presentation finals

8/7/2019 presentation finals

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y Is the process by which water on the groundsurface enters the soil.

y

It is governed by two forces : gravity andcapillary action.


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y Infiltration rate (in/hr or mm/hr) is a measure ofthe rate at which soil is able to absorbrainfall or irrigation. It can be measured by

an infiltrometer.y The infiltration rateis affected by ease of entry,

storage capacity and transmission ratethrough the soil. The soil texture andstructure, moisture content, temperature,type of vegetation and rainfall all play a rolein controlling infiltration rate and capacity.


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Single Ring

Infiltrometer


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Double Ring

Infiltrometer


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General Hydrologic Budget :

Where:

F is infiltration, which can be measured as a volume or length;Is the boundary input, which is essentially the output watershed from

adjacent, directly connected impervious areas;

is the boundary output, which is also related to surface runoff,R,depending on where one chooses to define the exit point or points for the

boundary output;

P is precipitation;E is evaporation;

ET is evapotranspiration;S is the storage through either retention or detention areas;

Is the initial abstraction, which is the short term surface storage such as

puddles or even possibly detention ponds depending on size;R is surface runoff


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y Kostiakovs Equation:

Where and are empirical parameters.

The major limitation of this expression is its reliance on the zero final intake rates.

In most cases the infilration rate instead approaches a finite steady value, which in

some cases may occur after short periods of time. The Kostiakov-Lewis variant,

also known as the "Modified Kostiakov" equation corrects for this by adding a

steady intake term to the original equation.

in integrated form the cumulative volume is expressed as:

Where

Approximates, but does not necessarily equate to the final infiltration rate of

the soil.


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y Darcys Law:

This method used for infiltration is using a simplified

version of Darcys Law. In this model the ponded

water is assumed to be equal to and the head of dry

soil that exists below the depth of the wetting frontsoil suction head is assumed to be equal to .

whereis the depth of ponded water above the ground

surface;

is the hydraulic conductivity;

L is the total depth of subsurface ground in question.


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y Is the movement of water through the soil,and its layers, by gravity and capillaryforces.

y Percolation occurs under the root zone.Ground water percolates through the soilmuch as water fills a sponge, and moves

from space to space along fractures in rock,through sand and gravel, or throughchannels in formations such as cavernous

limestone


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Infiltrationand

Percolation


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y Percolation rate through soil depends on severalfactors, including the amount of water applied orinfiltrating; the adsorptive capacity of the soil; amount

of organic matter in the soil; water solubility of thesubstances mmmmmencountered; and permeabilityof the soil.


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Amarille, Jannus Victor A.

Ceniza, Orville S.

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presentation finals