Impacts of the 2021 La Palma volcanic eruption on drinking water quality (Canary Islands, Spain)

Abstract The 2021 Tajogaite eruption on La Palma, Canary Islands, disrupted groundwater systems and raised concerns regarding drinking water safety. This study evaluates post‐eruption changes in drinking water quality using an eight‐year dataset (2016–2023) of disinfected supply water sourced from groundwater, alongside complementary datasets for geology, hydrogeology and water supply infrastructure. 24 water quality parameters are analysed using an integrative framework combining nonparametric testing, municipality-scale spatial assessment, trend analysis, and interpretative evaluation. Post‐eruption changes are observed in electrical conductivity, pH, turbidity peaks, major ions, and trace metals. Among detected concentrations post-eruption, statistically significant increases are found for Hg, Cr, Cd, Sb, Cu, Mn, Al, with reductions in the percentages of samples below detection limits (% < LD) for Hg, Cd, Sb, As, Se. However, these differences are attributed to changes in data dispersion, including reduced variability, range narrowing, or high-end outliers, rather than changes in central tendency. Highest recorded levels of Se and Cr occur post-eruption; yet, parameters are largely within recommendation limits, with rare, isolated exceedances. Groundwater studies report substantial hydrochemical alterations after the Tajogaite eruption, yet no major contamination was observed in supply water. This attenuation is likely due to the selective use of unaffected water sources within the heterogeneous volcanic aquifer, combined with infrastructure-scale processes and free chlorination. These findings underscore the importance of long‐term monitoring, diversified water sourcing, and interconnected distribution infrastructure in mitigating contamination risks during volcanic events, thereby protecting public health and informing resilient water management in other volcanic island settings.