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The Width of Unit Hydrograph at 75% Peak Discharge (W75) is a hydrological parameter that represents the width of the unit hydrograph at 75% of the peak discharge value. It is used to characterize the shape and timing of the runoff hydrograph resulting from a given excess rainfall event.
The calculator uses the formula:
Where:
Explanation: This formula provides a simple relationship between the width at 50% peak discharge and the width at 75% peak discharge, with the latter being approximately 57.14% of the former.
Details: Calculating W75 is important for hydrological analysis and flood forecasting. It helps in characterizing the shape of the unit hydrograph, which is essential for predicting the timing and magnitude of runoff from rainfall events.
Tips: Enter the width at 50% peak discharge (W50) in meters. The value must be greater than zero. The calculator will compute the corresponding width at 75% peak discharge (W75).
Q1: What is a unit hydrograph?
A: A unit hydrograph represents the direct runoff response from a watershed to a unit depth of excess rainfall distributed uniformly over the watershed for a specified duration.
Q2: Why are different percentage widths important?
A: Different percentage widths (W50, W75) help characterize the shape of the hydrograph, which affects the timing and distribution of runoff and is crucial for flood prediction and water resource management.
Q3: How is W50 typically determined?
A: W50 is usually determined from observed hydrograph data or through regional empirical relationships based on watershed characteristics.
Q4: Are there limitations to this formula?
A: This formula provides a simplified relationship and may not be accurate for all watersheds. Local calibration and verification are recommended for specific applications.
Q5: Can this calculator be used for any unit system?
A: The calculator uses meters as the unit for both W50 and W75. If using other units, appropriate conversion is necessary before and after calculation.