Study looks at water delivery in a post-dam Snake River

A study looking at ways to replace water delivery that would be disrupted if the four lower Snake River dams are breached includes elaborate solutions and high price tags.

But the document also says the Snake River with or without dams has more than enough water to meet current and future withdrawals for domestic, industrial and agricultural use.

According to the study, water supplied by the dams for crop irrigation and municipal and industrial uses indirectly supports about 6,400 jobs and $961 million in economic output.

While breaching the dams would not lessen the availability of the water in the river, it would require significant modifications or addition to the systems that divert the water to end users. Potential solutions include a storage reservoir on Hatwai Creek near the Clearwater River Casino, a diversion station just upstream of the Snake and Clearwater rivers, wells in the Little Goose and Lower Monumental dam pools, and pumping stations and pipelines near the Tri-Cities.

The report, authored jointly by the U.S. Bureau of Reclamation and the Washington Department of Ecology, is part of the settlement agreement between the U.S. government and the Nez Perce and other Columbia River tribes, the state of Oregon and environmental groups over lawsuit challenging the federal plan to balance dam operation on the Snake and Columbia rivers with the needs of threatened and endangered salmon and steelhead. It looks at how water from the lower Snake River is used and what would need to happen to sustain that use if the dams were breached.

The authors came up with four possible alternatives that mix and match various solutions and range in cost from $1.7 billion to $3.5 billion. They note that potential solutions are myriad and the four alternatives they crafted are far from the only ones available.

If the dams are breached, the surface of the Snake River would fall by 20 to 120 feet in elevation, with the biggest drops occurring just upstream from the dams. Breaching would result in lowering of the water table by about 12 feet within one mile of the river and 3 feet farther away. The report indicates that most wells would remain viable but some may need to be replaced. Most of those are near the Tri-Cities.

The proposed reservoir at Hatwai Creek would store 22,600 acre feet of water and be accompanied by a water pumping station on the Clearwater River and 45 miles of pipeline that would deliver water to Clearwater Paper, Lewiston, some water users in Clarkston and Asotin County and to irrigators as far downriver as Wawawai. The reservoir would be filled during high flows or at times when power prices are low. The pumping station would be able to fill the reservoir and supply water to the pipeline at the same time.

The reservoir is included in the most expensive alternative — $3.5 billion. The cheaper alternatives would rely on a $660 million water diversion and pump station near the confluence and 43 miles of pipeline to deliver water to the same users.

The highest use of water from the Snake River comes from irrigators who pump out of the Ice Harbor pool on the Snake River and the McNary Pool on the Columbia River. Here the Bureau of Reclamation proposes to construct pumping stations and pipelines to replace existing pump stations. The cost, depending on the configuration, ranges from $950 million to $2.1 billion.

The existing irrigation withdrawal system was privately constructed and the owners, represented by the Columbia-Snake River Irrigators Association, are critical of the study, don’t want the Bureau of Reclamation anywhere near their equipment and say if the dams are breached, they could alter the system for much cheaper.

The study concludes that about 52,000 acres of crops are irrigated by water withdrawn from the lower Snake River. But the irrigators association says it should be 92,000 acres. The irrigators also believe the study underestimates the degree to which sediment deposition and siltation will affect water withdrawal in the McNary Dam pool as far downstream as the mouth of the Walla Walla River and underestimates the value of irrigated land. Lastly, the irrigators believe work to adapt the withdrawal system if the dams are breached will lead to a one to two year disruption in irrigation.

But despite that, they think the study overestimates the cost of the work. Instead of building pumping stations and pipelines, Irrigation Association Board representative Darryl Olsen said the irrigators would prefer to adapt each existing station themselves.

“If society says we are going to full dam breach and Ice Harbor Dam is in that configuration, then what we are telling the feds and state and court is all you have to do is write us a check for $760 million and we will take care of it,” he said.

Lewiston Mayor Dan Johnson was also critical of the study. He said it didn’t account for Lewiston’s existing efforts to replace its water intake station on the Clearwater River and faulted the way it described the local economy.

“The price tag is huge and possibly underestimated,” he said.

Environmental groups said the study is promising.

“The biggest finding, that there is plenty of water, is really important,” said Michael Charles, communications director for the Columbia/Snake River Campaign.

He noted the region spends hundreds of millions of dollars each year in the effort to recover Snake River salmon and steelhead.

“Since the 1980s more than $24 billion has been spent on salmon recovery. This actually in the end could end up being a savings,” he said of the estimated cost.

The Columbia Riverkeeper commissioned a recent study that found that because the dams pool water and increase the surface area of the lower Snake River, they lead to 30,400 acre feet of evaporation annually, compared to evaporation on an undammed river.

“I think that is an important dimension of this conversation is not being quantified and not being talked about,” Miles Johnson, executive director of the conservation organization.

The U.S. Bureau of Reclamation and Washington Department of Ecology will hold a public meeting on the water replacement study from 4:30 to 6:30 p.m. Feb. 5 at the Lewiston City Library.

The study is available at bit.ly/40wkODz.

Barker may be contacted at ebarker@lmtribune.com.