The hood infiltrometer developed by UGT is used to measure the hydraulic conductivity of soils in the near-saturated zone in field tests (SCHWÄRZEL & PUNZEL 2007). The instrument consists of three components: 1) hood, 2) Mariotte` s water supply consisting of infiltration vessel, bubble tower and aeration tube and 3) U-tube manometer.

Mode of operation

Infiltration is performed from a closed hood (open at the bottom) placed on the bottom and filled with water. The circular ground surface under the hood, covered by water, forms the source surface for the infiltration flow. No additional contact layer or preparation of the soil surface is required on the measuring surface. This not only saves working time, but also allows the infiltration or hydraulic conductivity to be determined non-destructively under completely natural conditions.
The pressure under the hood is controlled by a Mariotte` s water supply. The effective hydraulic pressure head at the soil surface can be freely selected between zero and a negative pressure up to the air penetration point of the soil. The hydraulic pressure head is precisely indicated via a U-tube manometer. The hydraulic conductivity is calculated from the steady-state flow rates determined in the test run according to WOODING (1968).

Variants

In the case of the IL 2700 hood infiltrometer, the flow rate measurement data are recorded electronically with a pressure sensor in combination with the IL 2700 handheld unit and transferred to the PC and evaluated with the associated software. As a cost-effective and robust alternative even under adverse measuring conditions, the hood infiltrometer is also available without electronic data acquisition.

Two hoods with a ratio of infiltration areas of about 1:2 are available to ensure optimum adaptation of the test to the infiltration conditions present. This allows the infiltration tests to be carried out not only at different hydraulic pressure heads, but also at the same hydraulic pressure head with different infiltration areas.

Conversion to a tension infiltrometer

The hood infiltrometer functions up to the air penetration point of the soil. After that, it can be easily converted into a tension infiltrometer with our optionally available tension chamber, which allows infiltration tests up to a water tension of about 60 hPa, independent of the air penetration point of the soil.

References

SCHWÄRZEL, K. & J. PUNZEL (2007): Hood infiltrometer: New type of tension infiltrometer. Soil Sci. Soc. Am. J. 71: 1438-1447.

WOODING, R. A. (1968): Steady infiltration from a shallow circular pond. IN: Water Resources Research 4: 1259-1273.