Variables
Description
What is this formula?
The Hazen-Williams flow rate equation estimates water flow in pressurized pipes using pipe diameter, hydraulic slope, and a roughness coefficient.
When to use it
Use this formula for irrigation pipelines, agricultural water distribution systems, and pressurized water networks where the fluid is water under normal temperature conditions.
Example
A farm irrigation pipe has:
C = 140
D = 0.10 m
S = 0.015
Formula:
Q = 0.278·C·D^2.63·S^0.54
Substitution:
Q = 0.278 × 140 × 0.10^2.63 × 0.015^0.54
Q = 0.0080 m³/s
Result:
The estimated flow rate is approximately 0.0080 m³/s, or 8.0 L/s.
Applications
- Irrigation pipeline sizing
- Agricultural water distribution
- Sprinkler irrigation systems
- Drip irrigation mainlines
- Pressurized pipe flow estimation
Note
The Hazen-Williams equation is an empirical approximation mainly valid for water flow in pressurized pipes. It is widely used in irrigation and water supply design, but it is not a universal fluid mechanics law and should not be applied to fluids with very different viscosity or extreme temperature conditions.