View source for Infiltration - Hood Infiltrometer

[[Image: Hood_infiltometer.png |right|300px|]]
==Parameter to be measured:==
Infiltration capacity, unsaturated hydraulic conductivity, bubble pressure point

==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. Newer versions provide a pressure sensor and data interface. The "logger" device comes in two versions: Rev1 the "logger" can only monitor the water table, Rev2 the logger really logs the water level in the reservoir and stores all experiments.
[[Image: Hood infiltrometer.png |right|300px|]]

==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) (some wire straps may help connecting the many bits and pieces to a portable pack)
* 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 (bring silicone grease)
* at some locations it is difficult to get a suction head established as air enters the hood through macropores or root channels
* 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
* in case of high macroporosity , use a metal ring with a larger depth to prefent the effect on the measurment than seal the hood with too much sand, because measurement area will in that case be error prone

==Problems/Questions:==


==Links==

[http://ugt-online.de/en/produkte/bodenkunde/messgeraete-fuer-die-hydraulische-und-pneumatische-leitfaehigkeit/haubeninfiltrometer-il-2700.html UGT]

[http://brandenburg.geoecology.uni-potsdam.de/projekte/sesam/download/fieldwork/haube_fuer_dummys.pdf no-frills-instruction (in German)]

Projects that used the above equipment:

* [http://brandenburg.geoecology.uni-potsdam.de/projekte/sesam/index.php SESAM]
* [http://www.comtess.uni-oldenburg.de/ COMTESS]
* [http://www.grosshang.de/index.php/naturalslope.html Natural Slope]
* [http://www.caos-project.de/index.php CAOS]

Other related web sites:

[http://www.usyd.edu.au/su/agric/acpa/people/budi/punzel/hood.htm Punzelmeter at the University of Sydney]

==References==
*Bens, O., Wahl, N.A., Fischer, H., Hüttel, R.F. 2007. Water infiltration and hydraulic conductivity in sandy cambisols: impacts of forest transformation on soil hydrological properties. Eur J Forest Res 126,101–109, DOI 10.1007/s10342-006-0133-7.
*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.
*Schwaerzel, K., Punzel, J., 2007. Hood infiltrometer - A new type of tension infiltrometer. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL  71(5), 1438-1447, DOI: 10.2136/sssaj2006.0104.
*Wooding, R.A., 1968. Steady infiltration from a shallow circular pond. Water Resources Research 4, 1259-1273.




[[Category:Equipment]]
[[Category:Infiltration]]