Groundwater search in North-Africa, which technique?

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Groundwater search in North-Africa, which technique?

Post by Waterman »

Dear specialists,

I am interested in helping(non-profit) farmers in North-Africa (Morocco) to find drilling well spots more efficiently. Now they mostly use dowsing rods to find spots to drill. I have read about different techniques and devices to prospect/measure water aquifers.
The depth ranges from 50 to 200 meters, mostly they find water around 130/150 meters, sometimes salty. The soil is mostly dry sand/rock.
What is the best technique? Is resistivity the best option? It should be easy to operate and not expensive.
I have found some devices and would like to have your opinion as professionals.(I am just a medical doctor with some phisics knowledge)
- PQWT (for example the s500 model)
- GER River G
- Syscal system from IRIS

Please help me on my quest and many thanx for your reply!!

Greets
Noa
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Re: Groundwater search in North-Africa, which technique?

Post by geophix »

I would choose one with an active energy source instead of relying on passive sources. It feels more reliable. So I would not choose PQWT. I have used a Syscal system from IRIS so I have confidence in it for shallow investigation (around 50 feet to 100 feet), but I don't know whether it has corresponding cable lengths and power sources for deep penetration. I don't know how GER River G works, but it looks like it's designed for easy use for water exploration.
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Re: Groundwater search in North-Africa, which technique?

Post by Waterman »

Thank you for your reply geophix!

Is there someone else who has experience with any device on the depth of 50-200 meters?
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Re: Groundwater search in North-Africa, which technique?

Post by markg21ca »

Speaking to your comment about the possible salinity of your target, there could be a significant enough of a resistivity contrast between the aquifer and the surrounding material to consider adding EM soundings to your short list of methods. There are plenty of easy to use instruments out there that will do the job (i.e. Geonics) at the depth range and with the target geometry you mention.
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Re: Groundwater search in North-Africa, which technique?

Post by 99thpercentile »

There are a number of legitimate geophysical methods to look for groundwater, and a number of fraudulent instruments sold as water detectors. There is no such instrument as a water detector, so if someone tries to sell you something called a water detector you should run away quickly.

I have years of experience doing this and there are a handful of methods that work, but there are several questions to ask first. Do you want to put a well at a specific location, if so you may either not be able to drill deep enough if there is water there or it may just be a bad location. The correct approach is to have a general area, say a 5 to 10 mile radius, then follow the standard workflow to pick the best location. You start with remote sensing methods such as Google Earth Imagery and geologic maps.

Then after deciding on a smaller area, you probably want a screening tool like mobile time domain electromagnetic induction (TDEM). The Loupe instrument can image to about 25 m, while the Aarhus Geoinstruments tTEM can image to 100 m. If you can refine your locations from the screening survey, you may need to follow up with electrical resistivity tomography (ERT).

It is easier in much of the USA as many states have a database of all water wells. This information can be used to estimate locations and depths for new wells.
Ryan E. North, PhD, RPG, GISP
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ISC Geoscience
ryan.e.north@iscgeoscience.com
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Re: Groundwater search in North-Africa, which technique?

Post by Waterman »

Thank you very much 99th!
I need to search specific plots of land (personal of the farmers) mostly ranging from 1 hectare to 10, average 2 hectares.
So you say a combination TDEM and ERT.
I see that the Loupe TDEM has a range around 20-30meters but the water level is mostly around 120-140 meters.

Would you please be so kind and helpful to give advice in brand and type of the devices. Price needs to be between $4000 and max €8000 for the project to be a succes.
Again Thanx for all your help guys!
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