Summer Initiative – Part IV: Hood-Infiltrometer

The hood infiltrometer is used to measure the hydraulic conductivity of soils in virtually saturated areas as field tests. The infiltration is made from a sealed hood placed on the soil and filled with water. The circular soil surface covered by water beneath the hood forms the source area for the infiltration flux. No additional contact layer and no preparation
of the soil surface is necessary on the measurement area. This not only saves working time but also makes it possible to measure the infiltration and conductivity under completely natural conditions in a destruction-free manner.
The pressure beneath the hood is
controlled using a Marriott’s water supply. The effective increase in pressure on the soil surface can be freely selected between zero and a vacuum up to the bubble point of the soil. This pressure level is shown exactly on a U-tube manometer. The hydraulic  conductivity is calculated from the stationary flux rates determined in the test run
according to WOODING (1968). With the IL-2700 the measurement data for the flux rate is
electronically recorded with a pressure sensor combined with a handheld instrument IL-2700.

With the corresponding software they are transferred to the PC and analysed.The hood infiltrometer is also available without electronic data recording as a favourably priced
alternative which is tough enough to withstand adverse measurement conditions.
In order to guarantee an optimum adjustment of the experiment to the prevailing infiltration conditions, two hoods are available with a ratio to infiltration areas of around 1:2.
The tension chamber, which is an available option, creates a tension infiltrometer
together with the Mariott’s water supply which permits infiltration experiments up to a water tension of around 60 hPa irrespective of the bubble point of the soil. For maximum protection and simple handling during transportation and storage, the complete system is packed in an aluminium framed case with carry grip and foam inlays.
Technical data
• Tension area: 0 … bubble point with hood
0 … 60 hPa with tension chamber
• Tension measurement: U-tube manometer
Resolution 0.1 hPa
• Infiltration measurement: Differential pressure sensor
0 – 70 mba
Resolution 1 mm water column
• Conductivity range of the soil: 10-3 m/s bis 10-7 m/s
The following table shows the comparison between sveral different systems available on the market:
Hoodinfiltrometer vs competetiv systems