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<br />b <br />C =aQ <br />r r' <br /> <br />(4) <br /> <br /> <br />002457 <br /> <br />was included in the model, an estimate of the increased amount of <br />be needed. At present, these numbers would be difficult <br />Therefore, it was assumed that the amount of water moving through <br />during existing conditions was the same amount moving through the <br />an anticipated mining activity except for dewatering activities. <br /> <br />water would <br />to obtain. <br />the system <br />system with <br /> <br />At each node the surface-water quality component, mean monthly <br />dissolved-solids concentration in milligrams per liter, is calculated by the <br />mass balance equation: <br /> <br />n n <br />ci=[( I QuCu)+QrCr]/[( I Qu)+Qr]' <br />u=l u=l <br /> <br />(3) <br /> <br />where: C.=dissolved-solids concentration at node i, <br />1- <br />n=number of nodes immediately upstream from node i, <br /> <br />Q =discharge at nodes immediately upstream from node i, <br />u <br /> <br />C =dissolved-solids concentration at nodes immediately upstream from <br />u node i, and <br /> <br />C =dissolved-solids concentration associated with the incremental <br />r <br />discharge (Q ) within the reach. <br />r <br /> <br />The dissolved-solids concentration within the reach <br />from the linear-regression equation: <br /> <br />(C ) <br />yo <br /> <br />is obtained <br /> <br />where: a and b=the regression coefficients from simple linear regression. <br /> <br />Initial estimates of C are obtained from observed data at each node. <br />yo <br />For input nodes, the observed data reflect the actual value of C because it <br />is the integrated dissolved-solids concentration for the total feach above <br />that node. However, for internal and output nodes, observed data do reflect <br />integrated dissolved-solids concentration for the total length of stream <br />above the node and do not reflect the reach between nodes. Thus, the observed <br />data are not an estimate of C. Because data are not available to estimate <br />C directly, final estimat~s of the regression coefficients in equation 4 <br />w~re obtained in the calibration process. <br /> <br />For each anticipated mining activity, the Mined Land Reclamation Divi- <br />sion estimated dissolved-solids concentration for water discharging to the <br />stream from the mining activity. During mining operations, the concentration <br />value of dissolved solids was 2,860 mg/L (milligrams per liter) for combined <br />surface- and ground-water discharge. For postmining situations, no discharge <br />from a surface-water source was assumed, and the dissolved-solids concentra- <br />tion was estimated at 3,200 mg/L from a ground-water source only. <br /> <br />7 <br />