Below-average precipitation brought August hydroelectric powerproduction in the Pacific Northwest below both year-ago levels and historical averagesas it slid versus the prior month.

Across the region, August 2015 and August 2016 saw precipitationthat was well below normal, with the largest year-over-year deficit occurring inthe Canadian Rockies, the Olympic Mountains and the Cascades. The Willamette andSnake River valleys also saw precipitation decline year over year.

Typically, the region sees hydroelectric output reach its nadirin September or October, the months that demark the respective end and beginningof a given water year. Data for August from the U.S. Army Corps of Engineers showthat total net generation at 23 hydroelectric plants across the Pacific Northwestwas 7.7% below the year-ago level and 14.8% lower than the 10-year average as itreached 4.51 million MWh. That figure is down 15.2% from July.

Year-to-date hydropower production through August totaled 51.26million MWh, up 3.2% versus the year-ago level but down 6.1% from the 10-year averagefor the period.

In the upper Columbia River Basin, the Grand Coulee Dam, the largest of the region, generated1.72 million MWh, down 13.2% versus the year-ago month and down 10.8% versus the10-year average for the period. The ChiefJoseph Dam generated 871,467 MWh, down 13.3% versus August 2015 anddown 14.1% versus the 10-year average for the month.

August flows in the lower Columbia River Basin were also lowerversus the year-ago period. Located on the Washington-Oregon border, the Dam produced 113,769MWh, down 5.5% versus August 2015 and 32.3% lower versus the 10-year average forthe month. The DallesDam, 50 miles downstream, produced 293,924 MWh, down 7.7% from the year-ago monthand down 15.9% from the 10-year average for August.