| Wells construction: hand dug and hand drilled |
|Section one: Planning|
|Chapter 1: Introduction to wells planning|
Locating the site for a well should be based on the following guidelines:
The well should be located at a site that is:
• water bearing;
• acceptable to the local community;
• suitable to the sinking methods available;
• not likely to be easily contaminated.
It is not always possible for a site to meet all of these guidelines. Therefore, a site will need to be chosen which best approximates the guidelines, with particular emphasis on the likelihood of reaching water (see Fig. 12). Where there is an equal chance of reaching water at several different locations, the one closest to the users is preferable.
• Where is water likely to be found?
A development worker can assist the community's effort to locate a likely site by collecting available information on local ground water. In many countries, some information is available through appropriate ministries, water agencies, and international development organizations.
Choosing the site for a well can be difficult, because easily available and abundant water can never be guaranteed. Even professionals, before a well is sunk, rarely know where they will reach water and how much will be available. However, there are a number of guidelines which can be very useful in providing information about possibly successful well sites.
Where possible, a well can be located near a past or present water source. By doing so, you are likely to reach water at approximately the same depth as the other source.
If no other sources exist or have ever been developed nearby, you must be more cautious in choosing a well site. Unless you have the benefit of detailed geological information, it is best simply to look for the lowest spot nearby. Both surface and ground water are likely to collect here. In some cases, plants can be indicators of the presence of ground water (see Appendix, Vegetation as an Indicator of Ground Water). However, be careful not to build in a place so low that the well would be susceptible to flooding in heavy rain.
1) Limited water would be available at this site, because the impermeable rock layer is close to the ground surface, allowing slight fluctuations in the water table to drastically affect water availability.
2) Closest site to village and therefore the best site if it is possible to dig down far enough to reach water.
3) At this site, there would be a better chance of reaching more water that at 2. but the site is further from the village.
4) This is the site where water is most likely to reached by a well although it is some distance from the village. Because it is in the absolute bottom of the valley, it may be subject to flooding.
• Is the site acceptable to the local community?
The community must accept the final site choice and be willing to use the well when it is completed. Only then will it benefit local residents.
• Is the site suitable to the available sinking methods?
If the most likely site would require that the well penetrate a layer of rock, and if there are no tools available to do so difficult a job, the site is not an appropriate one.
• Is the well likely to be easily contaminated?
The most important consideration here is that the well not be located within 15 meters of a latrine or other sewage source. This would also include not placing the well where it might be damaged or inundated by a flood or heavy rain.