Despite previous investigations have been conducted in metropolitan area of Barcelona regarding the groundwater resources, there are still several open questions that is needed to address to allow using this valuable resource. Within the last two decades, the Catalan Water Agency (ACA) and the Barcelona Council Authority (BCASA) have strongly committed to improve groundwater quality as a strategic resource to tackle limited availability in the metropolitan area of Barcelona. Moreover, the aquifers of the Besòs River Delta have also been the target of national and European research projects (i.e., URBANWAT, INTEGRATE, UNBIASED, FANATIC). As a result of these collaborations among researchers, public administration and water authorities, it has been concluded that the groundwater quality has declined due to anthropogenic impacts and the causes of the deterioration have to be quantified. This point is critical to assess the potential uses of groundwater and to forecast potential future scenarios.

In this context, it is of paramount importance to develop innovative tools to properly manage the groundwater resources in urban areas, define best water practices and the efficient management of water resources under the current context of climate change. These tools include approaches for the identification and quantification of recharge sources into aquifers through source apportioning using environmental isotopes and contaminants of emerging concern (CECs) and coupled hydro-chemical numerical models to predict the groundwater behaviour under different scenarios.