Soil–water terminology: The property of earth that describes its ability to allow water to pass through it is called

Introduction / Context:
Hydrogeology and geotechnical engineering use several related but distinct terms to describe how water interacts with soil: porosity, perviousness, permeability, and transmissibility. Correctly distinguishing these is vital for seepage analyses, well design, and filter criteria.

Given Data / Assumptions:

• No special conditions; standard definitions apply.
• We seek the property directly governing water flow through a porous medium under a hydraulic gradient.

Concept / Approach:
Permeability (hydraulic conductivity, k) is the quantitative property that relates flow rate to hydraulic gradient via Darcy’s law. Porosity is the volume fraction of voids, which influences but does not alone determine flow rate because pore connectivity and size distribution matter. Perviousness is a qualitative term indicating how open a material seems to flow. Transmissibility (transmissivity, T = K * b) applies to aquifers and equals hydraulic conductivity times saturated thickness—useful for areal flow, not a point property of the soil alone.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory constant-head tests produce k; pumping tests infer T. Both reinforce that permeability is the flow-governing property at the material level.

Why Other Options Are Wrong:
Porosity alone cannot predict flow; perviousness is descriptive; transmissibility includes thickness; sorption capacity relates to chemical interactions, not bulk flow.

Common Pitfalls:
Equating high porosity with high permeability (e.g., clay has high porosity but low permeability).

Final Answer:
Permeability (hydraulic conductivity)