Cover Image
close this book Wells construction: hand dug and hand drilled
View the document Acknowledgments
View the document Introduction
close this folder Section one: Planning
close this folder Chapter 1: Introduction to wells planning
View the document A. Overview
View the document B. The need for adequate water supply
View the document C. Involving the local community
View the document D. Selecting the most appropriate water source
View the document E. Site choice
View the document F. Preventing water contamination
View the document G. Types of wells
View the document H. Well sections
View the document I. Materials
View the document J. Tools and equipment
View the document K. Sinking method
View the document L. Preparation for construction
View the document M. Planning
close this folder Section two: Hand dug wells
View the document Chapter 2: Introduction to hand-dug wells
View the document Chapter 3: Well design
View the document Chapter 4: Supplies
View the document Chapter 5: Lowering and raising workers and equipment
View the document Chapter 6: Digging
View the document Chapter 7: The middle section: overview of lining techniques
View the document Chapter 8: Construction of the middle section
View the document Chapter 9: Construction of the bottom section
close this folder Section three: Drilled wells
View the document Chapter 10: Introduction to drilled wells
View the document Chapter 11: Drilling and casing techniques
View the document Chapter 12: Construction: hand rotary and hand percussion methods
View the document Chapter 13: Construction: sludger method
View the document Chapter 14: Construction: driven and jetted
View the document Chapter 15: The bottom section
close this folder Appendices
View the document Appendix I: Conversion factors and tables
View the document Appendix II: Vegetation as an index of ground water
View the document Appendix III: Uses of dynamite in hand dug wells
View the document Appendix IV: Cement
View the document Appendix V: Leveling and plumbing the mold
View the document Appendix VI: Pipe
View the document Appendix VII: Pumps
View the document Appendix VIII: Water treatment in wells
View the document Appendix IX: Rope strength
View the document Glossary
View the document Annotated bibliography

E. Site choice

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.


FIG. 1-2. POSSIBLE WELL SITES

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.