Global warming could make running water much more expensive in some cities. A study conducted in Santa Cruz, California, estimates that hotter and drier periods could almost double the median bill by mid-century. The risk mainly concerns already vulnerable households.
The studied city depends almost entirely on local resources and a single reservoir. When rainfall decreases, managers must preserve the supply. However, the most resilient solutions, such as wastewater reuse or desalination, require costly investments.
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The researchers linked in a single model the climate scenarios, infrastructure choices, the rates applied by the water service, and household consumption. This approach makes it possible to study not only the amount of water available, but also how its cost is distributed among residents.
In the dry scenario retained, the median bill could almost double in Santa Cruz. The share of households exceeding the affordability threshold recommended by the United States Environmental Protection Agency would go from 19% to 35%.
The poorest households would, unsurprisingly, be the most exposed. The model estimates that their average monthly expense could go from about 60 dollars to 111 dollars, in current value. For some households, water would then represent a significant share of disposable income.
Adaptation choices create a difficult trade-off. Building large desalination capacities early improves supply security, but immediately increases bills. Delaying investments limits immediate costs, while increasing the risk of restrictions during droughts.