ABSTRACT
Figure 20.1 shows an initial model setup and the flow model results for a portion of a confined
aquifer between two equipotential boundaries, a lake and a river, which are 1000 m apart. The
aquifer uniform thickness is 30 m and the aquifer does not receive any arealy distributed
recharge, and it does not lose water to the underlying or overlying strata. The groundwater
flow in the aquifer is entirely controlled by the two surface water features, which fully
penetrate the aquifer and are in direct hydraulic connection with it. The elevation of the lake
surface is 81 m asl, and the river has uniform gradient from the south to the north; in the south,
the elevation of water surface in the river is 76 m asl, and in the north it is 71.5 m asl. For the
initial analysis, assume no-flow boundaries along the southern and northern edges of the
model domain shown in Figure 20.1. The effective porosity of the aquifer material is 25%, and
the storage coefficient is estimated to be 0.001. The hydraulic conductivity is initially estimated
at 50 m=d throughout the aquifer. There is a fully penetrating water supply well located near the river as shown in Figure 20.1. This well, when operating, is pumping 60 L=s or 5000 m3=d. Cell size of the model is 1010 m everywhere except in the far corners where the largest cell has dimension of 2020 m. After setting up and running the flow model with the above parameters and boundary conditions in steady state, analyze potential migration of a dissolved contam-
inant plume that has just started to develop from a continuous source shown in Figure 20.1 for
the next 10 y. Analyze two scenarios: when the well is not pumping and when it is pumping
continuously. For the later case, run the model in transient conditions. The constant dissolved
concentration of the contaminant in the source zone will be kept at 1000 mg=L for the entire period of 10 y. The contaminant does not sorb to the aquifer material and it does not degrade.
After analyzing the contaminant fate and transport with the assumed uniform hydraulic
conductivity in the aquifer, run the model with a varying hydraulic conductivity as shown
later in this chapter.
