Anchor Reservoir is about as full as it can get

Many folks still like to joke that Anchor Dam does not hold water. But here is a photo, taken June 6, 2017, that is proof it does. In fact, Anchor Reservoir is as full as it can get. Completed around 1960 water seeped into sink holes, making the dam essentially unusable for storage. By 1970 a system of dykes was built behind the dam to prevent water from entering the more porous areas.

Today the reservoir will not hold what was once intended, but it does serve perfectly for flood control and also holds enough water to provide an additional late season water for irrigators between the dam and the Bighorn River.

On May 29, flows into Anchor from the South Fork of Owl Creek were roughly 100cfs. On June 5th just before midnight the flow into Anchor was 840cfs. Melting cycles make the peaks around midnight and the low flows (480cfs) come in shortly after noon each day. These are referred to as Diurnal Flow Cycles reflecting high daytime temperature runoff and slower runoff from the mountains at night.

At about an elevation of 6412' above sea level the water in the lake begins to run over a notch in the dyke and into an area where the sinkholes exist and it eventually disappears.

In a normal year this overflow would not be allowed to happen because it is simply a waste of water. But 2017 has not been a normal year and the water continues to pour down from peaks 9000-12,000 feet in the far west end of the county.

Oh, and then there is also North Fork of Owl Creek. The diurnals there peak about 350cfs. They flow unhindered and join South fork about two miles below Anchor Dam.

So, in an effort to prevent a total flow so high it would damage irrigator head gates down- stream, the excess water in Anchor is being allowed to go over the dike and be lost to the sink holes.

When all is said and done, Anchor Dam and Reservoir do a great job. Perhaps not as was originally intended, but in a Spring like 2017, residents downstream might be dealing with late night flows in Owl Creek of 1000-2000cfs. That would be a bad thing. Thank you Anchor Dam.