When Shawnee City Commissioners met Monday, they heard a presentation made by Chad Ashworth and Jerrod Smith of the United States Geological Survey (USGS), sharing the results of a Shawnee Reservoir Bathymetry and Capacity Study.

When Shawnee City Commissioners met Monday, they heard a presentation made by Chad Ashworth and Jerrod Smith of the United States Geological Survey (USGS), sharing the results of a Shawnee Reservoir Bathymetry and Capacity Study.

The USGS, in cooperation with the City, performed a detailed bathymetric survey of Shawnee Reservoir (Shawnee Twin Lakes) in the field from June 21–September 7.

“Their investigation does confirm the March 2012 multi-reservoir yield analysis performed by CDM Smith,” Utility Director Steve Nelms said.

Ashworth said the objective of the bathymetric survey were to develop a detailed bathymetric map of the reservoir and determine the relations between stage (elevation of the lake) and reservoir storage capacity and between stage and reservoir surface area.

“We published the survey data and developed a web-mapping application to be issued to the public,” he said.

Funding for the project came in three portions: $15,500 from the city; and two portions from USGS — one from state-appropriated cooperative funds, and one from a USGS initiative to develop a new program “which we were very excited about because this was the first definitive project done by the USGS in Oklahoma,” Ashworth said.

The final report has been published and is available to the public, he said. Data can be found at https://doi.org/10.3133/sim3374.

“We used a manned boat with an echo-sounder mounted on the side with a GPS above,” he said, “to collect data on location and water depths.”

A major finding of the project, he said, was the storage capacity of Shawnee Reservoir in detail was 22,096 acre-feet at the normal-pool stage of 1,069 feet and 33,220 acre-feet at the flood-pool stage of 1,075.0 feet.

The bathymetric map may serve as a baseline to which temporal changes in storage capacity can be compared, the USGS summary reads. The stage-storage relation may be used in the reporting of real-time Shawnee Reservoir storage capacity at U.S. Geological Survey station 07241600 to support water-resource management decisions by the City of Shawnee.

“This will probably better tell us 10 years from now where we're at compared to what you're showing us now,” Ward 2 Commissioner Ron Gillham Sr. said. “It'll give us from now on a very accurate idea of where we're going.”

Smith agreed. “Absolutely,” he said.

The city can go in later and survey again within the same specifications, Smith said.

“It's a benchmark,” Gillham said.

Smith said the storage table can be used to gauge where the city is at any given time.

Like during droughts, Gillham said.

About the lakes

Shawnee Reservoir (Shawnee Twin Lakes) is a man-made reservoir on South Deer Creek with a drainage area of 32.7 square miles (U.S. Geological Survey, 2016a) in Pottawatomie County. The reservoir consists of two lakes connected by an equilibrium channel. The southern lake (Shawnee City Lake No. 1) was impounded in 1935, and the northern lake (Shawnee City Lake No. 2) was impounded in 1960. Shawnee Reservoir serves as a municipal water supply, and water is transferred about nine miles by gravity to a water treatment plant. Secondary uses of the reservoir are for recreation, fish and wildlife habitat, and flood control.

You can reach Vicky O. Misa at (405) 214-3962.