Looking at the book Environmental Health Engineering in The Tropics: An Introductory Text by Sany Cairncross and Richard Feachem, published by Wiley it states that hand dug wells are the most common method of extracting water from the ground.
The wells can be constructed cheaply with local equipment and materials and water can be drawn using a bucket and rope which is initially cheaper than a pump and will be easier to fix or adapt when items fail.
Practical Action has used well with buckets in the more remote parts of Turkana, Kenya where there were problems with handpumps breaking and due to the remoteness of the location the handpumps could not be mended by people who would have used the water source. Some of the handpumps had fallen into disrepair and people then had to search for alternative sources of water which were not clean or reliable.
However, there are some obvious disadvantages with the increased potential for contamination and the difficulty in using a rope and bucket.
Further advantages of open wells include:
1) They provide extra storage - so in low permeability soil/rock water can slowly percolate into the well at night or when the well is not in use and then be drawn down less rapidly at peak times. 2) They can be covered and fitted with a handpump installation to reduce the potential for contamination - if the handpump breaks down, and is not able to be fixed, the users can remove the cover and still access the water. 3) They can be deepened if necessary.
Other contributors have given the advantages of open wells , see above. Indeed, the dug well is a good option for very small communities, hamlets and families. The biggest disadvantage of open wells is the risk for contamination of the water body, down in the well. We know that most contamination of the collected drinking water takes place during transport back home and at home. Nevertheless we need to create conditions to reduce the contamination risks at source. And there good solutions available to reduce these risks: lining of the well, sealing of the upper part of the lining, concrete, water tight concrete platform/apron, drainage, head wall, tight cover, fixed rope and bucket, stand for rope and bucket, and improved water lifting devices: wind lass, bucket pump, rope pump ….. However, probably the most important element for success is the attitude and behaviour towards water quality of the drawers of water, the family and the community at large. A participatory sanitary survey may help here. All these issues are described by WEDC, WHO, UNICEF, IRC etc. A contribution to that is the IRC publication of 1988 (!) Community Self-Improvement (see http://www.washdoc.info/docsearch/title/109585)
-Simple and easily understood and maintained
-Skills often available locally
-Comparing wells of similar depth, an open well has a large surface area and hence yield than a hand drilled well, but a hand drilled well can extend deeper into the aquifer
-Open wells can be covered and fitted with pump
-Hand drilled wells often cheaper and quicker to drill
-Open wells open to contamination from runoff, air borne pollutants and contamination of water lifting equipment
-Excavation dangerous and requires support in unsolidated ground
-Limited depth (due to labour requirements) so only suits shallow aquifers (<50m)
-Lifting water with windlass/bucket is labour intensive
Open wells are cheap, but prone to pollution. Their one advantage is that they can accommodate multiple users, making them especially useful & popular for watering livestock. For potable supply the well should be protected, and a hand pump fitted.
Here are a few general observations in response to the question
Advantages of Open Well
Easy access by bucket and rope means that there is no problem of pump breakdowns preventing access to water.
Assuming that a large diameter well is being compared with a narrow diameter borehole then the storage in the well itself is able toi fill up overnight and provide additional water during the day.
Disadvantages of Open Well
Low water quality as easily contaminated from surface runoff from surrounding area.
Contamination can also be introduced by buckets and ropes of multiple users - a single fixed bucket is better
Danger of people falling in.
Proper head-works, a wall and a concrete apron can reduce risks.
grond water contain large quantities of chlorides more than 250 ppm cause kidney problems,flurides more than 1.00 ppm cause flurosis,nitrates more than 45 ppm cause methemoglobinomia -blue baby born-and cause cancer.best solution is to harvest roof top of houses rain water filter and store in a sump and use to solve drinking water problems. Dr. H.R.Prakash rtd soil and water analyst agriculture department governament of karnataka
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