The SWS Well-Jetting Technique
Before summarising the applications and advantages of the various well jetting techniques let us tell you something about our involvement with one particular project. In 1982 SWS was invited to demonstrate well-jetting to the World Bank funded Kano Agricultural and Rural Development Programme in Northern Nigeria. This is an area crossed by many seasonal rivers, that is, rivers which only flow for a short time following storms, but for the rest of the year they appear to be just broad sandy dry river beds.
During October and November Richard Cansdale, SWS Filtration’s Director, taught four teams of project staff how to insert well points deep into these sandy river beds using portable engine pumps. Within twelve months several hundred wells had been installed using this technique, and now fifteen years later, not only have thousands of these small wells been installed, but “washbore” the word describing them, has entered the local language. The majority of these wells are put down by farmers to irrigate their crops during the dry season, but others are used for domestic water supplies.
During a return visit in 1987 Richard Cansdale saw the need for a modified wellscreen and SWS Filtration can now offer a self-jetting wellscreen which is even easier to install than the original type. Please now study the various applications and advantages of well-jetting and if you would like further information please contact SWS.
Well-jetting is a simple technique for inserting small diameter wellscreens into shallow sandy water bearing aquifers. Unlike conventional boreholes which require heavy drilling equipment, well-jetting is carried out by hand using just one or two portable engine pumps to produce a powerful jet of water.
Where can Well-Jetting be used?
Well-jetting is particularly suitable for sandy river beds, wadis or river banks where water can be found close to the surface. In some flood plains it is possible to jet through more than 30 m of silt before reaching a sandy aquifer but most commonly well-jetting penetrates no more than 6 or 10 metres.
Well-jetting may be used to supply water for:-
|Irrigation ||- large or small scale.
|Domestic water supplies ||- for individual households, villages or small towns.
|Livestock watering ||- particularly from dry river beds.
|De-watering ||- lowers water table before laying down foundations.
|Filtered sea water ||- when drawing from sandy sea beaches.
Advantages of the Well-Jetting technique
|Easy installation ||- individual teams can install up to 6 wells/day.
|Inexpensive equipment ||- quite affordable by individual farmers or families.
|Lightweight equipment ||- does not require heavy drilling rig.
|Easy transportation ||- can be carried in just a pick up or Landrover.
|Cleaner water ||- the water is much cleaner than in polluted open wells.
Usually it is quite safe to drink.
|Saves land and labour ||- instead of digging a large pit which may have to be deepened throughout the dry season a single small diameter well takes up no significant space.
|Reduces water loss ||- no water is lost through evaporation from open pits.
Different Well-Jetting techniques
Just as ground conditions vary, so the well-jetting technique itself may be varied to suit a particular situation. Screens with different diameters or slot sizes may be used while in fine sand they may be wrapped with a geotextile. With deeper wells a temporary tripod or truck mounted hoist can sometimes assist while for easy installation and speed the SWS self-jetting screen has proved most successful.