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replacement of the evaporation losses is therefore about 4.6 acres. The location of the <br /> current, 1990, water surface area is shown on the attached Figure B-1. <br /> The net evaporation losses from the 4.6 acres of exposed water surfaces were- <br /> estimated in accordance with the guidelines and criteria developed by the State Engineer. <br /> The annual gross evaporation for shallow lakes in the Fort Collins area was derived from <br /> NOAA Technical Report NWS 33 and is estimated to be about 40.0 inches (333 feet). The <br /> annual evaporation was then distributed on a monthly boxis using the pamentagm <br /> recommended by the State Engineer. Finally, the pet monthly evaporation loss was <br /> determined by subtracting 70% of the measured precipitation at the Fort Collins weather <br /> station. The monthly values for the calculated monthly gross evaporation, the effective <br /> precipitation and the net evaporation losses are shown in Table B-1. For the 4.6 acres of <br /> exposed water surface, the annual evaporation loss is estimated to be about 11.4 acre-feet <br /> Other Losses Incidental to the Wmitury Oauation <br /> Other activities associated with the sand and gravel mining operation which <br /> 'consumptively use water generally include (a) water used to wash silts and fines from the <br /> aggregate, (b)water carried away from the pit with the final product and (c) water used for <br /> dust suppression and control. Since the Challenger Pit is not being operated, there are no <br /> incidental water uses pertinent to the mine operation. Accordingly, the total replacement <br /> requirement relates solely to the evaporation loss from the exposed water surfaces or about <br /> r 11A acre-feet per year. Table B-2 summarizes the monthly replacement requirements. <br /> r <br /> Since all of the mining areas are immediately adjacent to the $xCaWw-1a_Paudrrend <br /> because the river sands are highly permeable, it is assumed that the depletive impact on the <br /> stream will occur in the same month as the water is consumptively used,i.e.,it is assumed that <br /> there is no lag in the timing of the depletions <br /> 2 <br /> -r <br /> r -` r <br /> e <br />