Authorization: Flood Control Act of 1965, approved 27 October 1965; Public Law 89-298, HD 232, 89th Congress, 1st Session.
Location: At river mile 114.7 on the Walnut River, a tributary of the Arkansas River, about 2 miles northeast of El Dorado in Butler County, Kansas.
Purpose: Flood control, fish and wildlife, water supply, water quality control, and recreation.
History of Construction: Construction began in October 1973, and the project was completed for full flood control operation in June 1981.
Type of Structure: The rolled earth-filled dam spans from STA. 1+90A, at the start of the Right Dike, to STA. 210+25A, at the end of the Left Dike, and rises to a maximum height of about 99 feet above the streambed. The top of the dam varies on either side of the spillway. 1+90A on the Right Dike to the right bank of the spillway at STA. 169+47A, and the design top of the embankment is 1369.87 ft. From the left bank of the spillway at STA. 174+02A to end of the embankment at STA. 210+25A on the Left Dike, the top of the embankment is 1370.5 ft. At STA. 191+00, Blue Stem Road cuts through the dam, and the surveyed elevation of the road way is 1367.5 ft.
The outlet structure consists of two 5.5 foot wide by 15.75 foot high hydraulically operated wheel gates. The concrete conduit should not be operated at a capacity greater than 4,200 cubic feet per second (cfs) or 60% full, which coincidentally corresponds with the downstream channel capacity in El Dorado, KS. The spillway is located on the left abutment and is 350 feet in length with a crest elevation at 1353. It has a capacity of 30,600 cfs at the max pool of 1,363.4. Water supply is currently piped under the outlet works conduit from the twin wet wells through a 36” diameter pipe.
Hydrologic Data: The flood of record occurred in June 1979. The estimated peak discharge at the El Dorado dam site (which was under construction at the time) was 41,200 cfs and the volume was 52,400 acre-feet. The estimated average rainfall above the dam site was 7.5 inches. On May 26th, 2019 the pool of record elevation reached 1,348.92 with a peak inflow of 26,100 cfs. The total volume of inflow from April 28, 2019 to June 30, 2019 was 220,028 ac-ft.