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Show APPENDIX G RESERVOIR EVAPORATION An immediate cause for the undertaking by the Engineering Department of the Commission of the independent investigation of probable evaporation loss from reservoirs lay in the question whether a large increase in loss by evaporation would take place if the Gray Canyon, Desolation or Dewey reservoir sites were substituted for the Echo Park site proposed in the Colorado River Storage project report. Furthermore, Article V of the Upper Colorado River Basin Compact, paragraphs (.a) and (b), contains provisions concerning "losses of water occurring from or as a result of storage in reservoirs." Section (a) provides that "Water stored in reservoirs covered by this paragraph (a) shall be for the exclusive use of and shall be charged to the State in which the reservoir or reservoirs are located." By the proper application of the inflow-outflow method, losses from existing reservoirs will be automatically included in the stream depletions in the drainage where such reservoirs are located, since such depletions will be measured at state lines. However, new reservoirs proposed for construction and use as irrigation and power development takes place in the Upper Basin will involve several considerations which will require very extensive and careful investigation. These considerations arise in connection with paragraph (b) of Article V which states in part "All losses of water occurring from or as the result of the storage of water in reservoirs constructed after the signing of this Compact shall be charged" in accordance with the provisions of subparagraphs (b) (1) and (b)(2). In undertaking this investigation, the basic data on evaporation in the Upper Colorado River Basin which was collected, tabulated and analyzed under the direction of the Engineering Advisory Committee to the Upper Colorado River Basin Compact Commission was checked and used, except that in a few cases, where evaporation records were available for years subsequent to 1945, the data were brought up to date. Such was the case with the Weather Bureau Stations at Farmington, New Mexico, and Montrose, Colorado. The results of the Engineering Advisory Committee investigations are available in the final report of that committee to the Upper Colorado River Basin Compact Commission in the form of curves for the principal subdivisions of the basin and the Bureau of Reclamation engineers used these curves in their reservoir operation studies to determine the probable loss due to evaporation from the reservoirs proposed in the report on the Colorado River storage project. -43- |
