Thanks to the leadership of the Colorado River District, preservation of fishing opportunities at Elkhead Reservoir near Craig, Colorado and critical efforts in support of protecting endangered fish downstream from the reservoir were accomplished with the installation of a spillway barrier net.
The Elkhead Reservoir spillway barrier net is an important component of the Recovery Program plan directly benefiting the native fish species in the Yampa River, including the razorback sucker, Colorado pikeminnow, humpback chub and bonytail by increasing survival rates.
The fish barrier net arrives in a bundle
Located a short 9-mile drive northeast of Craig, Colorado, and straddling the Moffat and Routt County line is one of northwest Colorado’s premier flat-water recreational hot spots.
Elkhead Reservoir was originally constructed in 1974 by Colorado Parks and Wildlife and the Yampa Participants, a consortium of power providers, as an earthen-fill dam with a total capacity of 13,700 acre feet of water for industrial and recreational use. Elkhead Reservoir is an on-stream reservoir on Elkhead Creek a major tributary of the Yampa River.
The watershed upstream of Elkhead drains a 205-square mile basin with a mean annual volume of 75,000 AF and peak flows of up to 2,500 cubic feet per second. The State of Colorado Water Quality Control Division currently classifies Elkhead Reservoir for the following uses Aquatic Life Cold I, Recreation E, Water Supply and Agricultural.
Rainbow over Elkhead Reservoir
Former capacity: 13,800 acre-feet
Enlarged capacity: 25,550 acre-feet
Cost to enlarge: $31 million
Old dam elevation: 6,378 feet
New dam elevation: 6,403 feet
Elkhead Reservoir Enlargement Project
The original construction allocated 8,310 AF for cooling water for the Craig Station Power Plant and 5,390 AF for a recreational pool. Elkhead Reservoir has long been known by locals as a great sport fishery which has lead to one of its most difficult management issues.
In 1979 the National Dam Safety Program determined the spillway hydraulically inadequate to bypass the probable maximum flood (PMF). Between 1979 and 1990 several enlargement/hydraulic studies were conducted as Elkhead Reservoir was always a good candidate for enlargement and the original facilities needed updating.
Several years of assessment of the potential human demand and the actual need for flow augmentation for the endangered fish resulted in the 2006 enlargement to create more human supply and 5,000 acre-feet of storage for endangered fish flow management. Construction of the enlargement took two years and was completed in 2006 at a total project cost of $31 million dollars.
The enlargement required raising the height of the dam 25 feet raising the normal pool 20 feet creating 11,956 acre feet of new storage; new outlet works and tower with an outlet capacity of 550 cfs, and a new labyrinth weir and spillway capable of conveying discharges up to 25,000 cfs.
Uniquely, the Upper Colorado River Recovery Program invested $13.6 million, including $6.5 million from the State of Colorado Native Species Conservation Fund, in storage in Elkhead Reservoir to assist with flow management on the Yampa River. Unlike other Colorado River tributaries, the Yampa River has no federal or other large storage to reprogram for flow enhancement in the effort to recover these endangered fish.
The Recovery Program is designed to protect the Colorado pikeminnow, humpback chub, the boneytail and the razorback sucker in the Upper Colorado River Basin. The other 6,750 AF of the enlargement is allocated for future water needs in the Yampa River Basin and funded by $17.3 million from the Colorado River District, which is partially financed through a construction loan with the Colorado Water Conservation Board (CWCB). Two-thousand acre feet of this pool is currently leased to the Recovery Program for 20 years. The varied ownership and uses of water stored in Elkhead Reservoir creates some unique management issues, none more important than the competition between the resident sport fish within the reservoir and the endangered fish downstream.
A major component of the planning and design of the enlargement had to clearly address containment of the resident sport fish within Elkhead Reservoir. Resident sport fish in Elkhead consist primarily of warm-water species like northern pike and smallmouth bass; however, the DOW does stock rainbow trout as a put and take species. Competition from non-native species has adverse impacts on the recruitment and restoration of the endangered fish population. Pike and bass are known to prey on the endangered fish in the river.
The recreational resource value of sport fishing in the area was deemed a valuable asset to the public and needed to be maintained. In order to maintain these seemingly opposing management goals, a means of containment for nonnative species in the reservoir is included. The Elkhead fish separation project was born and an advisory committee formed to evaluate the most effective means to achieve fish separation.
In the end a combination of the labyrinth weir design and stainless steel fish screens on the outlet works were recommended. The fish screens are equipped with a self cleaning pneumatic blower system to help prevent debris from clogging the screens. The construction of the fish screens alone added $750, 000 in costs to the enlargement which was funded by the Recovery Program in addition to the purchase price of the storage. Nonnative sport fish are not the only management concerns at Elkhead Reservoir.
The project also benefited from a $1.5 million CWCB mitigation grant which was shared by the River District and the Recovery Program to meet the other mitigation requirements such as wetlands impacts.
Like most reservoirs in the state Elkhead Reservoir has instituted a boat inspection program to help prevent the spread of the invasive zebra and quagga mussels. An infestation of these mussels could prove problematic to the effectiveness of the fish screens and severely limit outflow capacity and raise operating costs for divers to scrape the screens.
Operating and maintaining reservoirs in today’s environmental climate requires cooperation and sometimes complex solutions in order to achieve management goals. In the world of reservoirs Elkhead may seem small in size but is large in management complexity. Next time you find yourself in northwest Colorado looking to do some boating or fishing be sure to visit Elkhead Reservoir.
In 1990 the City of Craig entered into a transfer agreement with the Colorado Parks and Wildlife and acquired the dam and reservoir. Currently after the 2006 enlargement, maintenance and operation is shared between the City of Craig and the Colorado River District, and the recreation facilities are managed by Colorado Parks and Wildlife.
For the latest information Elkhead Reservoir, contact River District Deputy Chief Engineer Ray Tenney at 970.945.8522, ext. 220, or email firstname.lastname@example.org.