Hydropowerproduction in the northwestern U.S. was above average in March and increased bynearly a third versus the prior monthto bring year-to-date figures above historical averages. But year-to-date totalsare below year-ago levels, implying a healthier water year for the region.
The data show that total net generation at 23 hydroelectric plantsacross the Pacific Northwest was 0.8% above the year-ago level and 19.7% above the12-year average as it reached 7.86 million MWh. That figure is up 1.82 million MWhfrom February.
The year-to-date data reflect a stronger build in snowpack aswarmer temperatures drove higher hydropower output in early 2015. Hydropower productionthrough March totaled 19.9 million MWh, down 15.8% versus the year-ago level butup 6.8% from the 12-year average for the period.
In the upper Columbia River Basin, the Grand Coulee Dam, thelargest of the region, generated 1.76 million MWh, down 18.6% versus the year-agomonth but up 10.1% versus the 12-year average for the period. The Chief Joseph Damgenerated 1.04 million MWh, down 14.7% versus March 2015 and up 16.6% versus the12-year average for the month.
Meanwhile, February flows in the lower Columbia River Basin werehigher versus historical averages. Located on the Washington-Oregon border, theBonneville Dam produced 613,477 MWh, up 2.5% versus March 2015 and 18.7% higherversus the 12-year average for the month. The Dalles Dam, 50 miles downstream, produced860,311 MWh, up 4.5% from the year-ago month and up 21% from the 12-year averagefor March.
According to data from the U.S. Department of Agriculture's NaturalResource Conservation Service, Lower Columbia River basin snowpack on April 7 was100% of the median, compared to a year-ago level of 11% of the median. Upper andlower Yakima River basin snowpack was at 76% and 118% of the median, respectively,compared to year-ago levels of 13% and 27% of the median. Snowpack feeding the SnakeRiver basin was 101% of the median, compared to the year-ago level of 58% of themedian.
During an April 7 presentation on the region's water supply,Northwest River Forecast Center senior hydrologist Kevin Berghoff noted that thistime of year marks the peak of the region's snowpack accumulation period, with thepeak stretching into late April or early May at higher elevations.
For April to September, the U.S. National Oceanic and AtmosphericAdministration predicts near-normal runoff conditions across the Columbia Riverbasin and coastal drainages. Forecasts issued April 5 for the upper Columbia Riverbasin project that water supply will be 102% of normal at the Grand Coulee Dam whileat the Lower Granite Dam, water supply will be 101% of normal.
Improved year-over-yearsnowpack in California does not alleviate drought concerns
Like the Pacific Northwest, California's mountains saw a muchhealthier snowpack compared to last year, but state officials still worry aboutthe historic drought faced by the Golden State.
According to the California Department of Water Resources, statewidesnowpack usually reaches its peak depth and water content around April 1 each year.As of March 30, statewide water content of mountain snowpack was 87% of the historicalaverage.
"While for many parts of the state there will be both significantgains in both reservoir storage and stream flow, the effects of the previous dryyears will remain for now," chief of the California Cooperative Snow SurveysProgram Frank Gehrke said.
According to the state agency, snowpack supplies 30% of California'swater needs in normal years as it melts and collects in reservoirs during the springand early summer.