NASA Data Feeds River Forecasts as Snow Drought Effects Linger
NASA satellite data is powering river-flow forecasts for Washington state’s Cowlitz River, helping Tacoma Power manage hydropower amid a lingering snow drought and extreme weather swings.
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NASA’s Earth observation data is being integrated into river-flow forecasts by Upstream Tech’s HydroForecast, which Tacoma Power uses to operate its Cowlitz River hydroelectric project. The utility relies on forecasts updated every two hours to guide reservoir releases, prepare for storms, and navigate dry periods, particularly during a 2026 snow drought that reduced mountain snowpack to 20%–50% of normal levels. The forecasts combine NASA satellite data on snow cover and vegetation with weather and river measurements to predict water availability from hours to days ahead, supporting decisions on water, power, and public safety.
The 2025–26 winter brought unusual warmth and below-normal precipitation to much of the western U.S., with January through March recording the lowest Western snow cover in NASA’s MODIS satellite record since 2001. On the Cowlitz River, this led to extreme conditions: a December atmospheric river caused one of the largest one-day inflow surges ever recorded, while spring runoff was among the lowest on record. By April, Washington declared a drought emergency for all watersheds, including the Cowlitz, leaving Tacoma Power with reduced incoming water to replenish reservoirs ahead of summer demand.
NASA’s VIIRS instrument on the Suomi-NPP satellite provides snow cover and vegetation data used by Upstream Tech to train HydroForecast models. The models analyze years of NASA data alongside weather forecasts and river measurements to identify patterns in water movement across hundreds of watersheds. Including NASA’s snow and vegetation observations improved forecast accuracy, according to Dr. Laura Read of Upstream Tech, who emphasized the need for reliable, globally consistent inputs for operational forecasts running every two hours.
Tacoma Power used HydroForecast to balance competing demands during the 2026 snow drought, keeping reservoirs higher than usual in spring to preserve water for summer while remaining prepared for potential storms. The utility entered summer with reservoir levels near average, supporting hydropower, fish habitat, and recreation. NASA’s data is also used by other agencies, including the USDA, NOAA, and the Bureau of Reclamation, to inform water-supply forecasts and reservoir operations across the western U.S.