The Frying Pan as a tailwater.
A tail water is a body of water released from a dam. In this case the dam is Reudi reservoir.
There are different types of tailwaters from the trout fisherman's viewpoint. There are top spill or surface release dams where the water spills over a spillway into the river below. These dams can also be referred to as diversion dams where the function is to merely create a body of water which creates a head for diversion for irrigation purposes.
Surface spill dams provide the advantage of releasing surface water and the plankton which lives in the surface water into the river below. For instance, caddis which feed on the surface living plankton will thrive in the water below such a dam. On the other hand, where the surface of the water warms in the summer, the release of the warmer water may stress the fish population.
The other major type of dam is a bottom release dam where the water is released from the bottom of the dam wall. Bottom release dams provide a number of advantages particularly where the flow is regulated and it is a deep dam which has collected spring runoff.
First, the water released from the bottom in summer months is colder than the surface of the dam. This is beneficial to trout populations and in fact in the absence of the dam the summer heat may stress the fish population to the point where the population is small and not numerous.
Further more bottom spill dams release nutrients and bug life which inhabit the bottoms of reservoirs. In a suitable environment with a plethora of released bug life and nutrients like the Frying Pan, the fish are large and more numerous.
In addition, the regulation of the water flow permits control of the spring runoff resulting in greater re-vegetation of river banks where once the spring run-off scoured them and damaged or destroyed the vegetation. The increased vegetation provides additional habitat for the insects and bugs which create the food chain for the trout.
Another benefit is that the thermal dynamics of a deep dam result in warmer water going to the bottom of the dam in winter. As a result, in winter when warmer water is released from the dam, it will insulate the river against anchor ice and freezing provided there is sufficient water released which mitigates this phenomenon. One detriment resulting from the regulation of the water temperature is that some bugs which require a great variation in water temperature may not have the variation to trigger their growth cycle. This may account for the reduced number of some types of larger stoneflies which appear to require the higher variation in temperature. Again, however, as the water leaves the proximity of the outlet it will be prone to larger temperature fluctuations and so this factor diminishes There is a good discussion of this in Ed Engles – "Fly fishing the Tailwaters".
Consequently, Ruedi being a bottom release dam, together with a rich nutrient source and careful management by the DOW has resulted in an exceptional fishery in the Frying Pan and the Roaring Fork rivers.
The intake for the outflow of the dam begins about 10ft from the bottom of the dam and the intake section is 62ft high. The following photgraph was taken in 1968 at the completion of the construction. It was kindly provided to us by Tim Beck of Zancanella and Associates who also provided us with the relevant technical details. Tim advises that the grids are trashracks.
Most of the water released into the Frying Pan passes through a turbine. The maximum release through the turbine can be 300 cfs. Additional water can be released separately in the case of high spring run-off flows. The turbine is sponsored jointly by the City of Aspen and Pitkin County. It can generate 5mw.
Tim Advises that this type of turbine sucks in a large volume of air and mixes it with the water which is discharged. The high dissolved oxygen content of the water is generally good for fish and other aquatic life. However, anglers should note that the highly air entrained water is not nearly as dense as water without the additional air mixed in. Therefore, if you fall in, you will not float as you would in normal water, rather, you would sink like a rock. The sign posted on the fence says it is dangerous, but doesn't say why.
In addition, the tailrace at the powerhouse exit is about 15 to 20 feet deep. So enjoy the benefits Reudi and the Frying Pan has to offer, but take care.
The newer constructed dams which release water from several levels, permits greater variation in temperature where the water from different temperatures can be mixed. This is the ideal solution when well regulated, which permits the creation of an environment which is more amenable to larger range of bugs which respond to the range of water temperatures.