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SUSWA Knowledge Exchange
December 2014
Hydrogeological surveying
Collect and analyse existing sources of information:
- Existing boreholes/wells (depth, yield, g...
Hydrogeological surveying
Verify this hypothesis in the field:
- Look around (topography, geology, soils
- Make a profile ...
Geophysics
There is no machine that tells you where to drill to find
water and at what depth.
There are however several te...
Geophysics
How to measure under difficult circumstances (very dry
topsoil):
- Use long (1 m) electrodes
- Use stainless st...
Geophysics
After drilling:
Go back to your concept and verify your interpretation
(hydrogeology, topography, geophysics) a...
What should you demand from your
consultant?
In the TOR ask for:
- Note in the report the GPS coordinates + directions of ...
What should you do after field
surveying?
Store all information for each borehole (also the dry ones!) in
your office and ...
Water point mapping
Introduce a standard format to store information on
boreholes:
- Use this to store and share informati...
Sustainability
Are our boreholes sustainable?
- How much water are we extracting and how much water is
being recharged?
- ...
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Knowledge Exchange mission SUSWA project 2014 - Friday

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Knowledge Exchange mission SUSWA project
30 November – 5 December 2014, Kajiado, Kenya
Hydrogeological surveying and geophysics

Friday

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Knowledge Exchange mission SUSWA project 2014 - Friday

  1. 1. SUSWA Knowledge Exchange December 2014
  2. 2. Hydrogeological surveying Collect and analyse existing sources of information: - Existing boreholes/wells (depth, yield, geology, water quality, etc.) - Geological map + report - Topographic map - Google Earth Formulate a hypothesis: - Where could you find water and what type of aquifer do you expect? - How deep do you expect to strike the water?
  3. 3. Hydrogeological surveying Verify this hypothesis in the field: - Look around (topography, geology, soils - Make a profile (using your GPS measurements, or based on Google Earth or maps) - Water point mapping: verify the GPS coordinates of the nearby boreholes. Be there when the drilling takes place: This is the only moment you can actually touch your aquifer! - See the different types of geology encountered while drilling and at which levels they strike water. - Talk to the driller, ask him about drilling speed in the water bearing layers etc etc - Learn from this for future boreholes.
  4. 4. Geophysics There is no machine that tells you where to drill to find water and at what depth. There are however several techniques that can improve your change of success: - Sounding - Profiling according to your sounding (to determine electrode spacing) - Direction of the measurements according to the geology - Other Try to improve your concept together with your consultants using these techniques.
  5. 5. Geophysics How to measure under difficult circumstances (very dry topsoil): - Use long (1 m) electrodes - Use stainless steel potential electrodes - Add salt water around the electrodes - Increase the number of current electrodes - Take a Wenner sounding instead of Schlumberger You can help your consultant by giving him this information!
  6. 6. Geophysics After drilling: Go back to your concept and verify your interpretation (hydrogeology, topography, geophysics) and write down your conclusion in a report. Learn from this for future projects!
  7. 7. What should you demand from your consultant? In the TOR ask for: - Note in the report the GPS coordinates + directions of all geophysical measurements. - Note down the brand, type and serial number of the instrument used. - Note down which interpretation software has been used for interpreting the geophysical measurements. - A map showing: the locations of nearby boreholes, locations + directions of measurements, recommended site for drilling. - Present all VESses in 1 chart to allow good comparison. - Give the concept of which type of aquifer is to be expected and at what depth you could strike water.
  8. 8. What should you do after field surveying? Store all information for each borehole (also the dry ones!) in your office and digitally: - Location - Hydrogeological/Geophysical survey report - Borehole completion record - Drillers log - Test pumping - Water quality - Other observations of interest This information can help you (and your consultant) when you want to start a nearby project. Be there when the drilling takes place.
  9. 9. Water point mapping Introduce a standard format to store information on boreholes: - Use this to store and share information - This can be very valuable for future water projects - And this can help if quick interventions are required If you do this with all organisations within the Kenya WASH Alliance this can be beneficial for all.
  10. 10. Sustainability Are our boreholes sustainable? - How much water are we extracting and how much water is being recharged? - Are the waterlevels in the boreholes declining? Safe yield is not the same as sustainable yield! We might be mining our groundwater. In the long term this can cause many problems (dry boreholes, deeper and deeper boreholes, higher cost, more failed drillings, more expensive pumps required, etc.) Understanding the hydrogeological concept and monitoring of water levels is essential to understand if what we are doing is sustainable. Increasing the recharge and other water sources (3R) might be necessary to create a sustainable system.

Knowledge Exchange mission SUSWA project 30 November – 5 December 2014, Kajiado, Kenya Hydrogeological surveying and geophysics Friday

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