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The purpose of a historic use analysis is to compare the water requirements of the crops <br />grown to the available water. The available water is limited by the efficiency of the irrigation system, <br />which includes trar,~sportation losses and return flows from the irrigation method used on the'farm. <br />Transportation losses in the Boxelder, as discussed previously, are estimated at 10%. The irrigation <br />efficiency on the 'Cimnath Pit property is estimated for flood irrigation to be 60%, based on <br />interviews with John Weitzel .and engineering judgment. Table 3.3 compares the average annual <br />calculated, or potential, consumptive use (calculated CU), potential irrigation water requirement <br />(potential IWR) and the actual consumptive use (actual CU) of Boxelder water on each irrigated <br />parcel and the farrri total. The calculated CU is the total potential consumptive use of irrigation <br />water by the farm a;> calculated by multiplying the CIR from the Blaney-Griddle analysis by the total <br />irrigated area of the farm. The potential IWR is the calculated consumptive use divided by the <br />irrigation efficiency of the farm (60%). The actual consumptive use is equal to the calculated CU of <br />the farm when the delivery exceeds the potential IWR, and the delivery times the imgation efficiency <br />when the potential :[WR exceeds the delivery. <br />Table 3.3 Historic Delivery, Calculated CU, Potential IWR and Actual CU of Timnath Pit. <br /> ~ luiQated Area <br />h Farm Head~ate <br />~` Calculated Potential A~laal CU <br />Parcel ~ ~ <br />- - - ~teres) Deli~en~ AF) _Ci1 (AFB ' I«'R (~1_~ ___ (~N) <br />Northeast Field 70.1 - N/A 104.6 174.4 56.2 <br />Southwest Field 20.6 N/A 30.8 51.2 16.5 <br />Irrigated Pasture 151.7 N/A 226.4 <br />- 377..3 <br />- I2I.6 <br />7~otal ~-t`' ~a - -- <br />-- ZS?.0 361.8 60?.9 19._3 <br />4.0 SUBSTITIJ~TE WATER SUPPLY PLAN <br />4.1 Evaporative and Operational Losses <br />DKC intends to use the Boxelder shares connected with the property to replace depletions <br />related to the opera~~tion of the Timnath Pit. Currently the depletions from the pit are evaporative <br />losses from exposed. ground water, water lost in mined product, and water consumed by dust control, <br />gravel and concrete equipment washing. It is our understanding that gravel and concrete sales occur <br />all year, but they effectively cease during the winter months of December, January, and February <br />when mining and stockpiling operations occur. Thus the operating season considered in the analysis <br />is .from March through November. <br />Outlined in this section of the report are assumptions made regarding the depletions caused <br />C:\Projects\CODKC01\Admin\DKC 2006 SWSP Application.doc 7 Scott Water Engineers, LLC <br />