---
title: "Permeability versus hydraulic conductivity"
subject: "Engineering Geology I"
chapter: 6
key: "semester_3/engineering_geology_i:permeability-versus-hydraulic-conductivity"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/permeability-versus-hydraulic-conductivity
site: BCT Engineering
---

# Permeability versus hydraulic conductivity

Engineering Geology I · Chapter 6: Physical Geology

- Asked in: 2063 Baisakh (old course), 2 marks
- Video: [34 Hydraulic conductivity and intrinsic permeability](https://www.youtube.com/watch?v=rzggeQpZjLI) — GEOG 311
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/permeability-versus-hydraulic-conductivity
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-6

## Question

Differentiate between permeability and hydraulic conductivity.

## Short answer

Permeability (intrinsic, k) is a property of the porous medium alone (units m² or darcy), independent of fluid. Hydraulic conductivity (K) depends on both medium and fluid, with K = kρg/μ and units m/s. Groundwater flow uses K; petroleum uses k.

## Answer

**Permeability** (intrinsic permeability, $k$) is a property of the porous medium alone, independent of the fluid. **Hydraulic conductivity** ($K$) depends on both the medium and the fluid (its density and viscosity).

$$
K = \frac{k\,\rho\,g}{\mu}
$$

| Point | Permeability ($k$) | Hydraulic conductivity ($K$) |
|---|---|---|
| Depends on | Pore size and shape only | Medium and fluid (density, viscosity) |
| Unit | m$^2$ or darcy | m/s |
| Fluid | Same for all fluids | Different for water, oil, etc.; changes with temperature |
| Use | Oil and gas, general | Groundwater, Darcy's law $Q = KiA$ |

In many civil engineering books the term "coefficient of permeability" is used for $K$ in m/s.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Intrinsic permeability depends on:
   A. Both medium and fluid
   B. Fluid viscosity only
   C. The porous medium only, not the fluid
   D. Temperature only
   Answer: C. Hydraulic conductivity depends on both. (Key point: Dependence)

2. Hydraulic conductivity is related to permeability by:
   A. K = k mu / (rho g)
   B. K = k + rho g
   C. K = k / rho
   D. K = k rho g / mu
   Answer: D. Density and viscosity of the fluid enter K. (Key point: Formula)

3. Units of permeability and hydraulic conductivity respectively are:
   A. m^2 (or darcy) and m/s
   B. m/s and m^2
   C. kg and N
   D. Pa and m
   Answer: A. K is a velocity-type quantity used in Darcy's law Q = KiA. (Key point: Units)

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