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. . Memo to Colorado Water Conservation Board Members From: Peter Evans and Gene Jencsok Date: October 17, 1995 SUBJECT: Agenda Item 2, October 20, 1995 Board Meeting Endangered Fish Recovery ISF Water Right - Colorado River (Mainstem) Page 8 endangered fish. The total instrtam now appropriations suggested in Table 4 arc no grealcr on average: than will flow out ofstate under the compacts. The: more: significanl challenge: will be in arriving at monthly or daily distributions for thc:~ annual amounts which protect both water development opportunities and the: needs of the endangered fish given the variable: hydrology which oecUM: both annually and seasonally. Also, the: slruclurc: and format oflhc: water right application will be important. particularly in light ofthc: recent decision in the: AJfNn Wi/tUrMn Workshop, Inc. ". The Colorado Walf!r Conservation Board (Snowmass Creek. Case). "H. OUf recommended approach does not foreclose any rasonablc: development opportunities within Colorado's compact apportionment. As suggesled in the CWCB's Statement of Policy and Procedure, it presumes that within the time: it will lake: to fully develop the recommended range: of new consumptive uses, new information about the endangered fISh will become available such that the CWCB and others will find it necessary to reevalua1e the si(uation and the state"s needs. The open process employed in assembling Utese recommendations, facilitated through the suppon of the CWCB's staff and others, is helpful in promoting the use of the best informalion available and enabling a div~c: group of interested parties to participa1e in policy fonnulation. However, the:re: are limits to what can be expecled from a group representing statewide interests, md the organization ofsimilac groups within the: principal subbasins should also be pursued in order to fine tune the information." We have reviewed these observations and recommendations, and have taken them into consideration in the development of our recommendation. Phvsical Water Availability Study. Before the CWCB can appropriate an instream flow water right, it must determine that water is physically available for the appropriation within the proposed instream flow segment. Water availability studies for the 15 Mile Reach have been conducted using hydrologic and water rights administration records from the Cameo Gage, which is located upstream of the proposed instream flow segment. Streamflow records for the 1970- I 992 period were evaluated and adjusted to reflect current (1992) levels of depletion. Daily and average monthly flows were analyzed statistically, and daily and monthly flow duration curves were plotted. In addition, annual volumes and annual peak flows were tabulated, statistical distributions were calculated, and flow duration curves for the annual volumes and annual peak flows were plotted. These curves can be used to determine what percentage of the time a given daily flow, monthly flow, annual volume, or annual peak flow would occur during the adjusted 1970-1992 period in the IS Mile Reach. This information is documented in a report entitled Colorado River - J 5 Mire Reach. Physical Water Availability Study and dated August 30, 1995, ~- Other Efforts to Restore and Protect Flows in the IS Mile Reach. It has become obvious that restoration and protection of flows which "mimic" the natural flow regime for the 15 Mile Reach cannot be accomplished through the appropriation of junior water rights, Management of water resources upstream from the IS Mile Reach for consumptive and non-consumptive uses have substantially altered the natural flow regime. Furthermore; there are many conditional water rights (approximately 3,6 million acre-feet of storage rights and 90,500 cfs of direct flow rights) which will be senior to the proposed 1995 fish recovery instream flow water rights, If developed, these senior rights would take priority in the allocation of available water and could significantly reduce the existing flows in the IS Mile Reach. Therefore, the Recovery Program has initiated several supplemental efforts to improve flow conditions in the 15 Mile Reach. These supplemental efforts include agreements for the