SPDSS_Task59-1_Develop Locally Calibrated Blaney-Criddle Crop Coefficients

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Table 3 CoAgMet and NCWCD Climate Stations Station Name Source Identifier Water District Elevation (feet) Period of Record i Fort Collins CoAgMet FTCO1 3 5,120 1993-2003 Fort Lu ton ~ CoA Met FTLO1 2 5,055 1993-2003 Greeley CoAgMet GLY03 3 4,680 1993-2003 Sterling 3 NCWCD Sterling 64 3,938 1996-2006 ' Calibration at the Fort Collins, Fort Lupton, and Greeley stations was performed in 2004, based on 1993-2003 period of record. Calibration at the Sterling station was performed in 2007, based on 1996-2006 period of record. ~ The Fort Collins climate station was s Elevation information not available from NCWCD website; estimated based on NOAA climate station location. The analyses were based on the full available period of record. The daily climate data were inspected and, based on discussions with CoAgMet, negative values of solar radiation and vapor pressure were removed. There were also instances where the wind data had a value of 15.45 km/day for multiple days in a row. This is an unreasonably low wind value and because of the repeated days in a row with the same value and based on discussions with CoAgMet personnel, these data were also removed. Guidelines from "The ASCE Standardized Reference Evapotranspiration Equation" (ASCE, 2005) were used to inspect and adjust the daily climate data. The daily climate data were generally very complete during the growing season of April through October throughout the analysis period. The Fort Collins station was over 97% complete for all parameters, Fort Lupton was over 99% complete for all parameters, Greeley was over 98% complete for all parameters except wind which was around 79% complete, and Sterling was 100% complete for all parameters. Missing daily data were filled using linear regression techniques described in the SPDSS Task 53.2 Collect and Fill Monthly Climate Data memo. Following is a summary of that analysis for the four comparison stations: • Selection of climate stations providing the raw data to fill another climate station data set was based on proximity of the stations resulting in similar climatic conditions, amount of data that could be filled, and the relative correlations between the two data sets. • The unfilled Greeley climate station data was used to fill both the Fort Collins and Fort Lupton climate data and the unfilled Fort Lupton climate station was used to fill Greeley. The monthly correlation coefficients (R) generally fell in the range of 0.70 to 0.99. There was a small amount (around 0.5% or less for each parameter at each climate station) of missing data that could not be filled using regression because concurrent data were not available at both climate stations. Therefore, the remaining missing data were filled using linear interpolation. The calibrated coefficients resulting from this task will be applied to the SPDSS key climate stations using the monthly NOAA data stored in HydroBase. However, for consistency with the data used in developing the calibrated coefficients with the ASCE Standardized and modified Blaney-Griddle methods, the average monthly temperature data used with the modified Blaney- Task59_l.doc (updated January 11, 2008) 9 of 32