2. Introduction
• Infiltration is the vertical movement of water into the soil
at the surface and its subsequent movement downward
in the soil.
• The double ring infiltrometer is used to measure the
infiltration.
• This is important to evaluate the soil properties for
agricultural potential.
• The principle of the method is to observe the fall of
water level in the inner of two cylinders driven
concentrically into the soil surface.
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3. • The outer ring minimizes the error due to flow
divergence other than vertical.
• The measurements can be carried out on the top soil as
well as on each of the subsoil horizon and sub stratum.
• Infiltration characteristic of soils provide useful
information on,
• Acceptance of rainfall into soil
• Water logging of land
• Erosion hazards
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Introduction,cont…
4. • Knowledge of this infiltration is necessary for efficient
management of,
• Irrigation
• Drainage
• Flood
• Soil erosion
• This process is affected by
• Surface runoff
• Soil porosity
• Initial moisture content
• Vegetative cover
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Introduction,cont…
5. • An infiltration rate is generally high during the initial
stages and reduces to a constant value with time.
• Infiltration should be continued at least four hours even
if the readings indicate that the constant rate has been
reached earlier.
• Infiltration rate is the rate at which infiltration takes
place.
• It is expressed in depth of water per unit of time, usually
in mm per hour.
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Introduction,cont…
6. • The double-ring infiltrometer is often used to measure
infiltration rates.
• There are two operational techniques used with the
double-ring infiltrometer for directly measuring soil
infiltration rates.
• Constant head method
• Falling head method
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Introduction,cont…
7. Constant head and falling head method
Constant head method
• In this method, the water level in the inner ring is
maintained at a fixed level and the volume of water used
to maintain this level is measured.
Falling head method
• In this method, the time that the water level takes to
decrease in the inner ring is measured.
• In both constant head and falling head tests, the water
level in the outer ring is maintained at a constant level to
prevent leakage between rings and to force vertical
infiltration from the inner ring.
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8. Principle
• The rate of infiltration is determined by the amount of
water that infiltrates into the soils per surface area, per
unit time.
• Infiltration can be measured by either a single or double
ring Infiltrometer, with preference usually lying with the
double ring.
• Because the outer ring helps in reducing the error that
may result from lateral flow in the soil.
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9. 9
Needed apparatus
Double ring infiltrometer
Stop watch
Float
Hammer
Pull out hooks
Measuring bridge
Measuring rod
Driving plate
11. • An Infiltrometer consists of two concentric cylinders of
25 cm height and made of 2 mm thick rolled steel.
• The diameter of inner and outer cylinder is 30 cm and 60
cm respectively.
• The inside cylinder is used to measure the infiltration
rate
• The outer one is a guard cylinder for ponding water in
the buffer area around the inner cylinder.
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Infiltrometer,cont…
12. Methodology
• Select suitable site for the experiment.
• Avoid sites near or on foot paths, close to base of trees,
near or on old termite mounds, or visible cracks or insect
hole should be avoided.
• Clip the vegetation and remove loose material which
would float.
• Insert the cylinder 10 cm depth into the soil.
• The penetration of the cylinder into the soil must be
uniform and vertical.
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13. • To achieve this draw a line along the outer circumference
of the cylinder parallel to and above cutting edge to
which the cylinders are to be driven into the soil.
• Install the device by driving them in to the soil with
falling weight type hammer.
• Rotate the direction of the hammer blows and observe
the distance between the soil surface and circular line
around the cylinder to ensure uniform penetration.
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Methodology,cont…
14. • The area enclosed around the cylinder has chance to get
crack while inserting the cylinder into the soil which
influence the infiltration.
• If the distance between soil and cylinder is more than 2 mm,
the reinstallation should be done.
• Place a wooden plank on the cylinders while hammering.
• So that the hammer does not damage the brim of the
cylinders.
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Methodology,cont…
15. • Set a hook gauge in the inner cylinder to the desired level
to which the cylinder is to be filled with water.
• Place a plastic sheet on the bottom of the inner cylinder
to dissipate the force of water and reduce turbidity and
dispersion of soil while filling the cylinders with water.
• Fill the outer cylinder to a depth of 8 – 12 cm.
• Then carefully but quickly fill the inner cylinder
• Quickly remove the plastic taking care not to disperse the
soil in the process.
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Methodology,cont…
16. • By using stop watch, note the time for the movement
water and measure the drop in water height.
• It gives an infiltration of water over time.
• If the water level becomes too low, refill the inner
cylinder.
• Use the hand or float or small plastic sheet to break the
force of water.
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Methodology,cont…
17. • Water the outer cylinder should be kept at approximately
the same level as the inner ring.
• But should not exceed the level of outer ring.
• Plot the accumulated infiltration (cm), infiltration rate
(cm/hr) in y axis and time in x axis.
• Plot the data points in a graph of cumulative infiltration
(cm) against elapsed time (min) in logarithm
• Measurement should be replicated at least three times in
each site to reduce the variability.
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Methodology,cont…
20. Data computation
• The cumulative infiltration is denoted as F.
• It is defined as the total volume of water that has infiltrated
through a unit horizontal area of soil surface over a given
period of time measured from the beginning of infiltration.
• The F can be expressed as a function of time (t)
F= atn
• Where a and n are constants for a given soil at a given
moisture content
Log F = Log a + n Log t
• The values a and n can be estimated from the graph.
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