Sedimentation at Paonia Reservoir

Background

Paonia Dam and Reservoir are located 16 miles northeast of Paonia, Colorado, on Muddy Creek, upstream from its confluence with Anthracite Creek. The two creeks together form the North Fork of the Gunnison River. The dam is owned by Reclamation, and is operated and maintained by the Fire Mountain Canal and Reservoir Company (FMCRC) and the North Fork Water Conservancy District (NFWCD).

Paonia Reservoir provides irrigation water to approximately 15,300 acres of land, and has recreation and flood control benefits. When the construction of the project was completed in 1962 the reservoir had an active storage capacity of 18,150 acre-feet. Sediment from Muddy Creek flows into the reservoir and has reduced the storage capacity of Paonia Reservoir to 15,600 acre-feet.


Outlet Works Repairs and Maintenance

The intake structure of the Paonia Dam outlet works has sustained significant damage. The concrete bulkhead is cracking and there is a risk that pieces of concrete will fall into the intake structure. If that occurs, dam operations and downstream delivery of water will be compromised.

Reclamation, FMCRC, and NFWCD will be clearing sediment and debris from the outlet works and repairing the bulkhead of the intake structure. The structure must be repaired for the reservoir to be fully functional. Work at the dam will begin in September 2017 and be completed in November 2017, weather permitting.

photo: Paonia Intake Construction Photo, Title: Intake structure during construction in 1961
Intake structure during construction in 1961
Developing a Sedimentation Management Plan and Environmental Compliance

At the current sedimentation rate the reservoir would be completely filled with sediment in another 150 years, gradually reducing the available pool over time. Long before sediment levels reach the full pool elevation however, reservoir intakes and outlet works are affected, adversely impacting project operations.

In 2010, in an effort to reduce the accumulation of sediment in the reservoir, the reservoir was drawn down in the early spring in order to use high spring run-off flows to flush suspended sediment through the outlet works before closing the gates to refill the pool for irrigation season. This has reduced the rate at which sediment is building, but a long term sedimentation management plan needs to be developed to allow for the full range of reservoir operations and to maintain the current reservoir storage. Reclamation will be starting the environmental planning process to gather ideas and public input on sediment management alternatives for Paonia Reservoir.

Last Updated: 8/15/17