Those of you who have enjoyed fishing on South Boulder Creek below Gross Reservoir (SBC) may have been surprised by rapidly changing water levels during the course of the day. This article explains how it works and what you can do about it.

HOW IT WORKS:

On SBC, Denver Water usually changes the level coming out of the dam at 9am, weekdays. They are "restricted" to flow rate changes of 50cfs/hour. This flow change rate can cause problems for fish and anglers. For example, if the flow is at 120cfs, and they lower it 100cfs, then the fish have only two hours to find safe locations. Imagine what this does to a spawner. If, on the other hand, the flow is at 100cfs and they raise it 100cfs, and you happen to be on the wrong side of the river between Ethel Herrod and Walker Ranch Loop Access, then you might have to spend the night. 

Additionally, if the water drops precipitously, the fishing will likely be bad until the fish settle into their new spots (day or two.) If it rises quickly, the fishing might be very good as such a rise usually scours food from the river bed, causing a feeding evetnt; good time for San Juan Worms, and Stonefly imitations. 

The decision to make these changes is complex; involving water storage balancing, inflow into Gross, weather, agriculture, and water system repairs. 

WHAT TO DO ABOUT IT:

I have brought this issue up with many members of Denver Water and Trout Unlimited. My main point was that surely they make the decision for these flow changes at least one day ahead of time. I had hoped that they could put a day-ahead warning of flow changes on their water flow website. (Click here, for hourly updates of the dam flow.) Denver Water declined to do that, but instead gave me a number that I could call and get current a forecast. The number is 303-628-6510. Call this number the day before you are planning to go and Cindy will usually answer. She is kind and informative. Call later in the day for the most up to date information. If enough people call enough times, maybe they will just put it on the website.

OTHER FLOW INFORMATION:

Trout Unlimited is working with Denver Water on getting minimum winter flows for SBC. This would be fantastic for SBC trout. On the downside, this could have a disastrous impact on the Fraser River. The odd thing is that recommended (Co DOW) minimum flow is 7cfs ... huh? Why not 10? A minimum flow of 15 would make this a premier fishery.

After years of study, I have concluded that fish like water.

Wallace