Researchers find rising infrastructure costs and water scarcity could make household water less affordable, with low-income families facing the greatest burden.
Climate change could dramatically increase household water bills in cities vulnerable to drought, with some urban communities facing nearly double today’s costs by the middle of the century, according to a new study published in the journal Nature Sustainability on July 8, 2026.
The study is the first to comprehensively examine how climate change, aging infrastructure, utility investment decisions and household water demand interact to shape water affordability. While previous research has largely focused on water system reliability and infrastructure costs, the new analysis assesses how those rising costs could affect households across different income levels.
The researchers conclude that adapting urban water systems to a changing climate will require more than action by local water utilities. They call for broader regulatory reforms, increased public investment in climate-resilient infrastructure and targeted financial support for vulnerable households.
RELEVANT SUSTAINABLE GOALS
Climate Adaptation Could Nearly Double Household Water Bills
To understand how climate change could affect water affordability, researchers used Santa Cruz, California, as a case study.
The coastal city relies on limited local water supplies and has already implemented many of its lowest-cost conservation measures. As water scarcity intensifies, the city’s remaining options to improve long-term water security include expensive infrastructure projects such as desalination plants and wastewater reuse systems.
Using a modelling framework developed with data from Santa Cruz’s water department, researchers found that climate change alone could leave an additional 7% to 16% of households facing unaffordable water bills.
By mid-century, adapting to worsening water shortages could nearly double the city’s median household water bills.
Low-Income Households Face the Greatest Financial Pressure
The study found that approximately 19% of Santa Cruz households already spend more on water than the affordability threshold established by the U.S. Environmental Protection Agency (EPA).
Under a moderate climate scenario, that figure could rise to 26%. In a drier climate requiring additional investments to secure reliable water supplies, the proportion could increase further to 35%. The burden would fall most heavily on lower-income residents.
Under the study’s most severe dry-climate scenario, the median monthly water bill for the city’s poorest households would increase from approximately US$60 to US$111.
More than 5% of households could ultimately spend nearly one-third of their income on water, forcing difficult choices between paying for water, food, healthcare and other essential needs.
Water Security Comes With Difficult Cost Trade-Offs
The researchers also identified significant trade-offs between improving water security and maintaining affordable household bills.
Constructing large desalination facilities earlier would strengthen water supplies during droughts but would substantially increase water bills.
Delaying major infrastructure investments would lower short-term household costs but leave communities more vulnerable to water shortages during future drought years.
The findings highlight the growing financial challenges cities face as they attempt to build more resilient water systems under changing climate conditions.
Aging Infrastructure and Climate Change Drive Rising Costs
Water prices have already been increasing across the United States.
According to the study, the average cost of tap water has risen three times faster than inflation over the past two decades, largely because of aging infrastructure and years of delayed maintenance.
Climate change is now adding further pressure by increasing the need for costly infrastructure upgrades and expanded water management measures.
Researchers identified drought and declining water availability as the greatest threats to urban water systems.
Higher temperatures and changing rainfall patterns are making droughts more frequent and severe, reducing the reliability of traditional water sources and increasing pressure on cities to invest in alternative supplies.
Lessons Extend Beyond California
Although the study focused on Santa Cruz, researchers say the modelling framework can be applied to many other climate-vulnerable cities facing similar water challenges.
These include Los Angeles, San Diego and San Francisco in the United States, Cape Town in South Africa and Melbourne in Australia.
South Africa receives approximately 464 millimetres of rainfall annually—less than half the global average—making it one of the world’s driest countries.
In 2018, Cape Town came close to exhausting its municipal water supply, prompting authorities to limit residents to 50 litres of water per person each day. Strict conservation measures and water rationing ultimately helped the city avoid the widely anticipated “Day Zero.”
Melbourne is also experiencing increasing water stress. Between March 1 and June 1, 2026, reservoir storage declined by 6.1%, equivalent to 111 billion litres of water.
Current storage levels are 9.5% lower than a year earlier and 24% below levels recorded two years ago, reflecting prolonged dry conditions, record-low inflows and growing water demand.
According to the researchers, these examples demonstrate how climate change is intensifying water shortages while increasing the financial cost of maintaining reliable urban water systems.
Study Calls for Climate-Resilient Water Policies
The researchers conclude that addressing climate-driven water affordability will require coordinated action beyond local water utilities.
They recommend regulatory reforms, greater public investment in climate-resilient water infrastructure and targeted financial assistance for households most vulnerable to rising water costs.
The study also urges policymakers to include water affordability alongside supply reliability when planning future climate adaptation strategies.
By evaluating both infrastructure resilience and household affordability together, the researchers argue that cities can better prepare for climate change while reducing the risk that adaptation costs disproportionately affect lower-income communities.
