Hydraulic conductivity tells how easily water moves through soil or rock – gravel drains quickly, clay barely at all. It is needed for well design, drainage, landfills and dam seepage.
How to use the Hydraulic Conductivity Calculator
- Method
- Effective grain size d₁₀
- Hazen coefficient C
- Porosity n
- Flow rate
- Sample length L
- Sample area A
- Head difference h
- Standpipe area a
- Initial head h₁
- Final head h₂
- Elapsed time t
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the method and enter the values.
Inputs explained
| Field | What to enter |
|---|---|
| Method | Choose one: Hazen (grain size), Kozeny–Carman (grain size & porosity), Constant-head test, Falling-head test |
| Effective grain size d₁₀ | Units: mm, cm, m, in, µm |
| Hazen coefficient C | A number |
| Porosity n | A number |
| Flow rate | Units: mL/s, L/s, L/min |
| Sample length L | Units: cm, mm, m, in, ft |
| Sample area A | Units: cm², m² |
| Head difference h | Units: cm, mm, m, in, ft |
| Standpipe area a | Units: cm², mm² |
| Initial head h₁ | Units: cm, mm, m, in, ft |
| Final head h₂ | Units: cm, mm, m, in, ft |
| Elapsed time t | Units: s, ms, min, h, days |
Example values
How the main result changes when Effective grain size d₁₀ changes and everything else stays at the example values above:
| Effective grain size d₁₀ (mm) | Hydraulic conductivity K (cm/s) |
|---|---|
| 0.1 | 0.01 |
| 0.15 | 0.0225 |
| 0.2 | 0.04 |
| 0.25 | 0.0625 |
| 0.3 | 0.09 |
| 0.4 | 0.16 |
Formula
Hazen: K (cm/s) = C·d₁₀² (cm) · Kozeny–Carman: K = (ρg/μ)·n³/(1 − n)²·d₁₀²/180
Constant head: K = Q·L/(A·h) · Falling head: K = (a·L/(A·t))·ln(h₁/h₂)
Worked example
Inputs — Method: Hazen (grain size); Effective grain size d₁₀: 0.2 mm; Hazen coefficient C: 100.
Results — Hydraulic conductivity K = 0.04 cm/s; Intrinsic permeability (water, 20 °C) = 41.48643 darcy; Typical of = Clean sand.
Key terms
- Hydraulic conductivity
- Darcy flux per unit hydraulic gradient.
Frequently asked questions
What is d₁₀?
The grain size than which 10% of the soil (by mass) is finer.
When is Hazen's formula valid?
For clean sands with d₁₀ between 0.1 and 3 mm.
Which lab test should I use?
Constant head for sands and gravels; falling head for finer soils.
How does K relate to permeability?
K = k·ρg/μ – it also depends on the fluid.