Slug tests are particularly useful for assessing which subsurface property in a localized area?

• A. Permeability
• B. Porosity
• C. Storage coefficient
• D. Infiltration rate

Answer: (A)

Slug tests reveal how readily groundwater can move through the formation near a well. By suddenly adding or removing water and watching how the water level in the well returns to equilibrium, you’re measuring the rate at which water can flow through the pore spaces and fractures around the well—the hydraulic conductivity, which is what permeability describes in this context. This test is localized because the response is dominated by the conditions in a relatively small zone around the well, not the entire aquifer.

Porosity tells you how much water the rock can hold, not how fast water can move, so it isn’t the primary property assessed by a slug test. The storage coefficient relates to how much water the aquifer as a whole can store or release during pressure changes, which is not the main focus of slug tests. Infiltration rate concerns surface water entering the subsurface, rather than the in-situ flow property measured by slug tests.