During the hottest days of summer in Prineville, when the city’s data centers have cranked up the air conditioning, water supplies in the area can become strained. That’s when the city’s high-tech aquifer storage recovery system — designed to save excess water in winter for use in summer — kicks into gear.

Now, the multimillion-dollar system is getting an upgrade and could double its capacity by the end of the year.

Social media giant Meta, which has data centers in Prineville, is paying for a second injection well to add to the city’s storage recovery system. The injection system is basically a well in reverse — instead of pumping water from the ground to the surface it “injects” water down into porous geological formations to be stored for later use. A second well “recovers” the injected well water.

Severe drought has impacted water supplies in the greater Prineville area in recent years — lowering streams, threatening fish and leaving farms short of water. The existence of several data centers owned by tech giants Apple and Meta puts pressure on local resources as both use vast amounts of water to cool the servers inside their facilities. That water has to come from somewhere, and the chosen location is an aquifer deep under the Prineville valley floor.

Read more: Declining aquifer levels raise alarm among hydrologists, officials

But getting the water out of the valley floor and storing it on higher ground for use in summer required some creative engineering. The first injection well, completed in 2019 with an $8.7 million grant from Apple, can push 150 million gallons of water underground each winter, said Casey Kaiser, public works director for Prineville.

How does it work?

The aquifer storage recovery system begins by pumping water from low-lying areas in winter when demand is lower and bringing it to higher ground where it can be stored and used in summer when demand is greater.

“That is the beauty of the (aquifer storage recovery) system because it allows the city to more efficiently and more sustainably use our water,” said Kaiser.

The water comes from an aquifer lying beneath the Prineville valley floor and the Crooked River. In the first stage of the process, 17 wells are used to pump the water from depths of 80 feet to 140 feet underground. The water is then moved to a treatment facility where it is filtered.

Due to the way water rights are structured, pulling water directly from the Crooked River is not permitted, according to Meta spokesperson Melanie Row. But water can be drawn from groundwater below the river.

From the filtration facility, a booster-pump system pushes the water uphill to the injection well near Prineville’s airport, where it’s “injected” back underground. The aquifer beneath the injection well is an ancient channel of the Crooked River — it’s isolated, confined and able to store vast quantities of water, said Kaiser.

300-million gallon capacity

Kaiser said the city is close to completing the well design, and the project is on pace for completion by the end of the year. It will have a similar capacity to the first well, bringing the total water injection capacity to 300 million gallons a year — enough water to fill around 600 Olympic-sized swimming pools.

“To put that into context, (300 million gallons) is almost half of the total annual water demand for the entire city of Prineville,” said Kaiser.

Projected costs for the second well are between $1 million and $3.2 million, said Meta spokesperson Stacey Yip. Project costs are still being determined as the bid hasn’t been finalized.

Benefits and potential pitfalls

The system is designed to help Prineville balance its annual water use and provides additional capacity to serve growth or industry that may come to the city, Kaiser said.

On peak demand days, the data centers in Prineville use about 10% of the water used in Prineville, said Kaiser. But peak use only occurs during around 10 of the hottest days of summer, he said.

“Most of the time the data centers use very little water,” said Kaiser. “It’s tiny little windows of time during the afternoon or hot part of the day. Their overall water demand is relatively low.”

Brian Barney, one of Crook County’s three commissioners, said the project is now time-tested and functions well for Prineville.

“The records show it has been successful,” said Barney. “I think the city is doing a good job of being stewards.”

But biologists urge the city to proceed with caution as tinkering with groundwater has the potential to impact springs and rivers.

“Studies have found that for many aquifers, the impacts of groundwater development will eventually reduce groundwater discharge to springs and streams, impacting surface water quality and quantity,” said Jerry George, a fish biologist with the Oregon Department of Fish and Wildlife.

“Areas of spring recharge are critically important for providing a source of year-round cold water for trout, salmon and whitefish,” he said.

Groundwater decline

Data from the Oregon Water Resources Department from observation wells located in the area where water is pulled up for the aquifer storage recovery system show declines of 1 to 2 feet per year from 2019 to 2022. But the department said the aquifer declines aren’t necessarily caused by wells pulling water for the injection system.

“The department is aware of the short-term drop in water levels,” said Joe Kemper, a hydrologist with the department. “However, those are single, annual measurements that are likely more indicative of the height of water in the river or how recently the wells were pumped on the day they were measured.

“We will continue to monitor the trend but, at present, the measurements are not indicative of long-term, year-on-year, persistent declines that have been noted in other parts of the Deschutes basin,” he said.

Bill Nashem, the watermaster for the Crooked River Basin, said drought is one of the prominent factors causing aquifer-level decline in the valley.

“When we are in a drought situation, not only are we not getting precipitation, we are also not releasing water out of the dam for flood control either so we are not significantly wetting the channel on a regular basis in springtime,” he said. “So there are double whammies going on there.”

Mitigation plans

A program is in place to protect Crooked River flows for fish and aquatic life in winter — the time of year when river levels could be affected by pumping from the shallow aquifer. This comes in the form of 5,100-acre-feet of surface water stored in Prineville Reservoir.

The U.S. Fish and Wildlife Service and National Marine Fisheries Service make final recommendations on how and when to release water from the city of Prineville’s groundwater mitigation account, according to the Oregon Department of Fish and Wildlife.

Nashem said the mitigation water that the city has in Prineville Reservoir exceeds the total volume that it’s allowed to pump.

“I am not concerned at all,” said Nashem when asked about the sustainability of the new water injection system.

“To get the limited license for aquifer storage and recharge project the city and all of that well water has to be fully mitigated for. And in fact they have been mitigating well over and above what they have been using.”

Meta’s data center in Prineville has cut its withdrawal of water from a peak of 445,000 cubic meters, or 117.5 million gallons, in 2020 down to 240,302 cubic meters, or 68.4 million gallons, in 2022, the most recent year data was available.