92 Specified-Head: IBOUND < 0 No-Flow: IBOUND = 0 Variable-Head: IBOUND > 0 As stated in section 4.1, there are constant-head boundaries on the south and east sides of the model grid. These cells receive a negative IBOUND value. Along the southern border, the constant head boundary covers the full extent of the top three layers, while the extent over the eastern border is more limited (Figure 58). These cells represent all of the alluvium at the limits of the model domain. They are constant-head due to the ground-water flow entering and leaving the sub-regional aquifer to the south and east (Figure 49). Other than the entry and exit points of the Chena and Tanana Rivers, the rest of the modelâ&#x20AC;&#x2122;s boundaries consist of bedrock. These bedrock cells are set as no-flow boundaries. A no-flow boundary condition is assigned because the amount of groundwater flow entering and exiting the alluvial aquifer through bedrock is considered negligible.
N CONSTANT-HEAD BOUNDARIES
Figure 58. Illustration of constant-head boundaries (green) at southern and eastern edges of model domain. Vertical exaggeration 5X.