SPDSS_Task59-1_Develop Locally Calibrated Blaney-Criddle Crop Coefficients

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Table 4 Average Annual PCU Estimates Using the ASCE Standardized Method and the Modified Blaney-Criddle Method with TR-21 Crop Coefficients Crop Type ASCE BC Difference % Difference Fort Collins (1993-2003 Avera e) Alfalfa 2.27 2.26 0.01 0% Corn Grain 1.57 1.66 -0.09 -6% Dry Beans 1.20 1.48 -0.28 -23% Grass Pasture 2.50 2.10 0.40 16% Small Grains 1.59 1.56 0.03 2% Sugar Beets 1.69 2.00 -0.31 -18% Fort Lupton (19 93-2003 Avera e) Alfalfa 2.66 2.58 0.08 3% Corn Grain 1.86 1.86 0.00 0% Dry Beans 1.39 1.65 -0.26 -19% Grass Pasture 2.88 2.32 0.56 19% Small Grains 1.74 1.64 0.10 6% Su ar Beets 2.17 2.32 -0.15 -7% Greeley (1993-2003 Average) Alfalfa 2.67 2.53 0.14 5% Corn Grain 1.83 1.84 -0.01 -1% Dry Beans 1.35 1.65 -0.30 -22% Grass Pasture 2.85 2.27 0.58 20% Small Grains 1.80 1.66 0.14 8% Su ar Beets 2.10 2.27 -0.17 -8% Sterling (1996-2006) Alfalfa 2.93 2.59 0.34 12% Corn Grain 2.08 1.89 0.19 9% Dry Beans 1.53 1.66 -0.13 -8% Grass Pasture 3.22 2.32 0.9 28% Small Grains 1.94 1.55 0.39 20% Sugar Beets 2.18 2.18 0.00 0% As indicated in Table 4, the ASCE Standardized method produces greater seasonal PCU estimates for certain crops at certain locations while the modified Blaney-Criddle method (with TR-21 coefficients) produces greater seasonal PCU at other locations. Figures 6 through 28, depicting these results on a monthly basis, are provided at the end of the memo. B P In previous DSS efforts, calibration of modified Blaney-Criddle crop parameters was accomplished in two steps; first adjustment of growing seasons and next adjustment of crop coefficients. As noted above, the crop growing seasons are based on frost dates or average Task59_l.doc (updated January 11, 2008) 11 of 32