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Non-Tributary Support: Cash Mine Borehole AdrianBrown <br />C,2+ZZ <br />f Q x Ze a? <br />1 <br />=- <br />7[x1 x12 + z2 . <br />where: f = stream flow depletion per unit length [L2T-1] <br />Q = volumetric flow rate from well [L3T-1] <br />x1 = distance of well from the stream [L] <br />z = distance along stream from point normal to the well [L] <br />a = KD/S = transient change rate parameter [L2T-1] <br />K = hydraulic conductivity [LT-1] <br />D = thickness of aquifer [L] <br />S = storage coefficient [-] <br />t = time since pumping began [T] <br />3. The total change in flow discharging to the -stream is found by computing the streamflow <br />depletion 21, multiplying by the sector length, and summing the sector stream depletionS22. <br />4. The reduction in stream flow as a percentage of the flow extracted in dewatering the mine is <br />computed by dividing the change in flow discharging to the stream by the dewatering flow rate <br />at the mine. <br />The computations described above are presented in Table 5 for the Cash Mine dewatering flow. <br />Table 5 - 100 Year Stream Depletion due to Cash Mine Dewatering <br />Sector 1 2 3 4 5 6 Total <br />Time (t) years 100 100 100 100 100 100 100 <br />Flow (Q) cuft/yr 109617 109617 109617 109617 109617 109617 109617 <br />Hydraulic conductivity (K) ft/yr 0.178 0.178 0.178 0.178 0.178 0.178 0.178 <br />Depth (L) feet 647.8 647.8 647.8 647.8 647.8 647.8 647.8 <br />Storage coefficient (S) 0.05 0.65 0.05 0.05 0.05 0.05 0.05 <br />Distance (x1) 4083 3571 2848 2555 2742 4083 varies <br />Length (z) W 1540 1157 822 461 633 787 5400 <br />Stream depletion 0.0002 0.0112 1.5289 5.3170 <br />- 2.3246 <br />- <br />- 0.0001 <br />- 9.1820 <br />Stream depletion/Q O.0000 0.0000 0.0014 0.0049 <br />, 0.0021 T <br />0.0000 0.0084 <br />21 The maximum stream depletion rate is used for each sector, by setting z = 0 in the equation for the stream depletion per unit length. Thus <br />the values provided represent an over-estimate of the actual depletion. <br />22 Strictly speaking, the Glover equation applies to an infinitely long straight stream. The segmented approach used here for conditions <br />where the stream is not straight is considered to somewhat over-estimate the actual depletion, as it uses the maximum stream depletion <br />rate for each segment considered, assuming that the segment is normal to the dewatering location. <br />1601A-20070125 10