HYPROP© - Laboratory evaporation method for the determination of pF-curves and unsaturated conductivity

The evaporation method according to Wind/Schindler is a simple and fast technique to determine retention curves of soil samples in standard 250 ml soil sampling rings. The unsaturated conductivity is determined by measuring the soil water tension with miniature Tensiometers in two levels inside the sample, and then correlated to the soil water tension or the moisture content.

Durner and Peters developed the robust correlation procedure to link the hydraulic functions (SHYPFIT 2.0, Peters and Durner, 2006b). The data is fitted to a selectable standard model, i. e. van Genuchten/Mualem, bimodal van Genuchten/Mualem or Brooks and Corey. The Model parameters can be set before, during or after a measuring procedure. Thus, the results are verified and the values for dry range and saturation are calculated according to the selected model.

The advantage compared to other methods is that the hydraulic properties are determined during a natural drying process of the soil.

HYPROP's outstanding features are the simple handling and the modular setup. For a start up you just need the HYPROP starter set and a scale. Existing laboratory scales, minimum requirements are a serial connection and a measuring range of 2000 grams, can be integrated. This set can be extended to up to 20 sample units.

Together with the correlation procedure you get a truly practical method which offers extraordinary results in the determination of hydraulic functions with low measuring expenditure.

Advantages

• Easy and flexible handling
• Usage of intact standard sampling rings without perforation
• Tensiometer shafts are installed into the sample from the bottom side
• Low expenditure of time and costs
• Suitable for mobile applications
• High-quality results for the water retention curve especially in the range close to saturation
• The hydraulic functions are consistently proved by numerous readings
• T5x Tensiometers may measure beyond 250 kPa due to boiling retardation
• The mathematical functions are profoundly adapted
• Simultaneous measurement of water retention curve and hydraulic conductivity
• Suitable for all soils (provided Tensiometers can be installed)
• No special requirements for the ambient conditions. Only the evaporation conditions should remain more or less constant during a measurement
• An existing scale with serial port can be connected to the system
• Extendable to up to 20 assemblies for one scale

Limitations

• The measuring range is limited to the measuring range of the Tensiometers
• Poor resolution of the hydraulic conductivity near saturation (particularly in sandy soils)

Technical Information

Included in Delivery

• Sensor unit
• Sensor unit connecting cable
• Soil sampling ring, 250 ml
• Silicone gasket
• Tensiometer shafts 12,5 mm and 37,5 mm
• Auger positioning tool
• Tensiometer auger
• Saturation bowl
• Refill set in carrying case
• Fibrous web, 15 cm x 15 cm
• tensioVIEW software on CD
• tensioLINK® USB adapter and connecting cable
• tensioLINK® T-piece junction plug
• Mains power supply unit