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used to estimate pumping as an alternative to using a totalizing flowmeter (TFM) to directly <br />measure pumping. PCCs must be determined utilizing rating procedures approved by the State <br />Engineer and conducted under supervision of an individual/entity annually approved by the State <br />Engineer to conduct such tests. The PCC rating must be updated at least every four years. <br />Research conducted by the USGS (Troutmann, et al) on the Lower Arkansas River Basin showed <br />that PCCs developed in year one tend to overestimate pumping when applied to future years' <br />power consumption (as compared to pumping measured using totalizing flowmeters). The <br />USGS found a potential difference in pumping amounts calculated using the PCC approach and <br />those measured with a TFM to vary by 2.2 percent per year, without considering variability due <br />to pumping water level changes. An additional 1.6 percent per year difference was observed due <br />to the lag between the year the PCC measurement was made and the year pumping was <br />estimated. The USGS study estimated total network pumping for 1,000 wells using both <br />approaches and found the calculated PCC pumping to be 8.4 to 11.3 percent greater than the <br />measured TFM pumping for afour-year lag time and from 3.9 to 6.4 percent greater for atwo- <br />yearlag time. <br />The proposed Rules Governing the Measurement of Ground Water Diversions Located in Water <br />Division No. 3, The Rio Grande Basin are recommending more strict requirements with the PCC <br />approach than outline under the Arkansas Rules: 1) the PCC approach must produce results <br />within +/- 5 percent of the actual volume pumped over the calendar year, 2) PCC ratings must be <br />determined by at least two ratings during the course of a single irrigation season with a minimum <br />interval of 90 calendar days between each rating, and 3) PCCs must be updated at least every two <br />years. <br />Over the past twenty years, the State has found that the PCC approach does not have long-term <br />accuracy and additional conditions are needed to ensure pumping estimates made using the PCC <br />approach remain accurate. Given these findings and the scope of the SPDSS, it was determined <br />that power data would only be used to estimate pumping if PCCs associated with the specific <br />dataset are provided. <br />Power records available through the Colorado State University archives were considered. Based <br />on information provided by Bob Longenbaugh, two potential sources of information were <br />identified: <br />1. Annual power records from the 1930's through the mid- 1970's, as reported by individual <br />power companies. These records are not associated with individual wells but rather <br />provide the annual power records on a regional county basis. There is no simple way to <br />associate the regions with specific acreages and crop types. The records are reported in <br />kilowatt-hours and do not include PCCs. Further, the records are annual and do not <br />provide monthly distributions. <br />2. Monthly power records from around 1945 through 1965 for Morgan County associated <br />with unique identifiers that correspond to individual wells. The records are reported in <br />kilowatt-hours and do not include PCCs or associated acreages and crop types. <br />Task 77.doc 4 of 8 <br />