How does an earlier runoff impact fish population and health?

A picture named cutthroat

From the Summit County Voice (Bob Berwyn):

…peak runoff is coming as much as two to three weeks earlier than it did as recently as the 1970s — an astounding change in a short time, measured on the scale of Earth history.
The researchers also pinned the timing of snowmelt and runoff to changes in global and regional temperatures, as well as reduced snowfall during the study period. The published their findings in the Journal of Climate last week.

Water managers have already been scrambling to understand how the changes will affect operation of reservoirs and diversions for agricultural and municipal use, but the shift in timing could also have huge impacts on aquatic ecosystems in the southern Rockies and desert Southwest. At issue is the growing gap between spring runoff flows and monsoon rains later in the summer. Fish native to the mountain streams of the region already live in a narrow window of flows and temperatures. If spring streamflows drop earlier in the year, trout and other fish could be exposed to longer dry periods…

“I expect that it will even further limit the amount of habitat,” she said. Hedwall and her colleagues have had to undertake intensive management efforts to maintain populations of some aquatic species.
The changes could also result in fish spawning earlier. Biologists think that fish may be able to adapt to those changes, but the real issue is year-round habitat. With longer, drier summers, it’s likely that many young fish won’t have enough habitat to survive. Water stored in reservoirs could provide a buffer against shrinking aquatic habitat if it’s used for environmental purposes.

More instream flow coverage here.

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