Climate change threatens urban water affordability

Climate change increases water stress in many regions globally, necessitating expensive infrastructure investments to maintain reliable supplies. To fund infrastructure, utilities often raise rates, increasing water bills for low-income households. The magnitude of resulting impacts on affordable water access depends not only on utility costs but also interactions between infrastructure financing, rate design, climate, and household water use patterns. Here, we develop a modeling framework to comprehensively measure climate impacts on urban water affordability, integrating climate, infrastructure, and social dynamics. We apply our framework in Santa Cruz, California, where, like much of the American West, growing water stress and income inequality threaten water affordability. We find that climate change could double water bills, leaving more than one third of households with unaffordable water. Additionally, half of all low-income households could pay nearly 7.5 percent of their income on water bills, three times the EPA’s recommended threshold. This highlights the need to design climate adaptation without compromising affordability. While the mechanisms that drive climate change impacts on affordability are generalizable, their magnitude depends on local environmental, infrastructure, and social factors, necessitating city-scale assessments.