Editor’s note: The following report summarizes data from the WAPA Hydropower Conditions webpage for straight power purchase costs, which are based solely upon hydrology, actual hydropower generation and related generation shortages. Readers may review all data by visiting Hydropower Conditions

One of the biggest challenges for hydropower is water variability due to intermittent drought and flooding. By definition, hydropower needs water to generate electricity. Without it, WAPA must buy power on the open market from other sources to meet contractual obligations to its customers. This is referred to as purchased power.

In an ideal year, snowpack around the West is average or above average, yielding snowmelt runoff to recharge reservoirs behind the dams and powerplants that provide the power WAPA markets. Federal dam owners such as the Bureau of Reclamation, the Army Corps of Engineers and the International Boundary and Water Commission move water to federal hydroelectric powerplants.

WAPA markets the subsequent power generated to more than 700 preference customers. Its customers, in turn, sell that power to more than 40 million Americans.

Water around WAPA in 2018

WAPA’s actual generation was 107 percent of average in water year 2018, for a total generation of 27,308 gigawatt-hours. For the same period, total purchased power was 1,982 GWh with actual purchase power expenses of $53,834,864, which equates to $27.16 per megawatt-hour.

The Colorado River Storage Project Management Center projected most probable purchase power expenses for water year 2018 to be $18,490,664. Actual purchase power expenses were much lower, at $6,472,235. The cost per MWh was $25.87.

Lake Powell ended the water year with an elevation of 3,592 feet, which is about 96 feet above the minimum generation level and 108 feet below the maximum reservoir level. In water year 2019, dryness in the Upper Colorado River Basin may result in releases from Lake Powell being reduced from 9 million acre-feet to as low as 8.23 million acre-feet. If that were to occur, purchase power costs would increase by about $10 million.

Desert Southwest’s hydrology is mostly dependent on the Colorado River Basin snowpack and precipitation above Lake Powell. Precipitation was 65 percent of average at the end of September. The region’s most probable projected purchase power expenses were $12,818,219. Actual purchase power expenses were slightly higher at $13,779,771, with a cost per MWh of $62.15. Lake Mead ended the water year with an elevation of 1,078 feet, about 128 feet above the minimum generation level.

In Rocky Mountain, reservoir inflows were average or above average for the majority of the water year for all of the Loveland Area Projects. However, the July, August and September inflows were below average. At the end of September, inflows were only 47 percent of average. The projected purchase power expenses were $13,805,126, but actual purchase power expenses were significantly lower at $8,075,503. The cost per MWh was $24.11.

In Sierra Nevada, cumulative precipitation of the Northern Sierra Eight Station Index was at 81 percent of average at the end of September. Accumulated inflow for the water year was 45 percent of the 15-year average for Trinity, 100 percent for Shasta, 103 percent for Folsom, and 136 percent for New Melones. Reservoir storage as of the same date was 107 percent of the 15-year average for Trinity, 100 percent for Shasta, 103 percent for Folsom, and 136 percent for New Melones. The region began water year 2018 with a most probable projection of purchase power of $8,093,706 and ended notably higher at $12,155,514. The cost per MWh was $21.81.

In Upper Great Plains, runoff was above average at Gavins Point and below average in the Fort Peck, Fort Randall, Garrison and Oahe reaches. Portions of the upper Missouri River Basin continue to be impacted by drought. Abnormally dry and moderate drought conditions are present in much of North Dakota and northcentral and central South Dakota, with some areas experiencing severe drought. The water year ended with the active conservation pools for the Canyon Ferry and Yellowtail dams at 86.4 percent and 93.2 percent full, respectively. UGP’s most probable projection for purchase power was $11,306,473. Actual purchase power expenses were higher at $13,351,842. The cost per MWh was $21.62.

Anticipating the upcoming water year

The Seasonal Drought Outlook provided by the National Weather Service’s Climate Prediction Center in January 2019 predicted likely and persistent drought throughout the western United States. Notable drought conditions are not currently anticipated for the east. Drought removal or improvement is expected in Southern California, southern Arizona and some western regions of Oregon.

Exceptional drought, the NWS’ most extreme drought rating, is expected for central and eastern regions of Oregon, as well as the Four Corners region of Arizona, Colorado, New Mexico and Utah.

For more information, visit the National Weather Service’s Climate Prediction Center

Last modified on September 12th, 2023