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Mr. David Heintz Page 5 of 10 <br />Duckworth SWSP <br />May 6, 2015 <br />the terms of the previous SWSP the Applicant was required to justify the claimed irrigation <br />efficiency. As requested by the previous SWSP the Applicant was required to justify the <br />claimed irrigation efficiently and must provide all assumptions and information used in <br />the consumptive use model. <br />Based on the information provided by the Applicant's water consultant on April 10, <br />2015 the irrigation type for the Heaton parcel was a mix of graded border irrigation and <br />furrow irrigation for alfalfa and corn. Rosie and Anthony Heaton lived on the Heaton Farm <br />since 1950. They stated that 50 percent of the years alfalfa was grown on the farm and the <br />other 50 percent they grew corn on the farm. The Applicant proposed a maximum 65 percent <br />efficiency for this parcel. According to the Applicant the efficiency was based on review of <br />aerial photos of the farm, lengths of the irrigated land fields, field slopes and the layout of <br />the irrigated farm, the type of irrigation practice and soil type. According to the applicant's <br />water consultant the soils consist of Bankard sandy loam soil prior to mining and are classified <br />as having slopes of 0 to 3 percent, with a soil intake family 3. The irrigation slope of the <br />Heaton Property is approximately 0.3 percent from the south to north based upon review of <br />local topographic map. Based on the SCS Colorado Irrigation Guide the irrigation efficiency for <br />the graded border irrigation with a soil intake family 3 and a slope of 0.3 percent is between <br />65 to 70 percent and the irrigation efficiency for furrow irrigation with the slope of 0.3 <br />percent is 70 percent. Based on the above it is the Applicant's water consultant opinion that <br />the maximum irrigation efficiency of 65 percent is justifiable for the purpose of this SWSP. <br />However, we note that variables other than irrigation method, soils and slopes affect <br />irrigation efficiency. The Applicant did not adjust their claimed maximum potential <br />application efficiency to account for these other variables. Any renewal request for this <br />SWSP must include a maximum efficiency that considers the site specific potential <br />efficiency and the effects of installation, management and maintenance of the irrigation <br />system on the potential irrigation efficiency. in addition, the SWSP request must clearly <br />define how the maximum irrigation efficiency was determined, including all assumptions <br />and calculations. <br />Based on the 1911 through 1998 farm headgate deliveries, the annual on-site <br />depletions attributable to the two Rural Ditch shares were calculated to average <br />approximately 90.1 acre-feet/year. The historic return flow obligations must be maintained <br />and are equal to 73.3 acre-feet, which is comprised of 35 percent surface runoff and 65 <br />percent deep percolation. The timing of the deep percolation return flow was determined <br />based on the Glover Analysis with the following aquifer parameters: Transmissivity= 35,000 <br />gpd/day/ft, the distance from the centroid of the Heaton property to the Boulder <br />Creek -1,200 feet and the storage coefficient =0.1. The transmissivity and the storage <br />coefficient were obtained from a nearby ground water pump test as published in the <br />Groundwater Circular No. 11 data. <br />The HCU results are summarized in table below: <br />Month <br />Jan <br />Feb <br />Mar <br />Apr <br />May <br />Jun <br />Jul <br />AugSep <br />Oct <br />Nov <br />Dec <br />Total <br />Farm <br />Headgate <br />Delivery <br />0.0 <br />0.0 <br />0.0 <br />0.9 <br />18.8 <br />38.9 <br />51.1 <br />32.9 <br />16.0 <br />4.6 <br />0.1 <br />0.0 <br />163.4 <br />On Farm <br />Depletion <br />of <br />1 0.0 <br />1 0.01 <br />0.01 <br />0.6 <br />1 10.2 <br />121.3 <br />28.0 <br />1 18.7 <br />1 8.7 <br />1 2.5 <br />1 0.1 <br />1 0.0 <br />1 90.1 <br />