Saturated Flow:Modeling Two-dimensional, Saturated, Lateral Groundwater Flow
Two-dimensional, saturated, lateral groundwater movement may be simulated in GSSHA. The purpose of simulating 2-D, lateral groundwater movement is to provide the effects of saturated groundwater on surface water processes, such as influences on soil moisture, infiltration, and ET, location of saturated source areas and seeps, and stream/groundwater interactions. The saturated groundwater modeling option is intended to be used in conjunction with Richards’ equation modeling of the unsaturated zone. When 2-D saturated groundwater is coupled to the Richards’ equation, the 1-D unsaturated model sits on top of the moving water table, which becomes the lower boundary condition for the unsaturated zone solver (Figure 21). The unsaturated model provides recharge (positive or negative) to the unsaturated zone.
When conducting long-term simulations (Chapter 10), it is also possible to use the GAR model of infiltration to provide estimates of groundwater recharge for the 2-D lateral groundwater solution. However, this option does not provide many of the advantages of coupling Richards’ equation to the 2-D lateral groundwater model, such as the effect of groundwater on soil moistures in the unsaturated zone. This approach is intended for simple problems and where a more qualitative result is acceptable, and has been applied as such. Downer et al. (2002b).