Thursday, April 30, 2015

The Lake Is Back!

Honey  Grove Photo Club enjoys a tram tour along the marshes.
(Photo by Skip Hill)

American Avocet at HNWR
(Photo by Leslie Knudtson)
The lake is back! With recent spring rains, this week the lake level rose to nearly 617 ft. above sea level. In January, 2015 the lake level was between 611 and 612 feet above sea level. A little over a year ago, in March, 2014, the lake level was only 608 ft. 

The lake began filling in 1944 and soon attracted visitors for fishing, boating and swimming. According to information from the US Army Corps of Engineers, the lake elevation went to a low of 599.96  ft. in 1957. then, later that very same year, the lake experienced a record setting flood elevation that sent water over the spillway for the first time since the lake was constructed.

When you google Lake Texoma level you will see a reference to the conservation pool.  
From top to bottom, reservoirs typically have three “pools” – the flood pool, the conservation pool, and the inactive pool. The design elevations of the pools do not change although the lake level fluctuates depending on rain, evaporation, and water use. 
The conservation pool at Lake Texoma refers to the volume of water contained between
the top elevation of 617.0 ft above mean sea level (modified seasonally down to 615.0 and up to 619.0) and the bottom elevation of 590.0 ft. The volume of water in the conservation pool is considered to be set aside as “storage” to satisfy congressionally authorized project purposes such as water supply and hydropower.  The top of the conservation storage marks the bottom of the flood pool, which is used for temporary storage of excess water following heavy storms. The bottom of conservation storage marks the top of the inactive storage pool, the part of the reservoir designed for hydropower head and storing sediment, typically holding lower quality water due to its depth.

From Wikipedia, we learn that 
 "The lake has crested the dam's spillway at a height of 640 ft (195.07 m) three times: once in 1957, again in 1990, and most recently on July 7, 2007.[2] (USACE 2003a). The lake's highest elevation was recorded on May 6, 1990 at 644.76 feet.[3] The top of Denison Dam is at 670 feet. In May, 2009, Wildlife Drive and much of the Refuge was once again flooded when the lake levelreached 629 ft.
Lake Texoma's two main sources are the Red River from the west and Washita River from the north. Other notable sources include Big Mineral Creek, Little Mineral Creek, Buncombe Creek, Rock Creek, and Glasses Creek. Lake Texoma drains into the Red River at the Denison Dam."

Denison dam controls a drainage area of approximately 39,719 square miles.   According to the US Army Corps of Engineers, it takes significant rainfall across the entire watershed that feeds Lake Texoma to bring water levels up. "In general, a persistent exceptional drought for the last three years has gripped much of the Lake Texoma watershed. Evaporation of water is also a contributing factor. On an average year, Lake Texoma loses approximately six feet (74”) of water to evaporation. When the Lake Texoma basin does not get enough rain, the combination of evaporation and ongoing water usage will cause the lake level to drop."

Now, thanks to abundant rainfall, as Goldilocks declares in the "The Three Bears", Lake Texoma is “just right”. The ponds at Hagerman National Wildlife Refuge are full, there is water in Harris Creek and the marshes again, and Refuge staff have been able to put the two “Tern Islands”, aka artificial nesting platforms in place just in time for the Least Terns' arrival in mid-May.

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