1. What is Time of Recession?

Time of Recession represents the withdrawal of water from the storage built up in the basin during the earlier phases of the hydrograph. It is an important parameter in hydrological analysis and flood prediction.

2. How Does the Calculator Work?

The calculator uses the SCS suggested formula:

Where:

• \( T_c \) — Time of Recession (Seconds)
• \( T_p \) — Time of Peak (Seconds)

Explanation: This formula provides a simplified method to estimate the recession time based on the time to peak discharge, as suggested by the Soil Conservation Service (SCS).

3. Importance of Time of Recession Calculation

Details: Accurate estimation of recession time is crucial for flood forecasting, reservoir operation, and watershed management. It helps in understanding the basin's response to rainfall events and predicting the duration of high water levels.

4. Using the Calculator

Tips: Enter Time of Peak in seconds. The value must be valid (greater than 0). The calculator will compute the corresponding Time of Recession using the SCS suggested coefficient of 1.67.

5. Frequently Asked Questions (FAQ)

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

Q2: Why is the coefficient 1.67 used in this formula?
A: The coefficient 1.67 is empirically derived by the Soil Conservation Service (SCS) based on extensive hydrological studies and represents the typical ratio between recession time and time to peak.

Q3: Are there limitations to this formula?
A: This formula provides a general estimation and may need adjustment for specific basin characteristics, land use patterns, or extreme hydrological events.

Q4: Can this formula be used for all types of watersheds?
A: While widely applicable, the formula works best for small to medium-sized watersheds with typical SCS curve numbers. Large or complex watersheds may require more detailed analysis.

Q5: How accurate is this estimation method?
A: The method provides a reasonable first approximation but should be validated with observed data for specific watershed applications where precision is critical.