1. What is Basin Lag?

Basin Lag is the elapsed time between the occurrences of the centroids of the effective rainfall. It represents the time delay between rainfall and the resulting runoff peak in a watershed.

2. How Does the Calculator Work?

The calculator uses the Snyder's formula:

Where:

• \( C_p \) — Regional Constant (Snyder), an indication of the retention and storage capacity of the watershed
• \( A \) — Area of Catchment (km²)
• \( Q_p \) — Peak Discharge (m³/s)
• 2.78 — Unit conversion constant

Explanation: This formula calculates the time lag between rainfall centroid and peak discharge in a watershed, considering the watershed's characteristics and peak flow rate.

3. Importance of Basin Lag Calculation

Details: Basin lag calculation is crucial for flood forecasting, hydraulic structure design, and watershed management. It helps in predicting flood timing and designing appropriate drainage systems.

4. Using the Calculator

Tips: Enter Regional Constant (typically ranges from 0.4 to 0.8), Area of Catchment in km², and Peak Discharge in m³/s. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for Snyder's Regional Constant?
A: Snyder's Regional Constant typically ranges from 0.4 to 0.8, depending on watershed characteristics and regional hydrology.

Q2: How does basin lag affect flood prediction?
A: Shorter basin lag indicates quicker response to rainfall, potentially leading to flash floods, while longer lag times allow for more warning time.

Q3: What factors influence basin lag?
A: Basin lag is influenced by watershed size, shape, slope, land use, soil type, and channel characteristics.

Q4: Can this formula be used for all watershed types?
A: While widely applicable, the formula may need calibration for specific regional conditions and watershed characteristics.

Q5: How accurate is the Snyder's method?
A: Snyder's method provides reasonable estimates for many watersheds but should be calibrated with local data for optimal accuracy.