Tim,
That is a great question and I'm very glad you asked. You clearly explain a common concern I've been hearing from kayakers, but just was not fully understanding: the relationship between Bailey and Gore. I finally get it and I can shed a little light on this--although not enough to answer all of what you have asked. Still, here's my best shot:
Yes, the Roberts Tunnel diversion from Dillon to Bailey Canyon is based upon water demands in Denver. When demand is on, Denver Water will divert from Dillon through Roberts. When Denver does that it can impact how much water is being released from Dillon on down the Blue to Green Mountain, but not always.
As you explain, it does all have to do with water rights. Per the Blue River Decrees, Dillon can store Green Mountain water during run off (Green Mountain is the senior right) and then release that water to our customers from William's Fork (their reservoir) later on in the season. This is through a substituion or exchange.
During run off, Denver cannot store a full Dillon until Green Mountain is full--again, it's the senior water right. But, we do not have to fill physically. The Decrees allow for water accounting and that storage elsewhere as mentioned above. In years like this year when we have had a lot of snow in the Blue River basin, Denver was able to bypass inflow to us until we physically filled Green Mountain. No need for an exchange this year or an "on paper" fill at GM. After we filled GM, Denver about filled Dillon. Snow kept melting, so they kept bypassing the large inflows and we did likewise.
When run off started coming to an end, I believe Denver Water's operations change and they come in to priority to divert--I don't know this for sure and you would have to double check with them. At any rate, when demands got high in Denver or their right came on, they started diverting from Dillon. They probably have a minimum they must continue to release to the Blue and they balance out demands and other obligations when they schedule releases. Again, we'd have to ask them. The end result, though, was less inflow into Green Mountain. Because we were full and did not have any downstream senior rights or contractors asking for water, our releases scaled back to match the inflow.
It seems to me, this year, west slope storage has done pretty well. It's been much, much drier on the east slope so reservoirs that provide for diversion like Granby or Dillon have been busy. Both William's Fork and Wolford are compromise reservoirs, like Green Mountain--that is to say, they are the result of a compromise between west and east slopes for some east slope diversion. Denver is the operator of William's Fork. The Colorado River Water Conservation District is the operator of Wolford. I do not know what their operating prinicples are or when and why they make releases they do. I only know about William's Fork releases when they are involved in a Green Mountain exchange with us.
I would imagine their releasing rules are similar to ours. Perhaps, like us, they have contracted some of their stored water to water users downstream. Green Mountain was built to compensate the west slope, in part, for the diversions of the Colorado-Big Thompson project over in Granby out of Granby and Willow Creek and Shadown Mountain Reservoirs. The rest of the storage in Green Mountain has just been contracted to downstream west slope users who, when they need it, or when their senior calls come on, we provide water to by releasing it down the Lower Blue.
So, from here on out the cfs coming out of Green Mountain Dam will not be so much because of Dillon and Denver, but because of west slope demand. During the spring run-off, the relationship you described between Bailey and Gore is probable: there are definitely times Bailey being up means Gore is down. But, after run-off, all bets are off because the senior calls and then contracted water for the west slope take precedence.
My guess is that Wolford and William's Fork operate similarly. But, you'll have to ask their owner/operators for a more accurate representation.
Clear as mud, right?
Post again or contact me directly if more questions.
Best,
Kara
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