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The gross annual evaporation for the described cell lakes and dewatering ditch was calculated according <br /> to the NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States using the <br /> isopleths of annual shallow lake evaporation for Colorado. The gross annual evaporation was distributed <br /> on a monthly basis according to the Guidelines and adjusted by effective precipitation per State Policy No. <br /> 2004-34. Table 2, below, displays the calculated unit evaporation, the combined surface area of the <br /> exposed groundwater, and the monthly net evaporation estimated for the years 2017 and 2018. The <br /> attached Table C-1 provides additional detail regarding calculation of the monthly unit evaporative losses. <br /> Table 2 <br /> Evaporative Losses from Exposed Groundwater <br /> Net Unit Area of Net <br /> Month Evaporation Exposed Evaporation <br /> (AF/acre) Groundwater (AF) <br /> (acres) <br /> January 0.00 36.90 0.00 <br /> February 0.00 36.90 0.00 <br /> March 0.00 30.35 0.00 <br /> April 0.13 23.80 3.00 <br /> May 0.27 23.80 6.35 <br /> June 0.37 23.80 8.74 <br /> July 0.33 23.80 7.97 <br /> August 0.26 23.80 6.17 <br /> Septembe 0.23 23.80 5.45 <br /> October 0.15 23.80 3.50 <br /> November 0.01 30.35 0.16 <br /> Decemberl 0.00 36.90 0.00 <br /> Annual 1 1.73 1 33.18 1 41.33 <br /> Note: Dewatering of Cell 4 would begin in March and continue through <br /> November. Calculations assume that the average acreage of Cell 4 pond <br /> during March and November equals'/2 its maximum surface area. <br /> 2.2.2 Water Removed by First/Intermittent Fill <br /> The General Guidelines for Substitute Water Supply Plans for Sand and Gravel Pits state that depletions <br /> must also account for water removed from the stream system by the "first fill" or "intermittent fill' of the <br /> gravel pit. The Guidelines define first or intermittent fill as the water that fills an unlined gravel pit and <br /> occupies the volume previously occupied by the mined material. According to the Guidelines, depletions <br /> associated with the first fill should be calculated according to the following formula: <br /> Vfif= (Vmm- Vbf) * (1 -porosity) - Vlp <br /> 4 Policy 2004-3: Use of Evapotranspiration Credit within Substitute Water Supply Plans Involving the Exposure of <br /> Ground Water in Ponds or Reservoirs not located within the Stream Bed. Office of the State Engineer, 2/27/2004. <br /> 3 :::::RESOURCE <br />