1. What is Modified Basin Lag?

Modified Basin Lag is a hydrological parameter that represents the time difference between the centroid of rainfall excess and the centroid of direct runoff hydrograph for an effective duration rainfall.

2. How Does the Calculator Work?

The calculator uses the Modified Basin Lag formula:

Where:

• \( t'_p \) — Modified Basin Lag (Hour)
• \( t_b \) — Time Base (Hour)

Explanation: This formula calculates the modified basin lag by subtracting 72 from the time base and dividing the result by 3.

3. Importance of Modified Basin Lag Calculation

Details: Accurate Modified Basin Lag estimation is crucial for hydrological modeling, flood forecasting, and watershed management. It helps in understanding the timing characteristics of runoff response to rainfall events.

4. Using the Calculator

Tips: Enter Time Base in hours. The value must be valid (Time Base > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is Time Base in hydrology?
A: Time Base is the time from which the direct runoff begins until the direct-runoff ends, representing the duration of the direct runoff hydrograph.

Q2: Why subtract 72 in the formula?
A: The constant 72 represents a baseline time adjustment based on empirical studies and standard hydrological practices for this specific calculation.

Q3: What are typical values for Modified Basin Lag?
A: Values vary significantly based on watershed characteristics, but typically range from a few hours to several days depending on basin size and topography.

Q4: When is this calculation most useful?
A: This calculation is particularly useful in flood prediction, reservoir operation planning, and designing drainage systems.

Q5: Are there limitations to this formula?
A: This formula provides an approximation and may need adjustment for specific watershed conditions, extreme weather events, or unusual basin characteristics.