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MODEL CALIBRATION AND SIMULATION <br />• <br />1) Target head -The only data on Trout Creek Sandstone water levels within the <br />regional basin were obtained from the Seneca IIW test and observation wells <br />(test well steady-state water level = 7232 feet AMSL). However, an <br />unpublished thesis (Stewart, 1983) and structural data found in Bass et al <br />(1955), provided some information concerning the top of the sandstone and <br />the configuration of the potentiometric surface (Figures 3a and 36). <br />2) Recharge -The main parameter adjusted for steady-state calibration was the <br />recharge rate. The recharge rate chosen for best fit with one target well is .21 <br />in/yr. This value does not represent the actual recharge rate in the outcrop <br />areas. It does, however, represent that calibrated in the model, based on <br />transmissivity of the Trout Creek and grid size in recharge areas. Because the <br />• grid blocks represent a larger azea than the actual outcrop area, the actual <br />recharge rate for the Trout Creek Sandstone outcrop area is probably greater. <br />3) Constant Heads - The heads at the constant-head nodes along the <br />downgradient boundary were adjusted to ensure that water exited the model <br />from these nodes, i.e. flow is to the north. Constant-head nodes were placed <br />in areas where perennial streams cross a Trout Creek Sandstone outcrop, and <br />land-surface elevations were used as a guide to setting these constant-head <br />elevations. A constant-head node was not placed at the head of Hubberson <br />Gulch where it crosses the sandstone outcrop because the intermittent flow in <br />Hubberson Gulch and the stream alluvium and/or Trout Creek outcrop <br />materials are probably unsaturated here. As a result, intermittent stream flows <br />will be independent of, or not affected by the drawdown induced by pumpage. <br />• <br />5 <br />