Boreholes over time, yield lower volumes of water compared to the time of commissioning. Several factors contribute to this occurrence. Of late, there is technology developed to inspect the boreholes whether in use or abandoned to ascertain the factors affecting the performance of the borehole or vice versa.
The first step is to measure the depth of the borehole using a depth measurement tool. This is done to compare the original depth with the current depth, and can indicate if siltation occurs.
Second is to measure water level in the borehole using water meter level that beeps when in contact with water. The static water level, when the pump is not in operation, tells the level of the groundwater.
Thirdly, lower a special camera into the borehole (camera inspection), to see if the inside of the borehole is damaged and to see if the screens, where the water flows into the borehole, are still clean.
A short Pump test is done to determine the specific capacity. This figure, tells about the amount the water level drops in the borehole versus the amount of water taken. This indicates how easy water flows into the borehole and what a sustainable level of abstraction is.
The sustainable abstraction rate can be affected by the type of soil in the aquifers and/or how clogged the screens are.
At the end of the exercise, an informed decision is made to abandon, re-use, resuscitate, etc.The pictures depict some of the stages in the borehole management process.
1. Uplifting a small pump from the borehole in readiness for camera inspection of the borehole
2. Uplifting the big and heavier pump from a borehole in readiness for camera inspection using a tripod stand (shyleck)
3. Measuring the depth of the borehole to detect sand accumulation level at the bottom of the borehole
4. Measuring the water level with a water level meter that emits sound when in contact with water