Precipitation Given Total Runoff Depth For Practical Use Calculator

Formula Used:

\[ \text{Total Storm Precipitation} = \text{Total Direct Runoff} + (\Phi\text{-Index} \times \text{Duration of Rainfall Excess}) \] \[ P = R_d + (\varphi \times t_e) \]

Total Storm Precipitation (P):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Total Storm Precipitation Formula?

The Total Storm Precipitation formula calculates the total precipitation from a storm event by combining direct runoff with the product of Φ-Index and duration of rainfall excess. This equation is fundamental in hydrology for water balance calculations and flood prediction.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P = R_d + (\varphi \times t_e) \]

Where:

\( P \) — Total Storm Precipitation (cm)
\( R_d \) — Total Direct Runoff (cm)
\( \varphi \) — Φ-Index (cm/h)
\( t_e \) — Duration of Rainfall Excess (hours)

Explanation: The formula accounts for both the direct runoff component and the infiltration component of storm precipitation, providing a complete picture of water distribution during a storm event.

3. Importance of Precipitation Calculation

Details: Accurate precipitation calculation is crucial for hydrological modeling, flood forecasting, water resource management, and infrastructure design. It helps in understanding watershed behavior and predicting potential flood risks.

4. Using the Calculator

Tips: Enter total direct runoff in centimeters, Φ-Index in cm/h, and duration of rainfall excess in hours. All values must be non-negative numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is Φ-Index?
A: Φ-Index is the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount. It represents the average infiltration rate during a storm event.

Q2: How is duration of rainfall excess determined?
A: Duration of rainfall excess is the total time during which rainfall intensity exceeds the infiltration capacity, typically determined from rainfall hyetograph analysis.

Q3: What are typical values for these parameters?
A: Values vary by region and soil type. Direct runoff typically ranges from 0-50 cm, Φ-Index from 0.1-5 cm/h, and duration from 0.1-48 hours depending on storm characteristics.

Q4: Are there limitations to this formula?
A: The formula assumes constant infiltration rate (Φ-Index) and may not accurately represent complex storm patterns or varying soil moisture conditions.

Q5: How is this used in practical applications?
A: This calculation is used in flood prediction models, drainage system design, irrigation planning, and environmental impact assessments.