July hydroelectric power production in the Pacific Northwest diminished sharply versus the prior month, amid dry weather, but was mixed versus historical levels.
According to the U.S. National Oceanic and Atmospheric Administration's Northwest River Forecast Center, the month's precipitation was at least 50% below normal across most of the region. In spite of the dry weather, season-to-date precipitation from Oct. 1, 2016, through July 31, 2017, remained above normal.
Data from the U.S. Army Corps of Engineers show that total net generation at 23 hydroelectric plants across the Pacific Northwest was 13.8% above the year-ago level but 11.5% lower than the 10-year average as it reached 6.06 million MWh. That figure is down 33.2% from June.
Year-to-date hydropower production through July totaled 55.67 million MWh, up 19.1% versus the year-ago level and 14.6% from the 10-year average for the period.
In the upper Columbia River Basin, the Grand Coulee Dam, the largest of the region, generated 2.12 million MWh, up 7.8% versus the year-ago month but down 13.1% versus the 10-year average for the period. The Chief Joseph Dam generated 1.12 million MWh, up 8.1% versus July 2016 but down 3.6% versus the 10-year average for the month.
July flows in the lower Columbia River Basin were also higher versus the year-ago period. Located on the Washington-Oregon border, the Bonneville Dam produced 246,659 MWh, up 51.7% versus July 2016 but 14.8% lower versus the 10-year average for the month. The Dalles Dam, 50 miles downstream, produced 439,008 MWh, up 19.4% from the year-ago month but down 11.6% from the 10-year average for July.