Research - Flowmeter 

Page / - last modified by TerraIndex TerraIndex on 2022/05/27 12:17 

Flowmeter 
last modified by TerraIndex TerraIndex
on 2022/05/27 12:17

Table of Contents

This technique is used to derive the (local) groundwater flow (direction and magnitude) directly around a horizontally placed monitoring well (local groundwater flow). For this, the flow meter is installed in a monitoring well. This measures the groundwater flow on the basis of the temperature trend in the monitoring well.
General information 	
Name	Flow meter, also known as Geoflow probe.
Alternative Technique: Phrealog.
NB not to be confused with the [ Geoflo ].	
Unit of measure and parameter	Temperature translated to groundwater flow (size and direction)	
Soil phase	groundwater	
Nature technique	Physical and probe/sensor	
Place of application	in situ	
Detection Mode	Measurement at ground level / water bottom	
Applicable in separate layers	Yes, minimum layer thickness: approx, 0.5 m	
Soil types for which technology is suitable	•	homogeneous well-permeable sand package
•	one sand package, with poorly permeable layers
•	anthropogenic	
Land soil/water bottom	Land soil	
Step in the data collection chain	Run-up, Drilling / Penetrating / Instr. Placement, Sampling or Measure	
Moment of availability results	Measurement results are available in the field	
Technology development phase	widening phase and applied routinely	
Method of purchasing	as service, as a product or as a device	
General description of the implementation method	A probe is installed in a horizontally slotted 2- or 4-inch standard monitoring well. The local groundwater flow (direction and magnitude) is derived using the probe.	
Working principle	The probe is installed in a horizontally slotted monitoring well. There is a heating element in the core of the probe. This element gives off a heat pulse. Around the core are a number of heat sensors/thermistors. The position of the sensors is precisely oriented with a compass. A resultant (vector) is obtained from the temperature differences between the heat sensors, which is representative of the groundwater flow direction and speed.
For each type of filter, the probe must be calibrated in a flow cell.	
Point / line measurement / volume measurement	point measurement	
Technical specifications
(including accuracy)	Measuring range: 0.03 m/day – 150 m/day
Sensitivity: 0.03m/day
Probe applicable in 2- or 4-inch monitoring wells	
Typical depth range	In practice monitoring wells are usually trenched to a depth of 10 meters. The length of the monitoring well is a maximum of 135 meters (cable length). Moreover the sensitivity is independent of the depth	
Time properties	Measuring takes approximately 2 hours. The method is suitable for repeat measurements to measure variations of the groundwater flow direction over time or to determine the direction accurately (at low groundwater flow rates).	
Measuring rate	If a suitable monitoring well is available, the measurement will take approximately 2 hours.	
Presentation results	Display derived groundwater flow (size and direction), including individual vectors	
cost	Approximately €150 per measurement, excluding advice and installing monitoring well.	
User information 	
Availability	one or a few providers in NL	
Is technology often used?	occasionally	
Research phase in which technology can be applied	Explore and monitoring	
Verification measurements / calibration measurements	are often used	
Frequently used application in practice	Establishing groundwater flow pattern in connection with the spread of groundwater contaminants, dimensioning cold-heat storage systems, monitoring landfills.	
Suitability	Suitable for saturated soil. In theory usable in any type of soil (clay, peat, sand). But in view of the measurement objective (horizontal groundwater flow) mainly to be used in aquifers (sandy) layers.
The measurements only provide a representative picture of the situation directly around the monitoring well (local groundwater flow). Due to differences in soil composition (also horizontal), it may deviate from the regional picture.
Measurement takes place in a small part of an (water-bearing) layer. The measurement does not have to be representative of the entire layer.
Measurement is influenced by local groundwater flow around the monitoring well and thus by the method of drilling and filter design.
Monitoring well must have a minimum inside diameter of 2 inches.	
Practical experiences in the Netherlands	The technique is still rarely used in practice. Where it is applied, the results are very useful. Given the results and the application for which the technology can be used, you would expect the technology to be used more often.	
“Dos“	Monitoring well must be placed level, otherwise an incorrect position of heat sensors will be calculated.
Place the sensor in a properly finished and constructed monitoring well (refill, filter).	
Also suitable for	Dimensioning ATES systems.	
Referentie
•	https://www.bodemrichtlijn.nl/Bibliotheek/bodemonderzoek/onderzoekstechnieken/flow-meter
•	US Forest Service
•	US Geological Survey
Flowmeter

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