Boundary Conditions Exercise

Make a sketch (yes, I mean take out a pencil and paper) and designate the boundary conditions of the hypothetical ground-water systems represented by the following well-known formulas:

1a. Theis non-equilibrium formula: The assumptions of this formula are listed in many books; careful consideration should reveal that several of these "assumptions" in fact describe the boundary conditions of the hypothetical ground-water system.

1b. Dupuit formula for radial flow under water-table conditions:

1c. Thiem equation for flow to a well in a confined aquifer written in terms of head (h):

Consider the various possible relationships between these "model" boundary conditions and the boundary conditions in field situations.

Make a sketch in plan view and in cross section of the following types of groundwater systems and designate appropriate boundary conditions. Each system may be represented in several different ways, but most ground-water hydrologists will probably treat some boundary conditions in these systems in the same way.

2a. An oceanic island in a humid climate; permeable materials are underlain by relatively impermeable bedrock;

2b. An alluvial aquifer associated with a medium-sized river in a humid climate; the aquifer is underlain and bounded laterally by bedrock of low hydraulic conductivity;

2c. An alluvial aquifer associated with an intermittent stream in an arid climate; the aquifer is underlain and bounded laterally by bedrock of low to intermediate hydraulic conductivity;

2d. A western valley with internal drainage in an arid region; intermittent streams flow from surrounding mountains towards a valley floor; a part of valley floor is playa;

2e. A confined aquifer bounded above and below by leaky confining beds.

View the answer key to evaluate you work.

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