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Basin Lag Formula:
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Basin Lag is the elapsed time between the occurrences of the centroids of the effective rainfall. It is an important parameter in hydrology for understanding the timing characteristics of watershed response to rainfall events.
The calculator uses the Basin Lag formula:
Where:
Explanation: This formula adjusts the modified basin lag by accounting for non-standard rainfall duration to calculate the actual basin lag time.
Details: Accurate basin lag calculation is crucial for flood forecasting, watershed management, and designing hydraulic structures. It helps in predicting the timing of peak flows and understanding watershed response characteristics.
Tips: Enter modified basin lag and non-standard rainfall duration in hours. Both values must be valid positive numbers.
Q1: What is the difference between basin lag and time of concentration?
A: Basin lag refers to the time between rainfall centroid and runoff centroid, while time of concentration is the time for water to travel from the most distant point to the watershed outlet.
Q2: How does rainfall duration affect basin lag?
A: Longer rainfall durations typically result in longer basin lag times as the watershed takes more time to respond to extended rainfall events.
Q3: What factors influence basin lag in a watershed?
A: Watershed size, shape, slope, land use, soil type, and channel characteristics all influence basin lag time.
Q4: Why is the 21/22 factor used in the formula?
A: This factor is derived from empirical studies and represents the relationship between modified basin lag and actual basin lag for standard conditions.
Q5: How accurate is this calculation method?
A: The formula provides a reasonable estimate for many watersheds, but site-specific calibration may be needed for precise applications in complex watersheds.