Stream Discharge Formula
Calculate the volume of water flowing in a river or stream per unit time.
Used in hydrology and water management.
The Formula
Q = A × v
Stream discharge measures the volume of water flowing past a point per unit time. It is the product of the stream's cross-sectional area and the average water velocity.
Variables
| Symbol | Meaning |
|---|---|
| Q | Discharge (m³/s or cubic feet per second) |
| A | Cross-sectional area of the stream (m² or ft²) |
| v | Average water velocity (m/s or ft/s) |
Example 1
A stream is 4 m wide, 1.5 m deep on average, with velocity 0.8 m/s
A = 4 × 1.5 = 6 m²
Q = 6 × 0.8
Q = 4.8 m³/s (4,800 liters per second)
Example 2
A river channel is 20 ft wide, 3 ft deep, flowing at 2 ft/s
A = 20 × 3 = 60 ft²
Q = 60 × 2
Q = 120 ft³/s (cubic feet per second, or "cfs")
When to Use It
Use the stream discharge formula when:
- Monitoring river flow for flood forecasting
- Assessing water availability for agriculture or cities
- Studying watershed hydrology and erosion
- Designing bridges, dams, or irrigation systems