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SPDSS Task 58 Memo <br />August 5, 2004 <br />Page 7 of 22 <br />White and Yampa River Basins (Division 6~ <br />The predominant method employed in Division 6 for consumptive use analysis is the modified <br />Blaney-Criddle method. The Division 6 Engineer could not recall any method other than <br />modified Blaney-Criddle applied in the White or Yampa River Basins. The Division Engineer's <br />Office relies on the SEO for calculations to check consumptive use estimates submitted with <br />water right change applications. Lysimeter studies performed through the Division Engineer's <br />Office (see subsequent discussions on "Division 6 Lysimeter Program") are available as a <br />secondary check for consumptive use calculations. <br />San Juan/Dolores River Basins (Division 7~ <br />The predominant method employed for consumptive use calculations in Division 7 is the <br />modified Blaney-Criddle method with elevation adjustment. However, the engineering <br />consultant interviewed in this Division indicated that often one can use previously generated <br />consumptive use information, such as from Definite Plan Reports on the Dolores or Las Animas <br />Projects, rather than generate unique consumptive estimates for a prof ect. The Division Office <br />typically relies on the SEO to provide consumptive use calculations to check values in water <br />right applications made in Division 7. <br />State Engineer's Office <br />As indicated by the above discussions many of the State's Water Divisions rely on the State <br />Engineer's Office staff to perform consumptive use calculations (rather than perform those <br />calculations at the Division level). The primary present consumptive use tool presently used for <br />simple consumptive use analyses at the State Engineer's Office is the spreadsheet developed by <br />Keith Vander Horst that performs consumptive use calculations based on the modified Blaney- <br />Criddle method (with adjustment for elevation) and average annual climate data (see DWR TR21 <br />spreadsheet discussion in the model section of this memo). For more robust (i.e. multiyear, <br />multicrop, different PCU methods or database centered) analyses of consumptive use, the official <br />State model for consumptive use analysis, StateCU, is or will be a more appropriate tool than the <br />DWR TR21 spreadsheet model. <br />T,awn ~TraCC <br />In June, 1988, the Colorado State Engineer's Office (SEO) recommended that modifications to <br />the modified Blaney-Criddle method, suggested by Pochop, Borrelli and Burman (1984), be <br />implemented when estimating the PCU of lawn grass and alfalfa. The recommendation as it <br />applied to alfalfa was later withdrawn by the SEO in 1989 at the request of Mr. Pochop. The <br />suggested modifications to the modified Blaney-Criddle for calculating lawn grass consumptive <br />use were 1) new crop coefficients (K~) of .97 in April, 1.0 in May, 1.10 in June, 1.06 in July, .98 <br />in August, .97 in September, and .89 in October; 2) a revised temperature coefficient equation as <br />.00328 x Temperature + .65011; and 3) the application of an elevation correction factor of 2.9 <br />percent for each 1000 feet over the base elevation of 4,129 feet msl for the months of April, <br />May, September and October and a 2.3 factor applied during the months of June through August. <br />This recommendation for altitude correction only applied to lawn grass. This method is <br />