Pacific Northwest hydropower production in August had mixed comparisons against historical averages amid warmer-than-normal and drier-than-normal conditions.
Temperatures over most of the Northwest exceeded the norm by 1 degree to as much as 6 degrees F in August, while precipitation was largely 50% below normal, according to the U.S. National Oceanic and Atmospheric Administration.
Data from the U.S. Army Corps of Engineers show that total net generation at 23 hydroelectric plants across the Pacific Northwest was 7.9% higher than the year-ago level but 6.7% below the 10-year average as it reached 4.81 million MWh. That figure is down 19.3% from July.
Year-to-date hydropower production through August totaled 59.03 million MWh, down 1.8% versus the year-ago level but up 8.4% from the 10-year average for the period.
In the upper Columbia River Basin, the Grand Coulee Dam, the largest of the region, generated 1.76 million MWh, up 6.9% versus the year-ago month but down 6.7% versus the 10-year average for the period. The Chief Joseph Dam generated 950,635 MWh, up 6.6% versus August 2017 but down 4.2% versus the 10-year average for the month.
August 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 122,056 MWh, up 6.6% versus August 2017 but 24.7% lower versus the 10-year average for the month. The Dalles Dam, 50 miles downstream, produced 318,429 MWh, up 6.5% from the year-ago month but down 6.8% from the 10-year average for August.