This presentation will provide you complete knowledge regarding measurement of infiltration by using double ring infiltrometer.

1. Measurement of Infiltration
Vijitha Vikneshwaran
Lecturer (Temporary)
Faculty of Technology
University of Jaffna

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

10. Infiltrometer
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Ground Level
Water Level
Outer Cylinder
Inner Cylinder
Point gauge
10 cm
15 cm
Schematic sketch of cylinder Infiltrometer

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…

18. Readings
Time Elapsed
time
Gauge
reading
Infiltration Infiltrati
on rate
Cumulative
infiltration
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19. Graph for infiltration and infiltration rate
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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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21. THANK YOU
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