The Department of Natural Resources and Conservation (DNRC) will be replacing a gate stem within the northwest guard gate tower of Nilan Reservoir, located west of Augusta. The reservoir will be drawn down after the 2020 irrigation season to create a dry work environment in which to complete the repairs. No alternative plan was deemed economical or feasible for this scope of work. This draw down should be completed by Sept. 15, and repair work will begin immediately.
Repairs should take approximately two weeks but could take up to two months depending on the extent of damage and corrosion within the guard gate. During this time, a residual pool should remain near the eastern gate of the reservoir.
The residual pool in the reservoir may be 65-70 surface acres and 20-25 feet deep. This should allow some of the residing rainbow and brown trout to overwinter. Some population loss is expected but a proportion of the population is expected to survive. Refill of the reservoir will begin as soon as repairs are finished, and the reservoir is expected to refill to 75% full by next summer.
Montana Fish, Wildlife & Parks will stock Nilan Reservoir in spring 2021 with rainbow trout. No fishing regulations will be altered during this timeframe. The FWP Nilan Fishing Access Site will remain open and camping will be available. However, water recreation access will become more difficult and the boat ramp will become unusable as water levels descend.
If you have any questions about this drawdown and repair, please contact the DNRC’s Water Projects Bureau at 406-444-6646. For more information about the Nilan Reservoir fishery, contact FWP at 406-466-5621.