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Mr. Rick Parsons, P.E. February 10, 2016 <br /> L.G. Everist Combined SWSP <br /> Page 6 of 14 <br /> The period of analysis selected for the 1.41 shares included in this SWSP is 1950 through 1997. <br /> For this period, diversion records for the Rural Ditch were downloaded from Hydrobase using Use 1 <br /> (irrigation) and Source 1 (river). Daily diversions for the Rural Ditch were adjusted to include only the <br /> diversion up to 83 cfs, the sum of the two senior Rural Ditch irrigation rights. The 58-year study period <br /> is representative of wet, average and dry years evidenced in the Saint Vrain Creek and the South <br /> Platte River Basin. The 1.41 shares of the Rural Ditch were historically used on 77-acre Lohmann <br /> property located in the NW1/4 of Section 6, Township 2 North, Range 67 West of the 6th P.M. (Figure <br /> 1). The land historically irrigated by the 1.41 shares is the same land that is currently being mined at <br /> the Carbon Valley Pit. Thus all of the lands historically irrigated by the subject shares have been <br /> permanently dried up due to the mining operations. <br /> The HCU analysis conducted for the 1.41 Rural Ditch relied on the following method and assumptions: <br /> • Modeling using the State CU and the Modified Blaney-Criddle method with the TR-21 crop <br /> coefficients. <br /> • The total structure daily diversion records were limited to the period of proposed April 1 through <br /> October 31. <br /> • Soil Conservation Service methodology for calculation of effective precipitation. The soils on the <br /> Lohmann property include predominantly Heldt silty clay on 1 to 3 percent slopes with some <br /> Aquolls and Aquents gravels. Available water content of the soils as reported by National <br /> Resource Conservation Service ("NRCS") Web Soil Survey averages 0.155 inches per inch. <br /> • Assumed ditch loss of 15 percent. <br /> • Temperature and precipitation data were taken from the Longmont 2 ESE climate station (ID 5116). <br /> The Longmont climate station is located approximately 7 miles from the Lohmann property. <br /> • From a 1999 aerial photo, approximately 34 acres were identified as irrigated on Lohmann <br /> property. This quantification corresponds with information provided in an affidavit regarding the <br /> usage at the Lohmann property (attached to this letter). There appeared to have been additional <br /> consumptive use on the lands marked as questionable on the figure included with the affidavit. <br /> However, these lands are not included in this HCU analysis. <br /> • As noted in the affidavit the land was flood and furrow irrigated and the crops grown were alfalfa, <br /> corn and barley through 1972 and alfalfa and corn thereafter. <br /> • The Applicant proposed a maximum irrigation efficiency of 55 percent for flood and furrow <br /> irrigation for the crops grown on the Lohmann property. <br /> • Return flows assumed to be 33 percent ground water and 67 percent surface water. Ground water <br /> return flow was analyzed using AWAS software based on the Glover methodology according to the <br /> parameters summarized in Table F. <br /> Table F- Summary of Glover Parameters <br /> Distance from Distance from Transmissivity <br /> Farm to River (ft) boundary j o River (gpd/ft) Specific Yield <br /> 2,000 4,173 50,000 0.2 <br /> The HCU results are summarized in Table G. <br /> Table G- 1.41 Rural Ditch HCU Results <br /> Month Jan Feb I Mar Apr May Jun I Jul Aug Sep I Oct Nov Dec Total <br /> Farm Headgate 0 0 0 0.6 16.6 28.2 42.5 27.8 11.1 2.3 0 0 129.1 <br /> Delivery <br />