How Portland gets its drinking water

Jan 20, 2024

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PORTLAND, Ore. — Portland residents could be forgiven for not knowing a ton about where their drinking water comes from.

It's an easy thing to take for granted – you turn the tap and out comes cool, clear, clean water.

But there's a lot that happens between when a drop of rain falls in the Cascades and you’re able to fill up a glass at home.

"Water systems are mostly pretty invisible for those of us who rely on it every day," said Sarah Murphy Santner, Resource Protection & Planning Director at the Portland Water Bureau. "It's nice to take a moment to really think about where your water comes from."

Portland has two primary water sources: the Bull Run Watershed and the Columbia South Shore Well field.

Less than 30 miles from downtown Portland, the Bull Run Watershed is a 102-square mile temperate forest on the western flank of Mount Hood that sees more than 130 inches of rain per year. For comparison, Portland averages around 37 inches of rain per year.

All that rain that falls on the watershed drains through creeks, streams and rivers into two reservoirs, which together hold nearly 17 billion gallons of water, with nearly 10 billion gallons available for drinking water.

The city operates two dams, with the first layer of treatment – chlorine – at the intake. Gravity carries the water through another treatment facility where sodium carbonate and carbon dioxide are added, before the water flows into covered reservoirs at Powell Butte, Kelly Butte and in Washington Park.

From there, the water flows into smaller holding tanks and pipes before entering the final leg of the journey to Portland homes and businesses: the 2,200 miles of distribution pipes under city streets.

"Water is really the backbone of a healthy community," Santner said. "It's the backbone of a healthy economy."

With something as important as drinking water, redundancies are important. The city has a secondary water source in the Columbia South Shore Well Field, 25 wells east of the Portland International Airport capable of producing up to 95 million gallons per day.

That isn't quite enough to meet peak summer demand, which can top out at 150 million gallons per day, but the well field, which pulls from aquifers deep underground, acts as a failsafe should something go wrong with the Bull Run system.

But even having redundancies doesn't mean there aren't things that keep Santner up at night.

"With climate change, we are seeing increased pressures on our water supplies," she said.

Western Oregon has typically seen no shortage of precipitation, and even climate models expect that to continue. But when and how that precipitation falls is expected to change as the climate warms, with more coming as rain than snow and more frequent deluges and less predictability.

But beyond the long-term changes a warming climate will bring, Santner has other, more acute concerns.

"I think the thing that keeps me up at night is just the inevitability of some sort of major catastrophe, whether it's an earthquake or a wildfire, something eventually might come and damage the water supply system," she said. "The thing I worry the most about is how our community is prepared to manage for a few days or a few weeks without water."

The best way to do that, she said, is to be prepared. Experts recommend storing a gallon of water, per person, per day, in a safe place it will be accessible in an emergency.

The biggest day-to-day concern is with the age of Portland's water system. The Bull Run system was established in 1895 and the average age of the city's distribution pipes is around 70, with the oldest pipe in the system nearing its 130th birthday.

The water bureau recently proposed a 6.6% increase in water and sewer services.

"I think the most important thing for Portlanders to understand about the water system is that it's old," Santner said. "We've had a system in place for many, many years, and that system needs ongoing maintenance and that maintenance unfortunately costs money."

But at least you’re getting what you pay for, Santner said, noting that Portland's water has consistently placed well in taste and quality tests.

"It's fantastic quality and you know when you travel from afar and you come here, we often get comments from folks out in the world or saying, 'Wow, this water tastes really good,'" she said.

If you want to learn more about Portland's drinking water system, the water bureau is hosting an informational bike ride Saturday, May 13, to tour the well field.

Doug Wise, groundwater protection program manager, said the water bureau is excited to get back to in-person events after several years.

"We'll take folks to a couple of supply well sites," Wise said. "We'll take them to our central groundwater pump station where all the magic happens, and we lift all that water 500 feet up to the reservoirs at Powell Butte so that we can deliver it to our customers."

The 17-mile ride will start at 8:45 a.m., but space is limited, and registration is required.