To improve fish passage, water is spilled over the federal dams in the spring and summer to help juvenile salmon and steelhead migrate safely to the ocean. With this spill, most fish are guided to openings over or around the dam, rather than traveling through turbines. In addition to the traditional spillways, spillway weirs or other surface passage routes have been in place for nearly ten years at each of the eight dams on the lower Snake and Columbia Rivers. These structures allow juvenile salmon and steelhead to pass a dam near the water surface, similar to a waterfall, providing a more efficient and less stressful dam passage route. With the improved passage structures and implementation of the current spill program, fewer fish are passing through turbines or the turbine bypass screens than in previous decades. For adult fish returning from the ocean to spawn, fish ladders allow passage of upstream-migrating adult salmon and steelhead en route to their native spawning areas.
Fish operations, such as spilling water over dams rather than passing it through turbines, reduces the amount of water through the turbines and generates less electricity for BPA, and potentially reduces revenues. Less electricity generation can also result in the need for BPA to purchase additional power to meet energy needs.
These investments in current and future dam operations will continue. Each year, BPA directly funds the Corps and Reclamation for the portion of their costs to operate and maintain the fish passage improvements at the dams. An example of future improvements can be seen when turbines at the dams are ready for replacement. BPA and Corps have a program in place to ensure that new turbines are safer for fish while providing the opportunity for more efficient generation of electricity. The first examples of this new generation of turbines designed to increase the safety of fish passage are already in place at Ice Harbor Dam on the Snake River.