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Chinook salmon spawning in Idaho’s Snake River.
IN D EP TH
CONSERVATION
Meager snows spell trouble ahead for salmon Without snowmelt, streams in the western U.S. could reach lethal temperatures
A
268
totals in the Pacific Northwest shows mostly light and dark red dots, indicating snow levels 50% of normal and below. A smattering of white dots indicates no measured snow at all. California’s Sierra Nevada is in even worse shape, as those mountains now hold only 5% of their normal snowpack. The state’s reservoirs are also only about half full. Faced with this combination, earlier this month California Governor Jerry Brown mandated an across-the-board 25% cutback in water deliveries to urban water users. Ironically, river and stream flows are still robust, at least outside California. According
sciencemag.org SCIENCE
17 APRIL 2015 • VOL 348 ISSUE 6232
Published by AAAS
CREDITS: (PHOTO) © NATALIE FOBES/CORBIS; (MAPS) ADAPTED FROM NOAA
to interactive stream flow maps maintained by the National Oceanic and Atmospheric lthough record snowfall in the northAdministration (NOAA), water levels in riveastern United States grabbed the ers that are prime salmon habitat across the headlines this winter, the mountains Pacific Northwest are surging. The maps are throughout much of the western peppered with pale blue and deep blue dots, United States remained unusually indicating flow levels 125% to 175% of norbare. Early to mid-April in the West mal. But that’s because for most of the wintypically marks the high point of the snowter, temperatures across the region were 3°C pack, which serves as a critically important to 6°C above normal, says Kevin Berghoff, a water bank that doles out reserves as the senior hydrologist with NOAA’s Northwest snow melts over the dry summer months. River Forecast Center (NRFC) in Portland, But this year the bank is nearly empty, Oregon. As a result, most of the precipitaand drought-stricken farms and cities in tion in the Northwest fell as rain rather than California can expect little relief. And for snow, swelling spring runoff volumes. endangered salmon miFlows are likely to grations, a calamity is drop dramatically in looming. “It’s going to the summer, accordbe a Katrina for fish,” Mapping the threats to endangered stocks ing to NRFC. With says Dan Isaak, a fisher- Mild winter temperatures in the Pacific Northwest caused most precipitation to fall as rain the exception of a few ies scientist at the U.S. instead of snow. That has left a snowpack far below normal (left) and is expected to cause river basins in central low stream levels this summer (right). Forest Service’s Rocky and eastern WashingMountain Research Staton, Idaho, and British tion in Boise. Columbia, virtually all CANADA CANADA Snowpack Projected stream flow He and others prethe rivers in the Northdict that when salmon west are expected to swim up western rivers have flow levels far beto spawn this summer, low normal. their eggs and young When summertime UNITED UNITED UNITED will perish in shallow, heat sets in, water temSTATES STATES STATES warm water. That could peratures in those rivthreaten already meager ers are likely to spike. endangered stocks, parIn many inland streams ticularly in California’s in California’s Central Central Valley, which Valley, as well as central faced similar disastrous Oregon and Washingconditions last summer. ton, river temperatures
Chinook salmon spawning in Idaho’s Snake River.
IN D EP TH
CONSERVATION
Meager snows spell trouble ahead for salmon Without snowmelt, streams in the western U.S. could reach lethal temperatures
A
268
totals in the Pacific Northwest shows mostly light and dark red dots, indicating snow levels 50% of normal and below. A smattering of white dots indicates no measured snow at all. California’s Sierra Nevada is in even worse shape, as those mountains now hold only 5% of their normal snowpack. The state’s reservoirs are also only about half full. Faced with this combination, earlier this month California Governor Jerry Brown mandated an across-the-board 25% cutback in water deliveries to urban water users. Ironically, river and stream flows are still robust, at least outside California. According
sciencemag.org SCIENCE
17 APRIL 2015 • VOL 348 ISSUE 6232
Published by AAAS
CREDITS: (PHOTO) © NATALIE FOBES/CORBIS; (MAPS) ADAPTED FROM NOAA
to interactive stream flow maps maintained by the National Oceanic and Atmospheric lthough record snowfall in the northAdministration (NOAA), water levels in riveastern United States grabbed the ers that are prime salmon habitat across the headlines this winter, the mountains Pacific Northwest are surging. The maps are throughout much of the western peppered with pale blue and deep blue dots, United States remained unusually indicating flow levels 125% to 175% of norbare. Early to mid-April in the West mal. But that’s because for most of the wintypically marks the high point of the snowter, temperatures across the region were 3°C pack, which serves as a critically important to 6°C above normal, says Kevin Berghoff, a water bank that doles out reserves as the senior hydrologist with NOAA’s Northwest snow melts over the dry summer months. River Forecast Center (NRFC) in Portland, But this year the bank is nearly empty, Oregon. As a result, most of the precipitaand drought-stricken farms and cities in tion in the Northwest fell as rain rather than California can expect little relief. And for snow, swelling spring runoff volumes. endangered salmon miFlows are likely to grations, a calamity is drop dramatically in looming. “It’s going to the summer, accordbe a Katrina for fish,” Mapping the threats to endangered stocks ing to NRFC. With says Dan Isaak, a fisher- Mild winter temperatures in the Pacific Northwest caused most precipitation to fall as rain the exception of a few ies scientist at the U.S. instead of snow. That has left a snowpack far below normal (left) and is expected to cause river basins in central low stream levels this summer (right). Forest Service’s Rocky and eastern WashingMountain Research Staton, Idaho, and British tion in Boise. Columbia, virtually all CANADA CANADA Snowpack Projected stream flow He and others prethe rivers in the Northdict that when salmon west are expected to swim up western rivers have flow levels far beto spawn this summer, low normal. their eggs and young When summertime UNITED UNITED UNITED will perish in shallow, heat sets in, water temSTATES STATES STATES warm water. That could peratures in those rivthreaten already meager ers are likely to spike. endangered stocks, parIn many inland streams ticularly in California’s in California’s Central Central Valley, which Valley, as well as central faced similar disastrous Oregon and Washingconditions last summer. ton, river temperatures
