Winter pulse flows benefit fall-run salmon fry by helping them emigrate to the Delta and Bay nursery areas (see discussion in February 2019 post). The tailwater spawning reaches of dams need reservoir releases to stimulate emigration of fry (Figure 1). Such releases piggy-back on stormwater flows in downstream tributaries, such as those in late January 2021 (Figure 2).
Nearly all Central Valley reservoirs are capturing recent high precipitation from their upper watersheds. With forecasts of further substantial rainfall into mid-February 2021, modest reservoir releases would provide substantial potential benefits to Central Valley salmon populations.