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PCU Difference (NOAH -NCWCD) <br />1 <br />50 <br />. <br />,.., 1.00 <br />w <br />v <br />c <br />w <br />v <br />c <br />w <br />`w <br />D <br />U <br />a 0 <br />50 <br />. <br /> <br />0 <br />00 <br />. <br />o`O o`O o~ o~ o0 00 00 00 00 0o p~ o~ p`ti p`ti o`~ o`~ off` off` o~' <br />~a~ ~o~ ~a~ ~~ ~a~ ~~ ~a~ ~~ ~a~ ~~ Sao ~~ Sao ~~ ~a~ ~~ ~a~ ~~ ~a~ <br />Figure 1. Differences in PCU at Sterling NOAA and NCWCD Climate Stations. <br />Further investigation of the locations of key NOAA climate stations used to estimate ET <br />in the highly irrigated areas of Water Districts 1, 2, and 64 showed that 60 percent of the <br />stations are urban and 40 percent of the stations are rural. However, 13 of the tota126 <br />key NOAA climate stations used for SPDSS are in an agricultural setting. SPDSS <br />consumptive use analyses are basin-wide, and a primary goal is to determine procedures <br />that can best be applied throughout the basin. Therefore, although the difference in <br />potential consumptive use reflecting the "urban heat island effect" shown in Figure 1 is <br />noted, we did not revise our original approach and calibration efforts used the same <br />climate data for daily and monthly calculations. <br />Revised ASCE Standardized Penman Monteith Coefficients -The SPDSS calibrated <br />coefficients were developed using the ASCE Standardized Penman Monteith method <br />with crop coefficients developed by Wright and provided in Table 6.9 of ASCE Manual <br />70. The Kimberly website (www.kimberly.uidaho.edu/water/asceewri/) has two papers <br />by Jim Wright and Rick Allen that provide new sets of slightly different coefficients to <br />use with ASCE Penman Monteith. These papers were not available during the calibrated <br />coefficient efforts. According to "The ASCE Standardized Reference Evapotranspiration <br />Equation" prepared by the Task Committee on Standardization of the Reference <br />Evapotranspiration of the Environmental and Water Resources Research Institute of the <br />American Society of Civil Engineers in 2005 (page 47), the mean crop coefficients <br />reported by ASCE Manua170 for use with alfalfa reference can be used directly with the <br />ASCE Standardized method "for most practical applications." In addition, we re-ran the <br />Page 6 of 7 <br />