BONNEVILLE POWER ADMINISTRATION
Federal agencies spill record amount of water at dams

The 2020 spring spill operation, a critical time for migrating juvenile fish, is nearing its seasonal end on the Columbia and Snake rivers. For the second year in a row, river operators implemented the flexible spill agreement that seeks to better balance the needs of both salmon and hydropower.

Much like in 2019, the 2020 flexible spill operation spills more water over federal dams than ever before to help juvenile endangered fish travel to the ocean. Beginning in early April and ending in mid-June, water is spilled 24 hours a day at federal dams on the Columbia and Snake rivers. For 16 hours a day, spill is provided up to the level of the new state water quality waiver of 125% total dissolved gas. River operators then reduce spill for eight hours per day when power market prices benefit energy production. The reduced spill levels for hydropower were developed and tested to support safe passage for young salmon and steelhead.

"We are encouraged by the continued coordination and active participation in this effort," said Scott Armentrout, BPA's vice president of Environment, Fish and Wildlife. "Working together, the agencies, tribes and states are accomplishing many things for salmon and steelhead, both in these operations and through our long-standing and wide-ranging habitat and hatchery operations throughout the region."

This year's spill increase to the level of 125% total dissolved gas at many dams is up from the 120% TDG levels implemented in 2019. Some believe more spill will be even better for migrating juvenile fish. However, at times high spill can cause delays in the migration of adult salmon and steelhead as they attempt to move upstream. Scientists and dam operators are working together to adjust spill levels to keep delays of adult fish to a minimum.

How much water is actually spilled at 125% total dissolved gas? For the 2020 spring operations, when river conditions allow, the four dams on the lower Snake River are spilling approximately 80% to 90% of the water that flows downriver, depending on the facility. On the lower Columbia, river operators are spilling approximately 40% to 75% of the passing water, also depending on the dam. Because of the large amount of water spilled, the 2020 operation results in greater periods of time when Columbia River System dams are operating at their minimum generation levels. Maintaining at least minimum generation is required at all dams for grid stability. And this year, because of higher spill rates, the amount of time dams are spending at minimum generation has increased. It's also good to remember that achieving the full amount of spill means river flows have to be high enough to sustain both spill and minimum generation.

Spilling huge portions of the river for 16 hours a day means dams can't generate as much hydropower. That leads to costs that must be absorbed in existing BPA budgets or recovered from ratepayers. However, the flexible spill operation gives BPA the ability to decrease spill and generate more hydropower eight hours a day at times when energy is more valuable, which provides some mitigation for the cost of higher spill. The agreement between states, tribes, BPA and its federal partners is designed for the spill program to be no more expensive on average for ratepayers than operations ordered by the courts in 2018, approximately $40 million.

And, in addition to the increase in spill this year, the agreement decreases summer spill starting two weeks earlier than in years past, beginning in mid-August, after most fish have completed migration. That means power revenues lost in the spring could possibly be recouped.

"The last two weeks of August are usually hot and dry with lots of regional power demand and a volatile power market," says Peter Williams, BPA operations research analyst. "By agreeing to spill more water for fish in the spring, we can spill less in late summer, and there's usually high power demand with high prices that could make up for the revenues lost in the spring."

BPA Power Operations staff say this spring's flexible spill operations have gone well overall, but they say the operations can be complicated and tend to take more time and attention to implement then previous spill regimes, partly because flex spill is still new.

"It's incredible to see our staff and how dedicated these people are as they work to ensure we meet biological objectives and that BPA gets the value out of this agreement that it needs," said Kieran Connolly, vice president of Generation Asset Management. "Every spill season is different because the amount of runoff in the river is so variable. Financially, we won't know for sure how well we've succeeded, until after the summer spill season."