Water Quality Volume Calculator
Estimate the runoff volume that must be captured or treated for a selected water quality design storm.
Water quality volume is based on drainage area, design rainfall depth, and runoff coefficient.
Water Quality Volume Calculator
Estimate runoff volume for treatment sizing.
Confirm the required design storm and sizing method with the local stormwater manual.
What this calculator does
This calculator estimates the runoff volume for stormwater treatment sizing using contributing area, rainfall depth, and runoff coefficient.
Inputs explained
- Drainage area: Contributing area draining to the BMP or treatment point.
- Design rainfall depth: Required water quality storm depth from the local stormwater manual.
- Runoff coefficient: Factor used to represent imperviousness and runoff response.
Limitations
Stormwater manuals may require retention, treatment, drawdown checks, routing, or specific BMP sizing methods. Confirm local criteria before design use.
FAQ
What is water quality volume?
It is the runoff volume that a BMP may need to capture, treat, infiltrate, reuse, or detain for water quality compliance.
Is this the same as detention volume?
No. Water quality volume is usually focused on treatment or retention. Detention volume is usually focused on flow control.
Where do I get the design rainfall depth?
Use the rainfall depth required by the local stormwater manual, project permit, or BMP design guidance.
Related tools
Need help reviewing this result?
Use this calculator for planning-level checks, then request help if you need a second look at assumptions, units, stormwater criteria, pump sizing, storage volume, or report-ready calculations.