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CRDSS <br />TASK MEMORANDUM 2.09-17 <br />Review of USBR Weather Station and Recommended New Stations <br />For the San Juan River Basin <br />1.0ISSUE <br />Climatic data from National Oceanic and Atmospheric Administrations (NOAA) weather stations are <br />utilized to determine agricultural crop consumptive use in the United States Bureau of Reclamation's <br />(USBR) Colorado River System Consumptive Uses and Losses Report (CULR). In the Phase I <br />CRDSS Task memorandum 1.14-1, it was recommended that the weather station sites be checked for <br />representativeness. This memorandum will serve to meet that recommendation as it pertains to the <br />San Juan River basin. <br />2.0DISCUSSION/ANALYSIS <br />This review of NOAA w eather stations encompasses only those st ations utilized for the San Juan River <br />basin and as reported in the USBR's 1981-85 CULR. Th e stations identified in the appendices of the <br />CULR are listed in Table 1. <br />Subsequent to the 1981-85 CULR, USBR personnel have proposed changes in weather station selection <br />for some of the hydrologic units in Colorado. These recommended changes for the San Juan River <br />basin are summarized in Table 2. <br />Within the San Juan River basin, there are several NOAA weather stations which collect maximum and <br />minimum temperature and precipitation data but we re not utilized in the USBR's 1981-85 CULR or the <br />proposed revisions. These stations are listed in Ta ble 3. The listing includes only those stations with <br />recorded data from 1975. <br />Ideally, agricultural weather stations should be site d in level, open terrain, representative of the local <br />agricultural environment. Unfortunately, most NOAA weather stations are located in urban areas; <br />therefore, temperature measurements may not be representative. Precipitation measurements are <br />influenced more by regional topography; thus, an urban versus an agricultural siting should have very <br />little impact. Site descriptions of the weather sta tions listed in Tables 1, 2 and 3 were provided by <br />Nolan Doesken, Colorado's Assistant State Climatologis t. Review of the descriptions found that most <br />of the sites are located in an urban environment. Five exceptions were noted: Fort Lewis is located at <br />the Colorado State University San Juan Experiment Station; Lemon Dam and Vallecito Dam are located <br />in narrow river valleys; Northdale is located in rolling farmland and Yellow Jacket is located in an <br />orchard. Since the data collected by NOAA is the only data available, these data are recommended for <br />use in CRDSS. This review of representativeness w ill only address the location of the selected weather <br />stations for each sector relative to the location of the irrigated area. <br />Recommended changes to the weather stations used in CRDSS are based upon the following: <br />1.Analysis of the maximum, minimum a nd average temperatures, and precipitation <br />records for the period 1970-90. <br />1 <br />12.3.96 12.09-17 - Walter <br />