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~ a r":) ~ W ""' The action area the USF&WS considered in the 1991 RPA included the entire San Juan Basin (Water Districts 29, 30, 31, 32, 33, 34, 46, 77, and 78 in Colorado), However, depletions in Water District 32 were not considered as depletions to the San Juan Basin as those depletions are generally satisfied by water imported from the Dolores River Basin, The purpose of this memorandum is to set forth the supporting information we propose to supply to the USF&WS to quantify the historic diversions and consumptive uses occurring in the San Juan Basin as of October 25, 1991 and to supply the USF& WS with an indication of how those depletions might have changed since 1991. The USF&WS desires this added information for consideration in studies that are part of the seven years of research that are being conducted under the SJRRlP and for consideration in developing the long term reoperation guidelines for Navajo Dam, This information is being presented to the water users in the San Juan Basin for review and comment prior to providing it to U,S, Fish & Wildlife Service, Additional copies of this information are available from the Colorado Water Conservation Board, Colorado Division of Water Resources-Division Engineer in Durango or the Southwestern Water Conservation District. We would appreciate any comments by August I, 1997, Approach In October, 1991 we supplied consumptive use values to Reclamation taken from "A report of the water resources of the San Juan River Basin in Colorado," prepared by Clifford H, Jex in December, 1959, Given the time schedule we had to meet for the ALP Biological Opinion, there was simply not time to do a detailed investigation, Values from the Jex report were recommended after comparing them to other sources of information which covered only parts of the basin or were not as detailed, Comparisons to other data sources indicated that while changes had occurred, the net effect on Colorado's overall depletion was not very large, Therefore, the decision was made to use the most detailed data published on a consistent basis rather than use a mix of more current estimates without the opportunity to review the more current estimates in detail and for mass balance in the basin, Attachment 1 contains the information we supplied in 1991. In this review of the historic consumptive use values supplied for the 1991 baseline, we have utilized data from the Colorado River Decision Support System (CRDSS), Our approach was follows: 1. We utilized the State Engineer's water rights tabulation and extracted the net absolute water rights existing as of October 25,1991 by water district. We also did the same for all absolute water rights in the tabulation upto October 31, 1995, Generally, wells were not included as part of this effort if not decreed, 2, Using the State Engineer's diversion records, we then added the following information to the abbreviated tabulation of water rights developed in step I, . Average annual diversion in acre-feet during the period WY 1981 to 1991. . Maximum diversion in a single year in acre-feet during the period WY 1981 to 1991. 2