A draft water supply forecast predicts that in the future, the Columbia Basin will have less water available in the summer and early fall. Problems could crop up with water availability by the mid-2040s, according to Washington’s Department of Ecology.
Every five years, the department must consider the long-term changes in water needs and supplies — and what that could mean for people and wildlife. By looking 20 years ahead in each report, water managers hope to help communities and lawmakers plan for long-term water needs.
“Infrastructure has aged, climate has changed, crops are diversifying, populations are moving, so the timing and quantity of our water supplies and demands are shifting,” said Melissa Downes, projects section manager for Ecology’s Office of Columbia River.
The department hosted a virtual public comment workshop on Tuesday.
People also can read and comment on the 2026 draft forecast online.
The draft forecast was put together by the Department of Ecology and the State of Washington Water Research Center at Washington State University.
The first report dates back to 2006. Most of the early forecasts focused on surface water, with an emphasis on agricultural demand, said Sasha McLarty, an assistant professor in WSU’s Civil and Environmental Engineering Department.
Starting in 2021, she said, the forecasting team delved more into municipal water needs. This year’s draft forecast also focuses more on groundwater, McLarty said.
The 2026 draft forecast looks at six topics, including vulnerabilities in water availability, groundwater supplies, water conservation and droughts lasting over two years. It also examines temporary worker housing and water demand, as well as how advances in climate change predictions could help water supply forecasts.
According to the draft report, as things get hotter, more rain will fall instead of snow — and what’s left of the snowpack will melt off faster. By the 2040s, that could mean less water supply in the summer and early fall.
Groundwater
For groundwater, the researchers wanted to know more about different pumping and aquifer recharge scenarios. Recharge is the amount of water going back into the groundwater system. Researchers were curious about how that could affect the amount of water in the future.
“Groundwater levels will continue to decline across most of Eastern Washington if we don't have any changes in recharge and pumping,” McLarty said.
However, there are ways to not deplete groundwater entirely.
Like the Odessa Groundwater Replacement Program, which aims to stabilize the area’s declining aquifer.
“Just by taking half of the users off groundwater within the (program) boundary, we see widespread increases in water levels simulated with this model,” McLarty said.
Conservation
This is the first year a water supply forecast has reported on conservation measures. The draft forecast looked at whether different conservation efforts actually saved water — and how it could affect entire watersheds.
“Changes in the timing and volume and location of water can shift,” said Julie Padowski, an associate professor in the School of the Environment at WSU.
The draft report found some conservation practices — like lining canals — can unintentionally affect other water users, she said. The lining leaves more water in the canals for irrigators, but it reduces water that would have seeped downstream, whether for other farmers or fish.
However, in the Walla Walla Basin, water managers have tracked what’s happening with the water supply. They’ve been able to add it back into the aquifer system to replace the water that can no longer seep through the canal lining, Padowski said.
“When people start to coordinate and look at impacts of conservation and measure some of those impacts, you can start to offset some of those things,” she said.
More research is needed to understand the cumulative effects of water conservation strategies, Padowski said. That could help people know if the money and effort they put into conservation are the best ways to help with water supply and demand goals, she said.
Drought
The draft forecast also predicts multi-year droughts could get worse as the climate continues to change, especially in the lower elevations of the Columbia Basin and Eastern Washington. It considered droughts that lasted two consecutive years.
“ We found that there is increased drought risk in Eastern Washington when we looked at snow droughts as well as the precipitation and dryness-based droughts,” said Vikram Chandel, a postdoctoral research assistant at WSU.
This year, Ecology declared a statewide drought. For parts of Washington east of the Cascades, this is the fourth year of drought in a row.
“We are already experiencing the increased pressures that come from consecutive droughts,” Downes said in a news release.
The draft forecast looked into the future problems caused by these types of droughts, Chandel said.
After interviewing farmers, the researchers found severe drought years can often mean fewer crops will be planted in the fall. Spring planting can then be delayed. Sometimes farmers switch to a less profitable crop. Irrigated plants can have a lower yield.
On-farm ponds and more efficient irrigation systems can be expensive for already cash-strapped farmers, he said.
Read the audio transcript here.
