Infiltrometers

Infiltrometers are used in soil science to determine the infiltration capacity of a soil. Under natural conditions, infiltrating water is in direct contact with the soil surface, but not necessarily under atmospheric pressure. There are several infiltrometers available:

• When working with ring infiltrometers, the water is directly on the soil surface. The pressure for the infiltration process at the soil surface is determined by the atmospheric pressure and the water level in the ring infiltrometer. This pressure is unnaturally high and leads to measurement results that do not reflect the natural infiltration process.
• Other infiltrometers allow the pressure on the infiltrating water and thus the pressure for infiltration to be controlled. Typically, these infiltrometers use infiltration chambers with membranes. To establish contact between the water in the chamber and the soil, a layer of fine sand is placed on the soil before the infiltration chamber is set up. In this case, the water has no direct contact with the soil surface.

The hood infiltrometer developed by UGT combines the advantages of a ring infiltrometer and a tension infiltrometer. The water under a hood is directly on the soil surface and the system is pressure-tight at negative pressure up to the air penetration point of the soil.

The hood infiltrometer is used to measure the hydraulic conductivity of soils in the near saturated zone in field tests. The instrument consists of three components

1. the water-filled hood, as a source surface for infiltration
2. the Mariotte` s water supply consisting of infiltration vessel, bubble tower and aeration tube, to regulate the effective hydraulic pressure head at the soil surface
3. the U-tube manometer, which, together with the riser tube on the hood, serves for the exact measurement of the selected hydraulic pressure head

For the hydraulic characterization of the soil from saturated to dry conditions, we recommend the combination of hood infiltrometer (measurement in the near saturated area), tension infiltrometer (measurement in the unsaturated area) and several soil tensiometers installed at shallow depths to record the effective water tension before the lower layer boundary.