Dillon Dam Project Update -December 23, 2014
A major maintenance project on The Dillon Dam, which began in August, continues as we close out the year. Originally scheduled to wrap up in the later part of December, delays have pushed it back slightly to the early part of January.
As we have mentioned in our previous reports, the river is not operating in a typical tailwater release at this time. Water continues to be siphoned from near the surface of the reservoir instead of being drawn from the bottom; as a result there are no Mysis Shrimp in the river at this time. That will change once the maintenance on the dam is complete and operations return to normal. According to Denver Water, that could be as early as January 5th but, could be delayed until the week of the 12th if inclement weather hampers the effort.
When the work is finished, it will be necessary to test the outflow works (the “tailwater” drawn from the bottom of the dam) to insure that everything is running properly. To do this, Denver Water will be running a mix of water through the siphon, as well as through the outflow works, which may take a day or two to complete. Once that is done, they will switch over to 100 percent bottom draw and remove the siphon apparatus.
At that point it will also be necessary for Denver Water to purge some excess storage that has accumulated over the past four months of restricted releases, approximately 5,000 acre feet. That will result in higher flows for the Blue River through Silverthorne. Although, we haven’t gotten a firm number on how many cubic feet per second that will translate to or for how long, we are guessing it will be close to 200 cfs for 2 to 4 weeks.
When that finally does happen, it should translate to a shrimp bonanza in town. Typically, an increase in releases from Dillon results in a flush of Mysis, particularly early on in that release. A release rate of 200 cfs should provide plenty of pull to bring good amounts of shrimp into the river, while allowing for a larger diameter of tippet to hang onto fish hooked in those slightly elevated flows. Those first 2 days may be a little hard to forecast what will happen, with the mix of the water column. It may or may not be enough “bottom” feed to draw large numbers of shrimp but, it might still be enough of a boost to put just enough shrimp in the river to kick things off.
In the interim, results have been good on a wider range of nymph options including Midge pupa, larva and emergers, small mayfly imitations such as RS-2, WD-40, Winter Baetis and Pheasant Tails along with a mix of egg patterns and San Juan Worms. Dry fly action continues to be good, but scattered. It has also been technical, with some angers dropping to 7x tippet and size 24-26 Midge adults. If you are serious about throwing dries, you can find fish feeding on the surface.
We will update the fishing report as things change and don’t hesitate to call us for any questions that you may have.