Rising water bills could become a hidden cost of climate change

Climate change could drive up household water bills across drought-prone cities by the middle of this century, according to a new study.

In one California city, researchers found the increase alone could push another seven to 16 percent of households beyond the point where water is considered affordable.

The heaviest weight lands on households that already spend far more of their income on water than anyone else.

Keeping taps reliable through hotter, drier decades means building costly new supply, and under current rules those construction bills flow straight to the people least able to absorb them.

The price of reliability

The projection comes from researchers at Stanford University, who built a model connecting regional climate change to the choices its water utility makes and the water use of individual homes.

The work was led by Jennifer Skerker at Stanford, who tested the model on Santa Cruz, a coastal city of about 96,000 in Northern California.

The city draws almost all its water from local streams and a single reservoir, which leaves it badly exposed when the rain fails.

Santa Cruz is already vulnerable. Decades of conservation have cut local water use by nearly two-thirds, so when supplies run short there is little demand left to trim.

The price of adaptation

To keep water flowing, the utility would then have to build new supply. The cheapest reliable option on the table is a desalination plant that turns seawater into drinking water.

Plants like that cost enormous sums, and utilities recover the money the only way they can, by raising rates.

“Climate change stresses water supplies, and forces utilities to build expensive new infrastructure to maintain reliability,” said Skerker.

The model tracks that chain from a dry year to a bigger bill, then follows the bill into households across the income range.

Where the burden lands

A guideline from the US Environmental Protection Agency (EPA) treats water as unaffordable once it takes up more than 2.5 percent of a household’s income.

Close to a fifth of Santa Cruz households already cross that line, a sign of how strained water affordability is before the climate changes any further.

Under the futures the model considers, that share grows to about a quarter of households under a moderate warming scenario and to more than a third in a dry one.

Typical monthly bills roughly double along the way, climbing from about $64 to $120. Heavy users would pay far more.

The strain concentrates among low-income households, who use only slightly less water than everyone else but earn far less to cover the bill.

For a family below the poverty line, water already claims close to four percent of income in the model, and a dry future pushes that above seven percent.

When costs outpace incomes

Those facing the greatest financial strain fare even worse. Among the hardest pressed tenth of poor households, water could swallow 30 percent of income, up from 16 percent today.

This level forces trade-offs between paying the water bill and covering food, rent, or medical care. None of this begins with the climate.

Water rates nationwide have climbed about three times faster than inflation over two decades, driven by aging pipes and deferred repairs.

One analysis projects that more than a third of US households could find water unaffordable within a decade on current trends. Climate stress lands on top of that.

Lessons for other cities

Santa Cruz is not most cities. It leans on a single vulnerable source, its residents have already conserved heavily, and state law limits how utilities can spread costs.

The researchers argue that it is less of an outlier and more of a preview of where other water systems may head as cheap options run out and the climate keeps tightening.

The legal piece carries real weight. A 1996 measure known as Proposition 218 limits how California utilities can design rates.

This makes it hard to charge wealthier customers more, in order to relieve poorer ones. Big infrastructure costs then tend to land on every bill at a flat rate, which hits low earners hardest.

A collision course

A separate study of El Paso, Texas, found that shrinking river flows and depleted groundwater are set to drive water costs toward unaffordable levels for the city’s poorest residents as the climate warms.

The geography differs, but the threat is the same.

Professor Sarah Fletcher at Stanford sees the trade-off as built into the system rather than incidental.

“The bottom line is that under today’s financing and regulatory models, climate adaptation and water affordability are on a collision course,” said Professor Fletcher.

The changes ahead

Until now, studies of water costs and studies of climate adaptation mostly ran on separate tracks.

Earlier work from Fletcher’s lab had shown a single drought can dent affordability for a while.

This is the first analysis to follow the steady, lasting push of a warming climate all the way to the household bill. That changes what counts as a successful climate fix.

A new plant can secure a city’s water supply and still leave thousands of residents unable to pay for it.

This is why the team argues affordability should be weighed alongside reliability rather than after it.

Making water more affordable

The fixes worth weighing sit mostly above any single utility, such as public financing for new infrastructure, changes to rate rules, or direct aid to struggling households.

“Ensuring reliable water access for everyone is going to require interventions at the state and federal level that go far beyond what individual utilities can do on their own,” said Fletcher.

What the study makes concrete is a cost that certain cities have been able to look past.

Keeping water reliable in a hotter, drier future carries a price, and without deliberate policy that price falls hardest on the households least able to bear it.

As more cities exhaust the cheap ways to conserve, the choice facing Santa Cruz between reliable water and affordable water begins to look less like a local problem and more like a national one.

The study is published in the journal Nature Sustainability.

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