📊 Meaning of Each Column
In the .rpt file, "Total Runoff (mm)" and "Total Runoff (10⁶ L)" represent the same runoff data but in different units.
| Column Name | Meaning |
|---|---|
| Total Runoff (mm) | Runoff depth per unit area in millimeters |
| Total Runoff (10⁶ L) | Total runoff volume in millions of liters |
📐 Key Concept Behind the Difference
mm: Describes runoff as a depth spread over the catchment area (like rainfall depth)10⁶ L: Describes runoff as a total volume
[ = Runoff (mm) × Area (m²) ÷ 1,000,000 ]
✅ Example Calculation
For Subcatchment 1:
- Total Runoff (mm) = 1.34 mm
- Total Runoff (10⁶ L) = 0.13 (i.e., 130,000 L)
You can use these to estimate the area:
runoff_mm = 1.34 # mm
runoff_liters = 0.13 * 1_000_000 # 130,000 L
# Estimate area (m²)
area = (runoff_liters / runoff_mm) * 1_000
# area ≈ 97,014.93 m²So the catchment area is approximately 0.097 km².
🔁 Unit Conversion Formulas
1. mm → Liters
[
\text{Liters} = \text{Runoff (mm)} \times \text{Area (m²)} \div 1000
]
2. Liters → mm
[
\text{Runoff (mm)} = \text{Liters} \times 1000 \div \text{Area (m²)}
]
🧠 Summary
| Item | Total Runoff (mm) | Total Runoff (10⁶ L) |
|---|---|---|
| Unit Type | Depth over area | Absolute volume |
| Interpretation | Water spread as 1.34 mm across the catchment | Total volume of water runoff |
| Needs for Conversion | Requires catchment area | Requires catchment area |
