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Drought-resistant Pendleton still sees dwindling groundwater supply

Aquifer storage and recovery system has reduced impact on groundwater, but the level keeps dropping
Antonio Sierra

East Oregonian

Published on October 6, 2017 10:42AM

Staff photo by E.J. Harris
The intake for the City of Pendleton’s aquifer recharge system takes water from the Umatilla River during higher rates of flow east of Pendleton.

Staff photo by E.J. Harris The intake for the City of Pendleton’s aquifer recharge system takes water from the Umatilla River during higher rates of flow east of Pendleton.

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Staff photo by E.J. Harris
The water pressure for the City of Pendleton’s well water system reads on a pressure gauge at city well 14 on the west side of Pendleton. The city currently operates eight wells for its drinking water system.

Staff photo by E.J. Harris The water pressure for the City of Pendleton’s well water system reads on a pressure gauge at city well 14 on the west side of Pendleton. The city currently operates eight wells for its drinking water system.

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Pendleton’s aquifer storage and recovery system has won plaudits from the state and been a crowning achievement for the city’s public works director, but it isn’t a silver bullet.

Despite the innovative system that allows Pendleton to funnel most of its drinking water from the Umatilla River rather than pumping it from the ground, the city’s groundwater supply has still dwindled over the years.

The numbers fluctuate depending on whether it has been a wet or dry winter, but Public Works Director Bob Patterson said groundwater levels have dropped an average of 1.4 feet per year for the past 14 years since the ASR went online.

That’s better than the average 3.5 feet per year decrease before. But the new system isn’t consistently preventing groundwater loss, much less recharging the aquifer.

Groundwater depletion is often discussed in an agricultural context in Oregon, but cities across the arid Eastern Oregon landscape rely on the same supply.

If the area can’t stop drawing heavily from the aquifer, Patterson’s prediction is dire.

“At some point, someone’s going to go dry,” he said.

It’s just a matter of where and when.

Deepening wells

Patterson, whose work in the development of Pendleton’s ASR system earned him a spot on the 2016 Top Ten Public Works Leaders by the American Public Works Association, compared extracting groundwater to straws in a bowl.

Pendleton has eight straws in the bowl — wells that pump 8.5 million gallons of water per day during peak use.

The city eases its groundwater consumption by drawing water directly from the river during the winter and spring, treating it and storing it at the water filtration plant in east Pendleton.

Utilizing micro-turbines that power five wells and a first-of-its-kind siphon design used for water filtration, the city has stored billions of gallons of water in a drought-plagued region that averages just 12 inches of rain per year.

On balance, the city now draws 100 percent of its supply from water stored from the cooler months, although it still draws groundwater as a back-up for especially dry years. Since ASR was started in 2003, the city has left an estimated 8 billion gallons of water in the ground.

In 2007, the city won Stewardship and Conservation Award from the Water Resources Commission for its ARS system.

But it isn’t enough to stop groundwater declines.

When a production well in Roy Raley Park went down in August, part of the issue was that the pump was having difficulty lowering further down the 700-foot hole. If the pump wasn’t allowed to lower from 400 feet down to 440 feet, it was in danger of eventually pumping air.

There’s other data that show a decline in groundwater in the Pendleton area. According to the Oregon Water Resources Department, most of the observation wells in the area show a steady decline from about 900 feet average mean above sea level in the 1950s and 1960s to 800 feet in 2015. In 2016, The Oregonian calculated that the Umatilla Basin, which covers Pendleton and most of Umatilla County, is at 148 percent capacity, meaning there was far more usage than replenishment.

The Umatilla Basin is a part of the larger Columbia River Basalt, a geological formation formed from more than 150 layers of cooled lava flow covering Oregon and Washington.

The water that seeped between those layers forms the basis for the basin’s groundwater, but because of the region’s sparse rainfall and the slow flow of snowmelt from the Blue Mountains, the aquifer recharges slowly.

With Pendleton’s ASR system already in place, Patterson said farmers on the west side of the county, where irrigated agriculture is the most prevalent, were the cause of the cross-county decline. Patterson said adoption of ASR or better conservation techniques by farmers could help stem the decline.

Different solution

Everyone who relies on groundwater agrees that the decline needs to be addressed. But how it’s done is up for debate.

J.R. Cook, the director of the Northeast Oregon Water Association, said there’s no definitive proof that the activities of west county irrigators are affecting Pendleton’s groundwater drinking water supply.

He pointed to a 2003 Oregon Water Resources Department study that stated limited connectivity between the city’s wells and west side irrigators, but said explicit knowledge of the connection is still unknown.

“Bottom line: we don’t know who’s connected to who,” he said.

As reported by The Oregonian, many aquifers like the Umatilla Basin suffer from a dearth of modern information, including the amount of water left in the aquifer and its recharge rate.

NOWA is a nonprofit that advocates diverting water from the Columbia River to Eastern Oregon farmers, establishing surface water as an agricultural “checking account” while using groundwater as a “savings account.”

If NOWA is able to convince the state to approve of its program, Cook said it would take the stress off the aquifer and allow for a more comprehensive study of the area’s groundwater.

“Who cares who points the finger at whom,” he said. “We’ve got a problem.”

Cook said it would be difficult to make ASR a financially viable option for westside farmers.

While cities can pass the costs of installing an ASR system to their ratepayers, west county farmers can’t raise the price of the carrots, onions or potatoes they sell and expect to compete in a global marketplace.

Cook said these kinds of products and all the associated industries they’ve benefited are the reason places like Hermiston and the Port of Morrow are experiencing rapid economic growth. With farmers already on board, Cook said more support from cities for NOWA’s cause would be mutually beneficial.

The future

If the trend isn’t reversed and water levels continue to decline, Patterson hopes a complete depletion of Pendleton groundwater wouldn’t happen for generations.

If the aquifer goes dry, Patterson said the city would have to rely entirely on the Umatilla River for its drinking water. Instead of drawing the surface water and banking it in below-ground storage areas, it would be transported to above ground containers for immediate use.

Besides the tens of millions of dollars such a system would require in new infrastructure, Patterson said Pendleton would lose water through evaporation at the compound and have to renegotiate water rights with the Confederated Tribes of the Umatilla Indian Reservation.

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Contact Antonio Sierra at asierra@eastoregonian.com or 541-966-0836.



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