Measuring Soil Water Potential Near A Wetland

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Sep 5, 2007, 2:48:59 PM9/5/07
to sowacs: soil water moisture content measurement systems and sensors
We are interested in purchasing soil water potential sensors to
measure the soil water potential at 1 and 3 feet below land surface
(BLS). The scope of the project is to determine the source of water
supporting a wetland. Two sensors will be installed at two
locations. We need to accurately determine the difference in soil
water potential vertically. Since the study area is located near a
wetland we are expecting very low soil water potential readings (0-20
cbars). Therefore, we need a sensor that is accurate, easy to install
and moderately priced. Any suggestions?



Jochen Eberhard

Sep 5, 2007, 7:17:20 PM9/5/07

check out the special tensiometers for nurseries and greenhouse
applications. They are made out of very porous material in order to work
very fast at the wet end.

Best regards,


Jochen Eberhard, Dipl.-Ing.agr. (Hohenheim), Dr.Agr.(TUM)

Irrigation Researcher/Agronomist

NCEA (National Centre for Engineering in Agriculture)

University of Southern Queensland

West Street

Toowoomba 4350


Tel: +61 (0)7 4631 1989

mobile: +61 (0)428 765 372

Fax: +61 (0)7 4631 1870


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Sep 5, 2007, 8:18:12 PM9/5/07
Hi guys,
any one who knows where I can buy a flow meter module from?
I am designing a system and need a flow meter that ouputs raw reading -
analog or digital output that I can interface to another circuit. (not self contained).

Sep 5, 2007, 8:34:51 PM9/5/07

I haven't gone to any of these sites, but a quick search came up with these:

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James Kennedy

Sep 6, 2007, 12:52:27 AM9/6/07
I would suggest a watermark sensor and a Hobo logger.

Eienaar Kennedy Besproeiing
Posbus 30309
South Africa
Website :,,
Tel: +27-51-4225767
Fax: +27-51-4225766
Sel :(+27) 0839627305
Skype VoIp : jameskennedybloemfontein

James Kennedy

Sep 6, 2007, 12:53:55 AM9/6/07

I would suggest McCrometers's, McPropeller,


Eienaar Kennedy Besproeiing

Jochen Eberhard

Sep 6, 2007, 12:59:40 AM9/6/07
I thought watermark sensors wouldn't be very accurate between 0 and

Best regards,


> -----Original Message-----
> From: [] On

This email (including any attached files) is confidential and is for the

Skewes, Mark (PIRSA)

Sep 6, 2007, 1:09:10 AM9/6/07
I agree with the comment about sensitivity of Watermark Sensors at low tension (0-10kPa).

Here in South Australia we have monitored drainage using paired tensiometers, we have used T4 and T8 tensiometers from UMS in Germany. These are both loggable, refillable tensiometers, the T8's will tell you when they need refilling.

We log the tensiometers using systems developed here in SA by a local electronics company, Measurement Engineering Australia, but I am sure that UMS would have their own logging products. Cost is not dirt cheap, T4's are cheaper than T8's.

Hope this helps,

Mark Skewes
Research Scientist (Water Resources and Irrigated Crops)
South Australian Research and Development Institute
Loxton Research Centre, Bookpurnong Road, Loxton
PO Box 411, Loxton SA 5333
DX 52102
T: 61+8+8595 9149 F: 61+8+8595 9199 M: 0408 800 681
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Oscar Cainelli

Sep 6, 2007, 4:32:17 AM9/6/07
I agree completely with Mark Skewes, we are actually using in laboratory the
mini tensiometers T5 from UMS and they are very accurate (+- 0.2Kpa) and
quick responding. I guess that T4 and T8 hold similar characteristics.

The price for the T5 is roughly 400 euros each (I recently ordered a couple
more of them). I don't know about the price of the T4 and T8 but I guess
they should be lower than that of T5.

Good luck

PhD ing. Oscar Cainelli
Civil & Environmental Dept.
University of Trento
Via Mesiano 77
38050 Povo di Trento (TN)
tel. +390461882637

Rodney Thompson

Sep 6, 2007, 10:53:11 AM9/6/07
For soil matric potential measurement in the 0 to -10 kPa, the Watermark is not at its best.  We evaluated the performance of the Watermark with different  calibration equations, and once in the  0 to -10 kPa range, the Watermark becomes unresponsive, with the maximum value for a given soil being determined by the calibration equation used (see Thompson et al 2006, Evaluation of the watermark sensor for use with drip irrigated vegetable crops. Irrigation Science, 24, 185-202).

We used tensiometers from Skye Instruments (Model SKT 600/IE) to measure in this range.  They appreciably cheaper than the price mentioned for the T5; however, they require an in-house logger which appreciably increases the price of the overall package.  Also, their working range is 0 to -80 kPa, so they may not have best resolution for the small range of interest here. 

Something that may be of interest is the Irrometer MLT-RSU small tensiometer.  It has 4-20 mA output and is offered  with two calibrations of 0 to -16 and 0 to -32 kPa.  I think they are about half of the price mentioned for the T5.  A colleague used them in perlite in a greenhouse and seemed reasonably happy with them. I don't have any information on how they perform in soil under field conditions.

Rod Thompson
University of Almeria,

Universidad de Almería,
Dpto. Producción Vegetal,
Edificio CITE-2B,
La Cañada

Tel: ++34 638140123
Fax: ++34 950 015939

Lauren Bissey

Sep 6, 2007, 11:51:54 AM9/6/07
The UMS tensiometers can be logged by Campbell Scientific data loggers.

Lauren Bissey

Hope this helps,

Best regards,



---------- Original Message ----------

FROM: "Skewes, Mark \(PIRSA\)" <>
TO: <>
DATE: Thu, 6 Sep 2007 14:39:10 +0930

SUBJECT: RE: Measuring Soil Water Potential Near A Wetland

Hope this helps,

Best regards,


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