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March 12, 2014
Southwestern Operates for Drought at Texoma

Significantly lower inflow than normal into the Lake Texoma (Denison Dam) watershed has caused Southwestern Power Administration, a not-for-profit administration within the U.S. Department of Energy (Southwestern), to severely limit power generation at Denison to conserve water storage.

“From May 2012 through February 2014, Southwestern generated only about 20% of average, which works out to about 1.8 hours a day,” explains Fritha Ohlson, Civil Engineer in Southwestern’s Division of Resources and Rates. “In fact, 2013 was the lowest year for generation since the project went online in 1945.”

Dension Dam Historical Generation (1945-2013)

Southwestern markets power in accordance with water control plans developed by the U.S. Army Corps of Engineers (Corps) in accordance with public law and various approved plans and procedures specific to each project. At Denison, pursuant to Public Law 100-71, restrictions on power generation are set by lake levels as follows:

Between 617-612 feet
Normal generation.

Between 612-607 feet
Rapid response, short term peaking, defined as the equivalent of 6‐8 hours full power generation per day in high energy demand months and 4‐6 hours full power generation per day in lower energy demand months, except to meet electrical emergencies.

Between 607-590 feet
Critical power needs, defined as the equivalent of 4‐6 hours of full power generation per day, except to meet electrical emergencies.

Southwestern has participated in several meetings with the Corps and legislative representatives from Oklahoma and Texas to discuss drought-driven lower lake levels at Texoma in relation to hydropower operations.

It has been explained at these meetings that the perceived rapid lowering of the lake level may be the result of a series of events in addition to the ongoing drought and record low inflow. The mild summer of 2013 created less of a demand on energy, so Southwestern was able to keep more water in the lake. With the onset of fall, however, thermal power plants began to be taken offline for maintenance, and Denison was pushed into service to help with regional electrical demand. This trend continued into the colder than normal winter, and was further exacerbated by natural gas shortages and spikes in natural gas prices, which made hydropower even more valuable to the region.

Another culprit that contributes to low lake levels is evaporation. According to Ohlson, total evaporation at Lake Texoma in the past two years has been larger than the total release for generation and is responsible for over 50% of the pool loss during that time.

The Corps estimates that Lake Texoma loses about 6 feet of water in an average year to evaporation. “People don’t really think about it,” Ohlson says, “but evaporation plays a huge part in reducing the pool, and hot, dry summers like we experienced in 2011 and 2012 tend to cause more evaporation than usual.”

Denison is financially integrated within the rate base composed of 22 of Southwestern’s 24 projects, so all customers in Southwestern’s six-state marketing area of Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas share in the costs and benefits of the hydropower produced at Denison.

As for continued drought operations at Texoma, Southwestern plans to participate in an Interagency Drought Management Committee (IDMC) meeting with the Corps and other stakeholders and a public meeting hosted by the Lake Texoma Association. Both events are tentatively scheduled for early April 2014.

March 12, 2014 Press Release - Southwestern Operates for Drought at Texoma



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pao@swpa.gov

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