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checked and refined when RTi finalizes the irrigated acreage assessment for the upper <br />basin water districts. <br />• Mike Sayler asked if any weather data correlation between the South Park and Dan Smith <br />studies were done. Erin Wilson stated that none has been done at this time. <br />• Ivan Walter indicated that the climate data used in the Grand County DWB studies was <br />very suspect -not from on-site stations. <br />• Erin Wilson stated that LRE compared ET at the Dove Creek CoAgMet climate station <br />near Dolores using Penman-Monteith and in the Rio Grande and both sites compared <br />with the high altitude coefficient results. <br />• Dan Smith recently showed good correlation between td,ff(tmaX -tm;,,) and lysimeter results <br />of CU and is now suggesting that a local calibration of crop coefficients for the original <br />Blaney-Criddle include adjustment for td,ff. Dan Smith did provide his initial equations <br />for adjustment of the crop coefficient. This adjustment is not expected to affect the <br />average annual CU results but produce better estimates between various types of years. <br />LRE will investigate the affect of the recommended adjustment. <br />Plains Blaney-Criddle Crop Coefficients <br />• The Kimberly website (www.kimberly.uidaho.edu/water/asceewri~ has two papers by <br />Jim Wright and Rick Allen which provide new sets of slightly different coefficients to <br />use with ASCE Penman Monteith. (Ivan Walter) According to Ivan, the Standardization <br />report that addressed the use of Wrights crop coefficients was written to neither <br />encourage nor discourage their use because of the Arkansas Compact Litigation. Ivan <br />indicated concern over use of the Holyoke station and Jon indicated there would be <br />credibility problem if Holyoke was used because it is not representative of irrigated land <br />in the South Platte. Dan Smith later in the meeting indicated that his investigations in the <br />Gunnison Basin indicated that differences in minimum daily temperatures between <br />agricultural and municipal stations were not very great but he found rather large <br />differences (6-7 degrees F) between maximum daily temperatures. <br />• NCWCD climate stations are situated in irrigated fields and (using less years of data) <br />may be better than using CoAgMet stations (if those CoAgMet stations are not located in <br />irrigated areas. (Ivan Walter) Jon Altenhofen suggested using the NCWCD Crook station <br />over the CoAgMet Holyoke station, which is not located in an irrigated field. <br />• Mike Sayler indicated that he saw a two or three tier set of adjustments when developing <br />crop consumptive uses at an area. First, one needs to locally calibrate a method like <br />Blaney-Criddle to a more accurate method like ASCE Penman Monteith at a nearby <br />agricultural climate station. Second, one needs to transfer that calibration to a longer <br />weather station (i.e. an airport climate station). Mike also indicated that it was important <br />to assess whether there are significant climate differences between the long-term weather <br />station and the site that CU is being investigated at. <br />• Ivan Walter asked if we had considered calibrating ASCE to Hargreaves and then using <br />Hargreaves back in time instead ofBlaney-Criddle. <br />• Jon Altenhofen expressed concern over the proliferation of crop coefficients and <br />indicated that he believed that we should not be generating new crop coefficients but <br />rather a factor(s) that would be applied to the "non-crop" elements of the modified <br />Blaney-Criddle equation (Kt(t*p)/100). This "non-crop" calculation would resemble a <br />reference ET (i.e. ASCE Standardized Penman-Monteith) approach. Once the factor is <br />developed (which he believes would be pretty consistent for a region), then the standard <br />Page A4 of AS <br />