The dams were built to allow barges to carry goods up and down the river to Lewiston, Idaho’s inland port, but they’re no longer needed for navigation. Freight traffic has declined for 20 years. At this point, this heavily subsidized transport can easily be replaced by existing (and less expensive) rail infrastructure right alongside the Lower Snake River.
Likewise, the dams are not necessary for irrigation. Only one dam, Ice Harbor, is used for incidental irrigation that can be replaced by extending pipes to the river, at less cost than preserving the dams. Meanwhile, breaching would expose 8,000 acres of fertile agricultural land–along with the 140 miles of Chinook spawning habitat.
Lastly, the LSRD do not provide flood control.
These dams have already cost a fortune in economic as well as ecological terms. Their anticipated expense to maintain far outweighs the cost of breaching. Just the turbines alone are coming to end of life and prohibitively expensive or impossible to replace.