Infiltration - Hood Infiltrometer

Parameter to be measured:

Infiltrability, hydraulic conductivity

Method:

Tension-infiltrometer (UGT IL-2700): Measures infiltration rate within a hood that is placed onto soil surface. Hydraulic head within hood can be adjusted between 0 (=saturated conductivity) and bubbling pressure by means of a Mariotte-bottle, optional data interface and software (I haven't worked with these)

Equipment:

• main reservoir (with combined) Mariotte-bottle
• hood (various sizes), steel rim
• connecting tubes, manometer (e.g. U-style), hand pump
• datasheets, stop watch, sand (for sealing hood rim with soil surface)
• scissors for clipping vegetation
• spade (if levelling or deeper measurements are necessary)
• large water vessels for supply

Advantages:

• in-situ measurement, no analysis of disturbed soil samples in lab
• no contact layer with soil required (as with ceramic plates)
• works with reasonably uneven surfaces and original vegetation
• no need to drill neat holes (as with a constant head permeameter like the Amoozemeter) which is problematic in stony soils

Disadvantages:

• heavy, comes in huge metal suitcase (17 kg)
• large water consumption with sandy soils
• many pipes and valves - requires practice and understanding to recognise errors, set-up time
• lots of potentially leaky connections and many parts to loose in the field
• measurement in different depths of soil profile is complicated, though possible when digging pits
• price

What to watch out for:

potential problems with

• hydrophobic soils
• heterogenous water content of soil before measurement
• strong effects from preferential flowpaths
• strong swelling/shrinking of soil
• effects of impermeable layers before stationarity is achieved
• inclined, uneven surfaces
• inequivocal identification of stationary flow

(worksheet of H. Elsenbeer)

• insolation and temperature related problems

Links

UGT [1] no-frills-instruction (in German) [2]

Projects that used the above equipment: SESAM [3]

Other related web sites:

References

Gardner, W.R., 1958. Some steady-state solutions of unsaturated moisture flow equations with application to evaporation from a water table. Soil Science 85, 228-232.

Wooding, R.A., 1968. Steady infiltration from a shallow circular pond. Water Resources Research 4, 1259-1273.