Climate Change and Drinking-Water Quality from Catchment to Tap: A Critical Review

Climate change is altering the quality of surface water and groundwater used for drinking-water production, while also challenging treatment processes and distribution-system stability. This review synthesises evidence across the catchment-to-tap continuum, framing water quality within the coupled changes in water quantity, land use, and demand that accompany climate change. Warming, drought, intense rainfall, flooding, wildfire, and sea-level rise can increase turbidity, salinity, natural organic matter, nutrients, pathogens, cyanobacteria, metals, and organic micropollutants, while compound events may cause abrupt contaminant pulses coinciding with infrastructure failures. Beyond summarising element-level evidence, the review makes four specific contributions: (i) a review of reviews that grades the strength of evidence for each contaminant group and identifies the interfaces between catchment, treatment, and distribution left unaddressed by previous reviews; (ii) the identification of common-cause failures, whereby a single climatic driver weakens several barriers simultaneously, contrary to the independence assumed in multi-barrier design; (iii) a distinction between short-term variability, which existing practice can absorb, and a persistent shift to a new climatic normal, which erodes seasonal recovery windows and turns episodic responses into structural costs; and (iv) a compilation of indicative quantitative thresholds for these transitions. Priority adaptation measures for resource-limited systems and the main open research questions are also identified.