The US Energy Information Administration (EIA) expect US hydropower generation will increase by 7.5% in 2025, but will remain 2.4% below the 10-year average, according to the company’s May Short-Term Energy Outlook (STEO).
Hydropower generation in 2024 fell to 241 billion kWh, the lowest since at least 2010. In 2025, the EIA expect generation will be 259.1 billion kWh. This amount of generation would represent 6% of the electricity generation in the country.
About half of the hydropower generating capacity in the country is in the western states of Washington, Oregon, and California, so the EIA closely monitor precipitation patterns in this region to inform its hydropower outlook.
Precipitation conditions have been mixed across the western US since October 2024. According to the WestWide Drought Tracker, more precipitation than normal has fallen in northern California, Oregon, and the eastern half of Washington state. Some areas in south-eastern Oregon received record precipitation between October 2024 and April 2025. In contrast, precipitation was below normal in parts of Washington, Montana, Idaho, and Southern California.
Accumulation from winter precipitation tends to peak by 1 April 2025. The snowpack accumulation at higher elevations serves as a natural reservoir that melts gradually as temperatures rise in the late spring and early summer, leading to increased water flow through dams.
The EIA expect hydropower generation in the Northwest and Rockies region to be 125.1 billion kWh, which is a 17% increase compared with 2024 and 4% less than the 10-year average. The company’s hydropower forecast is informed by the water supply outlook from the National Oceanic and Atmospheric Administration’s Northwest River Forecast Centre (NWRFC).
On 1 May 2025, NWRFC released its April – September water supply forecast for the Pacific Northwest, part of the larger Northwest and Rockies region as modelled in the STEO. The NWRFC forecasts the region will have a below-normal water supply compared with the past 30 years in the northern portion of the basin, which includes the Upper Columbia River Basin, and above to near-normal water supply in the southern portion, which includes the Snake River Basin. Water supply conditions at the Dalles Dam, located near the mouth of the Columbia River on the border between Washington and Oregon, reflect those of the upstream Columbia River system. The forecast at the Dalles Dam as of 1 May 2025 was 85% of normal for the same period.
The EIA forecast hydropower generation in California to be 28.5 BkWh in its May 2025 STEO, which is 6% less than 2024’s generation. This total would be 15% more than the 10-year average.
As of 1 April, reservoir levels in most major reservoirs in California were above the historical average for this time of year. The two largest reservoirs in the state, Shasta and Oroville, were at 113% and 121% of the historical average, respectively. According to the California Department of Water Resources, snowpack conditions as of 1 April 2025 were at 118% of normal for the Northern Sierra Nevada, 92% for Central Sierra, and 83% in Southern Sierra Nevada regions. Warmer-than-normal temperatures in April 2025 led to some early snowmelt across the state. As of the beginning of May 2025, snowpack conditions were at 81% of normal for the Northern Sierra Nevada, 73% for Central Sierra, and 53% for the Southern Sierra portion.
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