Hydroelectric power provider Tacoma Power in Washington state used satellite data from NASA to manage water reservoirs during severe weather swings across the Cowlitz River basin. The utility relied on real-time streamflow predictions from the artificial intelligence platform HydroForecast to adjust operations after winter snowpack fell to historic lows.
Developed by technology company Upstream Tech, the forecasting system combines meteorology and ground observations with satellite measurements of snow cover and vegetation. The artificial intelligence model updates every two hours to calculate water inflow into the river over periods ranging from several hours to several days.
Tacoma Power applied the predictions to prepare for storms, plan water releases, and store water to meet summer electricity demand. The company's largest hydroelectric complex on the Cowlitz River, linked to the Mayfield Dam and Mossyrock Dam, generates electricity for more than 151,000 homes each year.
Tacoma Power is a public electric utility that serves customers in Pierce County and surrounding parts of western Washington. The Cowlitz River originates in the Cascade Range near Mount Rainier and flows southwest into the Columbia River, making its watershed a vital source of renewable power and regional freshwater.
Extreme winter weather and record low snowpack
During the 2025-2026 winter, extreme heat caused much of the precipitation across the western United States to fall as rain rather than snow. Data from NASA's Moderate Resolution Imaging Spectroradiometer, known as MODIS, showed that January, February, and March recorded the lowest snow cover levels for those months since satellite observations began in 2001.
Across the Cowlitz River catchment area, snowpack remained at only 20 to 50 percent of normal levels.
In December, an atmospheric river brought intense precipitation to the region from the Pacific Ocean. This narrow band of dense water vapor triggered one of the largest single-day spikes in water inflow recorded since the forecasting project began. Because the heavy rainfall washed quickly downstream instead of accumulating as mountain snow, it failed to build the traditional winter snowpack that gradually melts to feed rivers throughout the summer months.
Spring drought emergency and reservoir management
When precipitation ceased in the spring, river inflow dropped precipitously. Washington state authorities declared a drought emergency on April 8 across all river basins in the state, including the Cowlitz River watershed. From April to June, maximum daily water inflow to the hydroelectric complex was among the lowest on record.
Short-term forecasts during the December flood enabled plant operators to estimate incoming water volume and prepare for sudden changes in river flow. When seasonal models signaled a risk of weak runoff in the spring, Tacoma Power kept its reservoirs fuller to retain water for the warmer months.
Maintaining higher water levels reduced the available storage capacity for potential new floods. To manage that risk, operators relied on two-hour forecasting updates to rapidly adjust dam operations whenever another atmospheric moisture flow approached.
Satellite data integration and summer outcomes
Upstream Tech trained the HydroForecast system by archiving years of NASA satellite observations, weather forecasts, and actual streamflow measurements across hundreds of watersheds. Information on snow cover and vegetation is gathered by the Visible Infrared Imaging Radiometer Suite, known as VIIRS, aboard the Suomi NPP satellite. This space-based instrumentation provides coverage across entire watersheds, including remote terrain where ground-based weather stations are sparse.
The Suomi NPP satellite is a joint Earth-observing mission operated by NASA and the National Oceanic and Atmospheric Administration. Incorporating satellite observations allows environmental monitoring systems to evaluate remote alpine regions that traditional rain gauges cannot reach, improving predictive accuracy in mountainous river basins. Tests across different basins demonstrated that adding satellite data increases forecast accuracy.
Despite the dry spring conditions, Tacoma Power entered the summer of 2026 with reservoir storage holding near average levels. The stored water supports ongoing electricity generation, maintains required river flow for fish and aquatic ecosystems, enables public recreation, and provides a backup reserve for potential heatwaves or emergency power outages.
NASA also provides its satellite data to federal agencies across the United States. The space agency shares satellite observations to assist with water supply forecasting, snowmelt calculations, and the publication of the weekly U.S. Drought Monitor.
