I have an area of 100 hectares (1km x 1km). Why do wells give me a different amount of water if they are drilled to the same depth?
The amount of water that a well contributes depends on the pressure of the aquifer, the thickness of the contributing layer, and its permeability.
For a well to be successful, it is necessary to look for areas of high permeability and the greatest possible thickness.
2. What is an Electrical Resistivity Tomography?
It is a high resolution system that injects an electrical current into the subsoil to measure the resistivity of the layers at different depths.
The following image is an example of an Electrical Resistivity Tomography, with which you can identify the bodies that are more likely to provide water as well as the characteristics to reduce the cost of drilling by being able to identify depth and avoid areas of high hardness which increases the cost of drilling.
3. I have seen those studies with 4 stakes and some cable reels, is it the same?
No. The resistivity study with 4 stakes is a Vertical Probe which is of low resolution and in most of the times it only reaches 200 meters of depth. As it is of low resolution, it has a greater margin of error, and even if the cables extend for a kilometer, it only provides data from the center.
In contrast, the tomography is high resolution (2,000 data per measurement), reaches a greater depth and provides data in its entirety.
4. Is there any technology that can tell me the amount of water that the well will provide?
Before drilling a well, there is no technology available on the market that can tell you how much water a well is going to provide.
Don't be fooled by people who irresponsibly value values without scientific backing.