Groundwater

Type of the method depends on the characteristic of the aquifer system, depth to the water level, extractable yield of the source, thickness of the regolith, accessibility of the location, demand of the users and available techniques and resources.

The most commonly used well types as follows :

Shallow Dug Well (Private / Common)

The most common source of water supply in Sri Lanka is for each household to have their own dug well or having common dug well for several users. The wells are normally dug in top the overburden to a depth slightly below the minimum water level in dry season. It is thus obvious that even a limited extra depletion of the groundwater level can result in numerous wells going dry. The selection of a suitable location is done by the uses and water quality is accepted by the taste, smell or colour of water. Wells are used for the drinking and the domestic purposes for a few people.

Shallow Productive / Agro Well

Shallow productive wells and Agro wells are used to extract large amount of water for an extensive drinking water project (about 600 families) or irrigation purposes. Large diameter (> 3 m) well is constructed by using excavator and systematic pumping test has to be done for the sustainable yield for long duration pumping.

Hand Pump Tube Well

Small diameter (110 mm) vertical hole is drilled by a drilling machine up to 100 m depth to extract water from the deep fractured aquifers. However, water from the overburden does not use for the tube well. Hand pump is installed if the yield is grater than 5 lpm.

Production Tube Well (Borehole)

Productive tube wells are used to extract large amount of water for an extensive drinking water project (about 1000 families). About 255 mm diameter well is used to extract water from the deep aquifers (up to 100 m) and systematic pumping test has to be done for the sustainable yield for long duration pumping.

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