Subcatchment Runoff

🔍 Summary of the Difference

Item	subcatchment.statistics.get("runoff")	subcatchment.runoff
Meaning	Cumulative runoff statistics over the entire simulation period	Instantaneous runoff at the current time step
Units	Usually total volume (m³ or ft³)	Instantaneous flow rate (e.g., CMS, CFS)
When to Use	After simulation ends	During simulation step-by-step
Purpose	Summary/analysis (e.g., compare total runoff)	Real-time control/logging (e.g., LID response monitoring)

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🔹 subcatchment.statistics.get("runoff")

• subcatchment.statistics is available after the simulation finishes.
• .get("runoff") returns the total volume of runoff generated from the subcatchment.

🧾 Example:

print(subcatchment.statistics.get("runoff"))  # 12345.67 (m³)

📌 Tip: .get() can also take keys like "infiltration", "evaporation", "precipitation", etc.

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🔹 subcatchment.runoff

• This provides the instantaneous runoff rate during a simulation step.
• The unit depends on the model's unit system (e.g., CMS or CFS).

🧾 Example:

for step in sim:
    print(subcatchment.runoff)  # 0.015 (cms)

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💡 Real-Life Analogy

Item	Analogy
subcatchment.runoff	The flow of water coming out at this very moment (e.g., L/sec)
subcatchment.statistics.get("runoff")	The total amount of water that came out after the rain event ends

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🎯 Summary Code Example

# Instantaneous runoff (during simulation)
print("runoff: ", subcatchment.runoff)

# Cumulative runoff (after simulation ends)
print("statistics_runoff: ", subcatchment.statistics.get("runoff"))