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Enabling better global research outcomes in soil, plant & environmental monitoring.

G-2 Drain Gauge

The G-2 Drain Gauge is a Wick Lysimeter designed for long-term measurements with little maintenance. Water is emptied from the monitor through a siphon. Because there are no moving parts, the Drain Gauge is tough. It's built to be buried—and stay buried. You don’t need to worry about digging it up for maintenance or inspection. Installation is easy - simply dig a shaft with an auger, or even a post hole digger and shovel. Then drop in the monitor, re-fill the hole, and begin taking measurements.

Drain Gauge 2 Features
Monitor Groundwater Leaching
Use the Drain Gauge G2 to determine the volume of water and chemicals draining from the vadose zone into groundwater.

Identify Contamination
The one-and-a-half meter tall Drain Gauge is buried directly in the ground to measure flow rate in unsaturated soils and collect soil water samples for chemical analysis. Water samples can be collected easily through a surface port to analyse for chemicals, fertilisers, and other contaminants.

Measure Deep Percolation Accurately
One of the challenges with lysimeter measurements is that water tends to flow around receptacles buried in the ground. The drain gauge uses an ingenious duct and wick design to apply a constant tension and keep the flow rate within the gauge equivalent to the flow rate in the surrounding soil.

Made from Non-reactive Materials
The Drain Gauge is constructed from inert materials, so chemicals won’t react with the tube, the sensors, or the collection reservoir.


  • Waste Landfill Sites. Used to identify drainage and monitor efficacy of cover systems.
  • Food Processing Waste Sites. Maximises applications by monitoring water drainage rates and water quality below the root zone.
  • Environmental research. Measures percolation and recharge rates.
  • Farming operations. Measures and informs irrigation during a cropping season.
  • Golf Courses. Used to measure and control excess water applications and fertiliser loss.

High water tables can flood measurement chambers, causing errors in drainage measurements.


DCT water interception: 1.6mm per drain, ± 0.03mm
Reservoir drain volume: 50ml
Water level gauge resolution: 1ml or better
Measurement time: 10ms
Gauge power: 2.5VDC @ 3mA, for 10ms
Output: Proportional mv-to-water-level
Operating temperature: 0–50°C
Cable length: 3m
Reservoir sampling tube length: 3m
Wick: 60cm inert fibreglass
Construction Material: Steel
Overall length: 147cm
Weight: 10kg boxed
Warranty: 1 year

The Drain Gauge is first installed below the root zone. Water infiltrates down through the divergence control tube, and then down a fibreglass wick into a collector. As collected water fills the measurement reservoir, the water level is monitored by a water depth sensor. When the water level in the measurement reservoir reaches the top of the siphon tube, the water empties and the event is recorded by an attached data logger. The emptied water then drains into the sampling reservoir. A sampling syringe, attached to the water reservoir sampling port (blue tube), can draw water samples out of the sampling reservoir for chemical analysis. Excess water drains out of an overflow port and into the soil while allowing a volume of water to remain for sampling.

Drain Gauge References
Cobos, D.R., Salinity Effects on Drainage Measurement with the Gee Passive Capillary Lysimeter: 1-4.

Corwin, D.L. 2000, ‘Evaluation of a Simple Lysimeter-design Modification to Minimize Sidewall Flow’, Journal of Contaminant Hydrology, vol. 42, pp. 35-49.

Gee, G.W., Ward, A.L., Caldwell, T.G. and Ritter, J.C. 2002, ‘A Vadose Zone Water Fluxmeter with Divergence Control’, Water Resources Research, vol. 38, no. 8, pp. 10.1029/2001WR000816.

Gee, G.W., Zhang, Z.F., Ward, A.L. and Keller, J.M. 2004, Passive-wick Water Fluxmeters: Theory and Practice, SuperSoil 2004: Third Australian New Zealand Soils Conference, University of Sydney, Australia. pp. 1-9.

Guber, A.K., Pachepsky, Y.A., van Genuchten, M.Th., Rawls, W.J., Simunek, J., Jacques, D., Nicholson, T.J. and Cady, R.E. 2006, ‘Field-Scale Water Flow Simulations Using Ensembles of Pedotransfer Functions for Soil Water Retention’, Vadose Zone Journal, vol. 5, pp. 234-247.

Louie, M.J., Shelby, P.M., Smesrud, J.S., Gatchell, L.O. and Selker, J.S. 2000, ‘Field Evaluation of Passive Capillary Samplers for Estimating Groundwater Recharge’, Water Resources Research, vol. 36, no. 9, pp. 2407-2416.

Mertens, J., Diels, J., Feyen, J. and Vanderborght, J. 2007, ‘Numerical Analysis of Passive Capillary Wick Samplers prior to Field Installation’, Soil Science Society of America Journal, vol. 71, no. 1, pp. 35-42.