Phi Index for Practical Use Calculator

✖Intensity of Rainfall is the ratio of the total amount of rain (rainfall depth) falling during a given period to the duration of the period.ⓘ Intensity of Rainfall [I]			+10% -10%
✖Runoff in Cm from 24h Rainfall of intensity in centimeters per hour (cm/hr).ⓘ Runoff in Cm from 24h Rainfall [R_24-h]			+10% -10%

✖Φ-Index of a catchment is the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount.ⓘ Phi Index for Practical Use [φ]

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Formula

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Phi Index for Practical Use

Formula

`"φ" = ("I"-"R"_{"24-h"})/24`

Example

`"0.027917"=("0.8cm/h"-"0.13cm")/24`

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Phi Index for Practical Use Solution

STEP 0: Pre-Calculation Summary

Formula Used

Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24
φ = (I-R_24-h)/24
This formula uses 3 Variables

Variables Used

Φ-Index - Φ-Index of a catchment is the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount.
Intensity of Rainfall - (Measured in Centimeter per Hour) - Intensity of Rainfall is the ratio of the total amount of rain (rainfall depth) falling during a given period to the duration of the period.
Runoff in Cm from 24h Rainfall - (Measured in Centimeter) - Runoff in Cm from 24h Rainfall of intensity in centimeters per hour (cm/hr).

STEP 1: Convert Input(s) to Base Unit

Intensity of Rainfall: 0.8 Centimeter per Hour --> 0.8 Centimeter per Hour No Conversion Required
Runoff in Cm from 24h Rainfall: 0.13 Centimeter --> 0.13 Centimeter No Conversion Required

STEP 2: Evaluate Formula

Substituting Input Values in Formula

φ = (I-R_24-h)/24 --> (0.8-0.13)/24

Evaluating ... ...

φ = 0.0279166666666667

STEP 3: Convert Result to Output's Unit

0.0279166666666667 --> No Conversion Required

FINAL ANSWER

0.0279166666666667 ≈ 0.027917 <-- Φ-Index

(Calculation completed in 00.004 seconds)

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Home » Engineering » Civil » Engineering Hydrology » Abstractions from Precipitation » Infiltration Indices » Φ-Index » Phi Index for Practical Use

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Created by Mithila Muthamma PA

Coorg Institute of Technology (CIT), Coorg

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Indian Institute of Information Technology (IIIT), Bhopal

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< 11 Φ-Index Calculators

Precipitation given Total Runoff Depth for Practical Use

Go Total Storm Precipitation = Total Direct Runoff+(Φ-Index*Duration of Rainfall Excess)

Duration of Rainfall Excess given Total Runoff Depth

Go Duration of Rainfall Excess = (Total Storm Precipitation-Total Direct Runoff)/Φ-Index

Phi Index given Total Runoff Depth

Go Φ-Index = (Total Storm Precipitation-Total Direct Runoff)/Duration of Rainfall Excess

Total Direct Runoff Depth

Go Total Direct Runoff = Total Storm Precipitation-(Φ-Index*Duration of Rainfall Excess)

Runoff to Determine Phi Index for Practical Use

Go Runoff in Cm from 24h Rainfall = Coefficient Depending on Soil Type*Intensity of Rainfall^1.2

Rainfall Intensity for Phi Index of Practical Use

Go Intensity of Rainfall = (Φ-Index*24)+Runoff in Cm from 24h Rainfall

Runoff for Phi Index for Practical Use

Go Runoff in Cm from 24h Rainfall = Intensity of Rainfall-(Φ-Index*24)

Phi Index for Practical Use

Go Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24

Pulses of Time Interval from Rainfall Hyetograph

Go Pulses of Time Interval = Duration/Time Interval

Duration of Rainfall from Rainfall Hyetograph

Go Duration = Pulses of Time Interval*Time Interval

Time Interval of Rainfall Hyetograph

Go Time Interval = Duration/Pulses of Time Interval

Phi Index for Practical Use Formula

Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24
φ = (I-R_24-h)/24

What is φ-Index?

The φ index of a catchment is defined as the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount. In principle, the magnitude of the φ index is bounded between the maximum and minimum average infiltration capacities of the catchment during a rainfall event.

How to Calculate Phi Index for Practical Use?

Phi Index for Practical Use calculator uses Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24 to calculate the Φ-Index, The Phi Index for Practical Use formula is defined as the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount. Φ-Index is denoted by φ symbol.

How to calculate Phi Index for Practical Use using this online calculator? To use this online calculator for Phi Index for Practical Use, enter Intensity of Rainfall (I) & Runoff in Cm from 24h Rainfall (R_24-h) and hit the calculate button. Here is how the Phi Index for Practical Use calculation can be explained with given input values -> 0.027917 = (2.22222222222222E-06-0.0013)/24.

FAQ

What is Phi Index for Practical Use?

The Phi Index for Practical Use formula is defined as the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount and is represented as φ = (I-R_24-h)/24 or Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24. Intensity of Rainfall is the ratio of the total amount of rain (rainfall depth) falling during a given period to the duration of the period & Runoff in Cm from 24h Rainfall of intensity in centimeters per hour (cm/hr).

How to calculate Phi Index for Practical Use?

The Phi Index for Practical Use formula is defined as the constant infiltration capacity that would yield the actual total runoff for a given rainfall amount is calculated using Φ-Index = (Intensity of Rainfall-Runoff in Cm from 24h Rainfall)/24. To calculate Phi Index for Practical Use, you need Intensity of Rainfall (I) & Runoff in Cm from 24h Rainfall (R_24-h). With our tool, you need to enter the respective value for Intensity of Rainfall & Runoff in Cm from 24h Rainfall and hit the calculate button. You can also select the units (if any) for Input(s) and the Output as well.

How many ways are there to calculate Φ-Index?

In this formula, Φ-Index uses Intensity of Rainfall & Runoff in Cm from 24h Rainfall. We can use 1 other way(s) to calculate the same, which is/are as follows -

Φ-Index = (Total Storm Precipitation-Total Direct Runoff)/Duration of Rainfall Excess

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