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Extreme runoff generation from atmospheric river driven snowmelt during the 2017 Oroville Dam spillways incident
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  • Brian Henn,
  • Keith Musselman,
  • Leanne Lestak,
  • Marty Ralph,
  • Noah P. Molotch
Brian Henn
Scripps Institution of Oceanography, UC San Diego

Corresponding Author:[email protected]

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Keith Musselman
Institute of Arctic and Alpine Research
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Leanne Lestak
University of Colorado Boulder
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Marty Ralph
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Noah P. Molotch
University of Colorado Boulder
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In Feb. 2017, a five-day sequence of atmospheric river storms in California, USA, resulted in extreme inflows to Lake Oroville, the state’s second-largest reservoir. Damage to the reservoir’s spillway infrastructure necessitated evacuation of 188,000 people; subsequent infrastructure repairs cost $1 billion. We assess the atmospheric conditions, snowmelt, and runoff against major historical events. The event generated exceptional runoff volumes (second-largest in a 30 year record) partially at odds with the event precipitation totals (ninth-largest). We explain the discrepancy with observed record melt of deep antecedent snowpack, heavy rainfall extending to unusually high elevations, and high water vapor transport during the atmospheric river storms. An analysis of distributed snow water equivalent indicates that snowmelt increased water available for runoff watershed-wide by 37% (25-52% at 90% confidence). The results highlight an acute flood risk to public safety and infrastructure projected to increase in severity in a warmer and more variable climate.
28 Jul 2020Published in Geophysical Research Letters volume 47 issue 14. 10.1029/2020GL088189