- Water bills could nearly double in a hotter, drier future.
- Low-income households would face the heaviest burden.
- Researchers say local conditions shape the risk.
Wednesday, July 15, 2026 — A study published last week in Nature Sustainability
finds that climate change could make water far less affordable for many households in Santa Cruz, California.
The researchers modeled how hotter and drier conditions could affect the city’s water supply, the cost of new water projects and the bills paid by residents. Their central finding is simple: keeping water flowing during drought can require expensive new infrastructure, and those costs can show up on household bills.
In the study’s dry-climate scenario, the typical monthly water bill rose from about $64 to $120. The researchers found that the share of Santa Cruz households spending more than 2.5 percent of their income on water could rise from 19 percent today to 35 percent.
That would mean an additional 7 percent to 16 percent of households could face unaffordable water bills, depending on climate conditions and the timing of water-system investments.
Why climate change can raise water bills.
Santa Cruz receives about 95 percent of its water from local surface water, including streams and its main reservoir, Loch Lomond. The reservoir holds roughly one year of water supply. That leaves the city vulnerable when drought lasts longer or rainfall becomes less dependable.
Climate change can bring hotter temperatures, lower average rainfall and more swings between wet and dry years. Those conditions can reduce water supplies and raise demand.
Utilities have several ways to respond. They can ask customers to conserve water, improve efficiency or build new sources of supply. But Santa Cruz has already made many conservation improvements and has relatively low water use, according to the study. That means there may be fewer low-cost ways left to reduce demand.
As a result, the city could need costly projects such as desalination, water transfers, water recycling or underground water storage. The study modeled several possible projects and found that the costs of new supply can lead to higher water rates.
The burden falls hardest on lower-income households.
Lower-income households in the study generally used slightly less water and paid somewhat lower bills than other households. But their water bills took up a much larger share of their income.
Under a baseline scenario similar to current conditions, the median low-income household was already spending 3.9 percent of its income on water. That is above the 2.5 percent affordability threshold used in the study.
With new infrastructure under a moderate climate scenario, the median burden for low-income households rose to 5.1 percent. Under the dry-climate scenario, it rose to 7.3 percent.
The effects were even greater for some households. At the high end of the burden range, low-income households saw water costs rise from 16 percent to 30 percent of income in the dry-climate scenario.
The study found that smaller differences in water use do not protect households from large affordability problems when water rates rise. A household may conserve water, but a higher base charge or higher price per unit of water can still make the bill difficult to pay.
Reliability and affordability can conflict.
The research also examined three water-planning strategies. One strategy built larger infrastructure earlier to lower the risk of water shortages. It provided stronger water reliability but added at least $9.4 million per year in supply costs.
A more cautious spending strategy delayed investments and reduced added costs to $1.4 million per year. But it also produced a greater chance of serious water shortages during difficult years.
The comparison shows a difficult choice for water providers. Spending more can help protect the water supply. Spending less can reduce bill increases. Neither choice is simple when the costs are paid through customer rates.
Rainfall mattered most in the model.
Among the climate factors examined, lower average precipitation had the largest effect on affordability. More variable rainfall also raised the risk because Santa Cruz has limited ability to save water from wet years for later dry years.
Higher temperatures mattered as well. Heat can increase water use and cause more water to evaporate from the landscape. Still, the study found that supply problems were more important than changes in household demand in Santa Cruz.
Findings are specific to Santa Cruz.
The researchers caution that the results should not be treated as a forecast for every city. Santa Cruz has particular conditions that shape the outcome: limited long-term water storage, dependence on local surface water, costly supply options, existing income inequality and limits on how the utility can structure rates.
California’s Proposition 218 requires public utility rates to reflect the cost of service. The study says that rule can limit the ability to use water rates to shift more costs away from lower-income customers.
Cities with larger reservoirs, more connected water systems or access to less expensive supplies could face different results. The authors also note that their model did not include all households. It focused on single-family residential customers because individually measured water-use records for many multifamily homes were not available.
Still, the study’s broader message is that water planning is not only about having enough water. It is also about whether households can afford the steps needed to keep that water available.
Citation.
Skerker, J., Klassert, C., Francois, B. et al. Urban water affordability crisis exacerbated by climate change. Nat Sustain (2026). https://doi.org/10.1038/s41893-026-01890-z
