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Mr. Don West, P.E. Re: Substitute Water Supply Plan for the Jesse Lee Pft M-84-043 October 30, 1006 Page 2 of 4 Evaporative Losses Evaporation losses will result from the existing ponds and a gravity fed drainage ditch that will expose groundwater on the site. The, ponds will expose approximately 1.07 acres of water. The drainage ditch is approximately 350 feet long and approximately two feet wide and gravity drains any water trapped within the pit to the existing ponds. The drainage ditch exposes approximately 0.02 acres of water surface area. The total exposed surface area at the Jesse Lee Pit is 1.1 acres. To calculate. the evaporative consumptive use, the NOAH Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States (U.S. Department of Commerce) was used to determine gross evaporation For this location, the gross annual evaporation is 39 inches. Monthly evaporation percentages as suggested by the Office of the State Engineer were used to calculate monthly evaporation. The precipitation values used , to calculate evaporative consumptive use were obtained from the climate data available through Colorado's ' Decision Support System website (http://cdssstate.co.us/DNNn. Annual precipitation at this site was assumed to be equal to that recorded at the neazest weather station, Buena Vista (Station ID 1071), which is 10.3 inches for a period of record from 1948 to March 2006. Effective precipitation was calculated as 70 percent of total precipitation. Net evaporation was then computed as the difference between gross evaporation and effective precipitation. Based on the information presented above, the annual evaporative consumptive use equals 2.92 acre- feet. The annual evaporative consumptive use calculations can be viewed in Table-1. Operational Losses Operational losses at the site consist of water lost in product hauled off-site and water used for dust control The maximum annual production for the pit is estimated at 50,000 tons of Taw material. The moisture content of the material hauled off-site was assumed to be four percent by weight. The total annual consumptive use for dust control will be approximately 1.0 acre-foot. Table-2 shows the monthly consumptive use distributed throughout the year using the same percentages as the production of the aggregate mined. The total operational consumptive use for the Jesse Lee Pit is 2.473 acre-feet per year. The total consumptive use for January 2007 to March 2007 totals 0.96 acre-feet. The total annual consumptive use for the 2008 Water Year totals 5.39 acre-feet. The total consumptive use calculations can be viewed in Table-3: PROJECTED STREAM DEPLETIONS Because the exposed surface area at the Jesse Lee Pit site is set back from the river, the depletions were not assumed to be instantaneous. A stream depletion model was completed for the well to display the lagged effect of the depletions (Please see Appendix A). A summary of the monthly stream depletions can be found in Table-3. Tlie stream depletion model for the well was developed under the followitig assumptions: • The exposed surface area is an average of 250. feet from an active stream.