Boundary and Initial Conditions

Boundary conditions default to no-flow around the margins of the model. Given the two-orders of magnitude difference between the conductivity of layers 2 (Qal) and 3 (Kc) this is effectively a no-flow boundary as well. Initial gradients in the system were established and maintained using constant-head conditions at the NW and SE valley terminations in the model grid (diamond symbols in Fig. 13). These head values were adopted from the interpolated water-table observation data [Latta, 1948,Bermudez, 1986]. Constant-head conditions were maintained along Big Creek using the MODFLOW River Package. River bed elevations were interpolated using well collar elevations, USGS DEM data, and topographic contours digitized from USGS 7.5' maps. Conductance of the river bed was set to 0.1 $\rm\frac{m}{d}$, stage was set to 2 m. Aquifer stresses (well withdrawals) are summarized in Table 2.