Association of drought conditions and heavy rainfalls with the quality of drinking water in Barcelona (2010-2022).

Abstract

Climate change influences the incidence and scope of climate extreme events that affect communities and the environment around the world. In an urban context such as Barcelona, these climate extremes can have a negative impact on drinking water quality. The worsening of drinking water quality can have important repercussions on human health, leading to the appearance of different diseases. Investigate the association between climate extremes, in particular heavy rainfall events and drought conditions, and the drinking water quality in the city of Barcelona from 2010 to 2022. We conducted a daily retrospective time-series study using data covering 13 years of daily monitoring of conductivity, nickel, turbidity and trihalomethanes parameters of raw water in the Llobregat River catchment area and treated water in the Drinking Water Treatment Plant (DWTP) Sant Joan Despí. We used river flow as a proxy for drought conditions and heavy rainfall events. We analyzed short-term associations between river flow rate and quality parameters in raw and treated water using generalized linear regression with distributed lag-non-linear models (DLNM). A low flow, as an indicator of drought condition or low rainfall, was significantly associated with an increase in conductivity in raw water and nickel in both raw and treated water. A high flow, as an indicator of heavy rainfall events, was significantly associated with an increase of turbidity in raw water, and a decrease in all other quality parameters. This study provides novel evidence that climate extremes have an impact on the quality of drinking water in urban areas with a Mediterranean climate. The findings of this study are significant because they suggest that as the frequency and intensity of climate extremes increase due to climate change, there will be further challenges in managing and treating drinking water, which could have a detrimental effect on public health. This study serves as an important reminder of the need to strengthen and accelerate adaptation actions in water management to ensure an adequate supply of drinking water that protects the people's health.