According to preliminary data from our Electricity Data Browser, the least hydropower was generated in the western United States during the 2022–23 water year (October 1 through September 30) since at least 2001. Western region hydropower generation dropped by 11% from the previous water year to 141.6 million megawatthours (MWh). Hydropower generation in the western United States can vary significantly from year to year because the amount of precipitation influences generation.