The city of Walla Walla depends on the Mill Creek Watershed for water, which is fed primarily by a series of springs within the watershed, according to Tom Krebs, supervisor for Walla Walla’s Water Treatment Plant.
If stream levels in Mill Creek get too low, Walla Walla pumps water from some of its seven wells to supplement the water from Mill Creek. Groundwater is a finite resource that can be slowly replenished when rainfall or melting snow seep through the ground, but Walla Walla has an aquifer storage and recovery program that allows the city to add water back to the deep basalt aquifer.
Two of those wells are considered to be “recharge and production” wells, Krebs said, which means those two wells are used to recharge the aquifers. When there’s plenty of water in Mill Creek, the city draws from it, treats the water to meet drinking water standards, and pumps it back down into the basalt aquifer.
The program has allowed the decline of Walla Walla’s groundwater to slow. For example, one year Walla Walla pumped out 480 million gallons of water, Krebs said, but recharged it with 900 million gallons that year.
“I think we’re seeing the groundwater tables coming up, at least in the seven wells that we have,” Krebs said. “I know that in other places, the groundwater tables are dropping, and they’re not too far away from us.”
Most of the time, Walla Walla is putting more water into the aquifer than it’s taking out, and part of the reason for that is because water use in the Walla Walla Valley has changed over the decades, Krebs said, such as reducing irrigation for row crops. Losing the cannery and frozen food plant also reduced water usage, since they used 4-5 million gallons of water daily.
“Decades ago, in the ‘60s and ‘70s, the decline of the aquifer was 3 or 4 feet a year, and our recharge program has turned that around, at least in the city’s wells,” Krebs said.
Water use in Walla Walla has gone down over the past decade, but the recent heat wave and the drought raised water usage.
“When we start hitting 105-degree, 115-degree weather, people are doubling up on irrigation and trying to keep their grasses green and, you know, it puts a little bit of strain on the system,” Krebs said.
Krebs has worked as a plant supervisor for 32 years, and excluding the cannery’s water usage, Walla Walla’s water flows this year have been higher here, just for usage, than they have been in a decade or two, he said.
The city of College Place does not have access to surface water like Mill Creek, so unlike Walla Walla, it solely relies on the aquifer for water, and is unable to “recharge” its aquifer since it does not have the surface water to do so.
There are no serious plans for water restrictions in College Place, public works director Paul Hartwig said. Although the city recommends that people use their water wisely.
“Right now, we’re at a point where our pumps are set low enough that we don’t feel we’re in danger, unless unforeseen things happen like one of our well pumps or motors blows up, then we’d be in an emergency situation,” Hartwig said. “We always encourage people to use water wisely. Don’t waste it.”
If an emergency were to occur, College Place has many intertie agreements with neighboring systems, including Walla Walla, Hartwig said, so if College Place was in a situation where they had an emergency measure, they would contact the city of Walla Walla and initiate the agreement, although that’s dependent on if Walla Walla not having its own emergency.
Right now, the city is not in any danger, Hartwig said, and they will monitor what happens in the future, such as if there are good snow packs that will help the aquifer recover water.
Milton-Freewater also uses water from the basalt aquifer, although historically, it relied on the Walla Walla River for drinking water until the 1960s, when the water treatment plant was going to close and the city decided to fully switch to groundwater, said Steve Patten, Milton-Freewater public works technician.
The basalt aquifer doesn’t respond to drought conditions as fast as the shallower alluvial aquifer, so the impact on water levels in the surrounding wells may take a few years to see, Patten said.
“I think the biggest impact for the basalt system that the city uses is other users who may, because of the drought, not have enough water,” Patten said. “Some of them have basalt wells that are called supplemental water rights that they can then use if there are other water rights that don’t meet their water demands, and so my guess is that this drought is going to cause additional usage from the basalt aquifer system.”
Even before the drought, Patten said that the basalt aquifer on the Oregon side of the basin has been dropping anywhere from one to four feet per year in their area, which could mean that there is a larger increase in annual decline of groundwater.
“It also means that as water levels decline, it’s harder to pump water out, so you have to use more energy and get less water out of the ground as those water levels decline,” Patten said.
In a basalt system, there are natural “recharge zones” in the mountains that are fed by snow and rain, which slowly replenish the aquifer, Patten said. Milton-Freewater is also looking at implementing an ASR program of their own using the Walla Walla River.
“Starting about four or five years ago, the city of Milton-Freewater started doing feasibility studies and design work on one of the wells to look at the possibility of implementing an aquifer storage and recovery program here,” Patten said. “We’ve gone through the feasibility study, and it looks good. We’ve designed a system to treat water and then inject it into the ground, but we’re now in the process of trying to find some funding to help implement that.”
The big difference between surface water and groundwater is that while surface water renews itself every year through new rainfall and snow, groundwater is ancient water that can be thousands of years old that has been stored up over a long period of time that we’re slowly drawing down, Patten said, which is why we need to make sure that we don’t draw down too fast on it and run out of water.
More information about using and conserving water during the drought is available on the Washington State Department of Ecology website.