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FORECAST-INFORMED RESERVOIR OPS
“If you look at the major weather events over the last century,
particularly here in Yuba County, nearly all of the recorded floods are
connected to these powerful atmospheric river storms,” explained
John James, an atmospheric scientist and water operations project
manager with Yuba Water Agency. “Conversely, we also now know
that atmospheric rivers provide up to half of the annual precipitation,
benefitting our water supply.”
Recognizing the central role that atmospheric rivers play in
both flood risk and water supply – two of Yuba Water’s core mission
areas – the agency is investing in new research and tools to better
understand, forecast and manage for these powerful storms.
Bridging Climate Science and
Water Operations
After the 1997 New Year’s Day floods devastated Northern
California, Yuba Water initiated several actions to reduce flood
risk for communities along the Yuba and Feather Rivers. This
included significant investments in levee improvements and real-time
coordination of reservoir operations at New Bullards Bar on
the Yuba and the California Department of Water Resource’s Lake
Oroville on the Feather.
This coordination, known as the Yuba-Feather Forecast-
Coordinated Operations Program (F-CO), has expanded and
improved monitoring and information-sharing among federal,
state and local agencies in the region. The program also created the
foundation for a more modern and sophisticated forecast program
called Forecast-Informed Reservoir Operations, or FIRO.
Led by the University of California at San Diego’s Scripps
Institution of Oceanography Center for Western Weather and Water
Extremes, with partners including Yuba Water, DWR, the U.S.
Army Corps of Engineers and the California Nevada River Forecast
Center, the Yuba-Feather FIRO partnership was formed on the heels
of a five-year drought followed by near-record rains in 2017.
“California already has a highly variable climate,” James
said. “Climate change predictions indicate that these periods of
extremes will oscillate back and forth and increase in magnitude
and frequency in the future. FIRO is a perfect tool to help us manage
and adapt to these changes.”
While Yuba Water is primarily interested in reducing flood
risk with FIRO, its water supply benefits are also promising. In
the nearby Russian River Basin, Sonoma Water recently reported
a 19 percent increase in water storage at Lake Mendocino during
water year 2020, more than 11,000 acre-feet, thanks to the early
implementation of FIRO. Considering water year 2020 was the
third driest year over a 127-year record and the recent declaration
of a drought emergency in Sonoma and Mendocino counties, the
savings are significant, James said.
Partners like DWR are also optimistic about the application of
FIRO and its role in regional water operations.
“Our continued work with Yuba Water and Scripps on
potential advances in forecasting and monitoring atmospheric
rivers, and the benefits to flood control and water supply that could
result, will help DWR be better informed when it comes to water
availability, reliability and management,” said John Leahigh, State
Water Project Water Operation executive manager and co-chair of
the Yuba-Feather FIRO steering committee guiding implementation
of the program.
When implemented together, F-CO and FIRO combine
water management operations during potential flood events with
improved atmospheric river forecasts. The goal is to substantially
reduce flood risk for the Yuba-Feather watersheds by creating more
storage in reservoirs ahead of big storms while also ensuring water
supply reliability when prolonged dry conditions are forecast.
Using $2 million in funding from Yuba Water and DWR, a Yu-ba-
Feather FIRO workgroup is in the early stages of implementing
FIRO in the region. The funding has also helped establish five new
atmospheric river monitoring stations that collect continuous mete-orological
data like air temperature, humidity, pressure, precipita-tion,
wind speed and direction and solar radiation. Two additional
monitoring sites have also been identified and are expected to go
online in 2021.
Several stations also collect soil moisture at six depths below
the ground surface, helping researchers pinpoint the boundary
between snow-covered and snow-free surfaces in the
watershed. Two stations also include vertically
pointing radar, which can observe the
altitude in the atmosphere where snow
and ice turn to rain. This is important
because compared to other watersheds
The main spillway and dam at Lake Oroville (below). Photo courtesy of DWR.
The spillway at New Bullards Bar Dam and Reservoir (bottom). Photo courtesy
of Yuba Water.
Carly Ellis (left) and Kerstin Paulsson (right),
both with the Center for Western Weather
and Water Extremes at Scripps, conduct
maintenance on an atmospheric river monitoring
station located at New Bullards Bar.