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The Kirwin Unit of the Pick-Sloan Missouri Basin Program is located along the North Fork of the Solomon River in the State of Kansas. The unit features include a multiple-purpose dam and reservoir and a canal, lateral, and drainage system used to serve 11,435 irrigable acres. In addition to the irrigation benefits provided by the unit, it protects the downstream area from floods, conserves and enhances fish and wildlife, and provides recreation opportunities.
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The principal features of the unit consist of Kirwin Dam and Reservoir; Kirwin Main, North, and South Canals, and a lateral system to distribute the water to the unit lands.
Kirwin Dam, on the North Fork of the Solomon River near Kirwin, Kansas, was completed in August 1955. The dam is a rolled earthfill structure, with a structural height of 169 feet and a crest length of 12,646 feet. About 9,537,000 cubic yards of earth and rock and 44,000 cubic yards of concrete were used in constructing the dam, spillway, and outlet works. The initial capacity of the reservoir was 314,550 acre-feet; 89,650 for irrigation, 215,115 for flood control, and the remainder for dead storage. A concrete spillway on the right abutment of the dam can discharge 96,000 cubic feet per second of water at the maximum water surface elevation 1,773 ft. Fifteen gated sluiceways, discharging through the bottom of the overflow section into the spillway chute, are used primarily to make controlled releases of floodwaters.
The outlet works through the dam acts as a canal and river outlet. Both releases are made from a stilling well located near the downstream side of the dam. The capacity of the canal outlet is 175 cubic feet per second, and the capacity of the river outlet is 100 cubic feet per second.
Kirwin Main Canal begins at the stilling well at the downstream face of the dam and extends 13.4 miles on the north side of the river, where it branches into the Kirwin North and Kirwin South Canals. The initial capacity of the main canal is 175 cubic feet per second. The Kirwin North Canal continues on the north side of the river 14.3 miles and has an initial capacity of 70 cubic feet per second. The Kirwin South Canal crosses the river in a siphon, extends along the south side of the river for 16.3 miles, and has an initial capacity of 60 cubic feet per second.
Laterals extend from all three canals to serve the project lands. These laterals consist of the Kirwin Main, Kirwin North, and Kirwin South, and total approximately 38 miles in length. In addition, there are 2.4 miles of drains.
Kirwin Dam and Reservoir are operated and maintained by the Bureau of Reclamation. Operation of the reservoir is coordinated with that of other reservoirs in the Kansas River Basin. Water in the flood control capacity is regulated in accordance with instructions furnished by the Corps of Engineers.
Operation and maintenance of the canals, laterals, and drains are the responsibility of the irrigation district.
The Bureau of Sport Fisheries and Wildlife administers the water surface and the larger portion of the Kirwin Reservoir lands as the Kirwin National Wildlife Refuge.
In 1879, the central branch of the Union Pacific Railroad was constructed through the valley of the North Fork of the Solomon River to Kirwin and the town became the center of activity during the early days of settlement. The settlers had aspirations for a prosperous and well-developed area. However, because of the frequent droughts that occurred over the years, these hopes were not realized and many of the early homesteads were abandoned. Prolonged droughts of the 1930`s and damaging floods focused attention on flood control needs and water conservation. As a result of the investigations by the Bureau of Reclamation and the need for irrigation in the area, Kirwin Irrigation District No. I was organized officially in August 1950.
Detailed plans for developing the water resources of the unit were initiated soon after construction was authorized by the Flood Control Act of December 1944.
After the disastrous Kansas River flood of July 1951, public demand for adequate flood control resulted in appropriations authorized by the Congress for that purpose in the Supplemental Appropriation Act of November 1951. The act directed the immediate construction of Kirwin Dam and Reservoir for flood control, but permitted further study before the irrigation aspects of the unit were begun.
The magnitude of the unprecedented flood of July 1951 demonstrated fully the necessity for further regulation and control of the water resources in the Kansas River Basin and required modification of previous plans for the dam, the most important change being that the capacity of the reservoir for flood control was more than doubled.
The unit was authorized by the Flood Control Act of December 22, 1944, Public Law 534.
Construction of Kirwin Dam started in March 1952 and was completed in August 1955. The Kirwin Main, North, and South Canals were completed in January 1958.
Lands of the unit are highly productive and the growing season is ample for field crops. A wide variety of crops can be grown in this area, but the principal crops are corn, grain sorghum, and alfalfa hay.
Kirwin National Wildlife Refuge (NWR), the first national wildlife refuge in Kansas, was established in 1954 as an overlay project on a Bureau of Reclamation irrigation and flood control reservoir. The bureau owns the land and controls reservoir water levels, while the refuge staff manages all other activities on the land and water. The reservoir is fed by the North Fork of the Solomon River and Bow Creek. Both are intermittent streams, which means they may dry up in periods of low precipitation. The refuge and reservoir are open 24 hours daily. The primary purpose of the Kirwin NWR is to provide nesting cover, food and shelter for song birds, waterfowl, upland game birds, and mammals. Wildlife oriented recreational activities such as fishing, hunting, wildlife observation, and photography can also be enjoyed at the refuge. Fishing for walleye, black crappie, largemouth and smallmouth bass, wipers, channel catfish and other species is permitted year round. Hunting for waterfowl and upland game is permitted during the appropriate season.
Kirwin NWR, located west of the town of Kirwin in Phillips County in north-central Kansas, was established to provide habitat for and facilitate the management of the Nation`s migratory bird resource. The topography of the refuge is rolling with grass covered hilltops nearly 200 feet higher than the wooded creek bottoms.
A reservoir, established primarily for flood control and irrigation, covers 5,079 surface acres at conservation pool level. Primary water source for the reservoir is Bow Creek and the north fork of the Solomon River. Due to fluctuating water levels the 5,079 acres are often divided between water, mud flats, and timber/brush growth.
The remainder of the refuge is composed of 1,600 acres of cropland, 3,749 acres of grassland, and 400 acres of riparian areas and shelter-belts surrounding Kirwin Reservoir. Kirwin Refuge serves as a migration stop over for waterfowl and as a staging point for water birds including Pelicans and Cormorants. Kirwin also has a large winter population of both Bald and Golden Eagles and a large population of other species of hawks and owls. The refuge provides important nesting cover, food, and shelter for songbirds.
With proper water levels the refuge provides exposed mud as feeding areas for spring and fall migrations of shorebirds. Kirwin Refuge also provides food and cover for resident populations of white tailed and mule deer, pheasant, bobwhite quail, greater prairie chicken, and the Rio Grande turkey.
Before construction of Kirwin Dam and Reservoir, numerous floods damaged or destroyed valley crops, livestock, and property and contributed to losses far downstream along the mainstem rivers. The flood control capacity provided in Kirwin Reservoir is large enough to completely control the largest flood of record and maintain the outflow at a safe channel capacity. As a result, most of the floodwaters can now be harnessed for beneficial use.
Kirwin Reservoir has an exclusive flood control capacity of 215,115 acre-feet and a surcharge capacity of 198,470 acre-feet for a total flood control capacity of 413,585 acre-feet. As of 1998, Kirwin Reservoir has prevented $75.4 million in flood damages.