Authorization: Flood Control Act approved August 18, 1941; Public Law 77-228, Project Document HD 440, 76th Congress, 1st Session. Water supply authorization is also included in Public Law 85-500, Section 01(b).
Location: On the Verdigris River at river mile 271.5, about 4 miles southeast of Toronto in Woodson County, Kansas.
Purpose: Flood control, water supply, water quality, fish and wildlife, and recreation.
History of Construction: Construction started in November 1954 and diversion began January 16, 1959. Impoundment began on March 15, 1960, and the conservation pool was filled on March 21, 1960.
Type of Structure: The dam consists of a rolled impervious and random earth filled embankment with rock-protected slopes and a controlled, concrete spillway. The length of the dam including the spillway is 4,226.68 feet. The maximum height of the embankment above the streambed is 90 feet, elevation 946 feet.
Spillway: The spillway is a gate-controlled, concrete-gravity, ogee weir having a gross width of 376 feet and a net overflow width of 320 feet. Spillway discharges are controlled by eight 40- by 25-foot tainter gates. The structure is located near the right abutment of the dam. Spillway discharge at maximum pool (elevation 940.6) is 253,000 cubic feet per second (cfs). Bank-full capacity below the dam is 6,500 cfs.
Outlet Works: The outlet works consists of seven 5- by 6-foot 6-inch rectangular sluices that pass through the base of the spillway along the centerline of each pier. The sluices are controlled by hydraulically- operated slide gates. A 24-inch pipe controlled by a 24-inch butterfly valve for normal operation and a manually-operated gate for emergency operation passes through the weir for low flow releases. Capacity of the outlet works varies from 7,400 cfs at the top of the conservation pool to 10,100 cfs at the top of the flood control pool. A 12-inch pipe is also located through the structure for future water supply.
Hydrologic Data: The peak discharge, which occurred from June 29 to July 16, 1951 (pre-construction), amounted to 130,000 cfs with a corresponding volume of 518,450 acre-feet. The maximum flood volume, which occurred in May 2019, amounted to 635,295 acre-feet, which is equivalent to 16.3 inches or runoff from the drainage area above the dam site.