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" -..' ., 000342 MEMORANDUM TO: Ross Bethel October 15, 1996 FROM: Meg Frantz SUBJECT: "Fresh eyes" critique ofCRDSS New Comments Hinman Creek In the Phase 2 Yampa model, Willow Creek enters the Elk River above Hinman Creek, In reality, Hinman Creek, which is a much smaller trib than Willow Creek, enters the Elk River a mile or two above the Willow Creek confluence, The impact to accuracy in the existing model appears to be minor, related to the fact that there is an instream flow reach on the Elk River from somewhere above the Hinman Creek confluence to somewhere below the Willow Creek confluence, As modeled, that instream flow right always gets the benefit Willow Creek's addition to the stream; in reality, there is a portion of the reach above Willow Creek which might be short when the section bel9w Willow Creek is fully satisfied, Furthermore, there is the potential that a future user might want to add a right in this vicinity and be unable to configure it correctly without changing the existing model. Resolved Comments Boyle has already discussed the following two items with the State, and we have reached resolution on how to handle them in the Phase 3 model. However, the State may want to consider improving these areas in the long term, Bear River Minimum Streamflow In the Phase 2 model, one instream flow structure (582404) was used to cover the Bear River MSF from Stillwater Reservoir to Phillips Creek. Three nodes were used in the model within the reach, According to the water rights tabulation, this stretch ofthe river is governed by two instream flow rights, one for 5 cfs from Stillwater Reservoir to Yamcolo Reservoir, and a second for 12 cfs from Yamcolo to Phillips Creek, The different flow amounts were able to be exerted in the Phase 2 model through the demand file (ifa), which has a separate right and record for each of the three nodes, Thus the first node had a demand of 5 cfs, and the second and third node had a demand of 5 cfs during winter and 12 cfs during summer. (This appears to be an error since we find no indication in the water rights database or the bound tabulation that the Yamcolo-to-Phillips right varies through the year; we believe the correct demand is 12 cfs throughout the year,) Now that we are representing instream flow rights as a reach with only one water right, only one demand can be entered in the .if a file to control the entire reach, In consultation with the State, it was decided to use 12 cfs as the decreed amount in the .ifr file, and a demand of 5cfs in winter and 12 cfs in summer, for structure 582404 in the Phase 3 model, This approach will probably come closest to effecting the same water allocation as the Phase 2 model without adding a new structure, because calls from the downstream BO&,lLE