Duration Of Effective Rainfall Given Time Of Peak Calculator

Formula Used:

\[ \text{Standard Duration of Effective Rainfall} = 2 \times (\text{Time of Peak} - \text{Basin Lag}) \] \[ t_r = 2 \times (T_p - t_p) \]

Standard Duration of Effective Rainfall (tr):

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1. What is the Standard Duration of Effective Rainfall?

The Standard Duration of Effective Rainfall is a hydrological parameter that represents the time period over which rainfall contributes effectively to runoff. It is calculated based on the time of peak discharge and basin lag time.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ t_r = 2 \times (T_p - t_p) \]

Where:

\( t_r \) — Standard Duration of Effective Rainfall (Hour)
\( T_p \) — Time of Peak (Hour)
\( t_p \) — Basin Lag (Hour)

Explanation: The formula calculates the effective rainfall duration by doubling the difference between the time of peak discharge and the basin lag time.

3. Importance of Duration Calculation

Details: Accurate calculation of effective rainfall duration is crucial for flood forecasting, watershed management, and hydrological modeling. It helps in understanding the rainfall-runoff relationship and predicting peak discharge times.

4. Using the Calculator

Tips: Enter Time of Peak and Basin Lag in hours. Both values must be positive numbers, with Time of Peak greater than Basin Lag for meaningful results.

5. Frequently Asked Questions (FAQ)

Q1: What is Time of Peak?
A: Time of Peak is the time interval from the start of rainfall to the peak discharge in a hydrograph.

Q2: What is Basin Lag?
A: Basin Lag is the elapsed time between the occurrences of the centroids of the effective rainfall and the resulting runoff.

Q3: Why is the duration calculated as twice the difference?
A: This formulation accounts for the symmetrical nature of the unit hydrograph and provides a standardized duration for effective rainfall analysis.

Q4: What are typical values for these parameters?
A: Values vary by watershed characteristics. Time of Peak typically ranges from 2-12 hours, while Basin Lag ranges from 1-8 hours depending on basin size and topography.

Q5: Can this formula be used for all watersheds?
A: While widely applicable, the formula may need adjustment for extremely large or small watersheds, or those with unusual hydrological characteristics.