Lesson 3: CONSTRUCTION OF SMALL EARTH-DAMS

=Introduction= Small-dams are structures that are constructed across streams/rivers to create artificial lake or reservoir behind themselves. The purposes which these reservoirs are meant to serve may be either for flood control or conservation purposes. Conservation of water may be required for any one or more of the following purposes-irrigation, domestic water supply or livestock water supply. Generally these dams have different sizes, but typical small-earth dams have the following dimensions: Length-60m, depth-3m and width-5 to 10m. The construction of this type of dams can be done using human labour, draft power or machinery.

There are important things to consider before, during and after construction of the dam. These are;
 * To choose a suitable area for construction of the dam wall.
 * To choose, and collect construction equipment, tools and materials.
 * To select a good method of construction of the dam.
 * To follow up proper ways of construction.
 * Measures to avoid destruction and siltation of the dam.

=Selection of a suitable dam site=

In order to get a suitable area for construction of the dam, the following factors have to be looked into and examined thoroughly:-

=Identification, selection and collection of construction equipment, tools and materials and labour availability=

Large quantities of construction materials are required to build the structure of an earth dam. It is therefore necessary for economic feasibility that the bulk of the materials required for the dam should be available in close vicinity of the site. In the construction of small earth-dams, the tools and materials required may include some of the following:

=Conditions to be observed when constructing an earth-dam=

Earth dams can be built by using different methods. Examples include; human labour, animal draft power or machinery. However, the use of machinery or animal draft power will save time. Good supervision during construction will determine the quality of the dam and whatever method is used the following conditions should be adhered to:

=Planning and design of a small earth dams=

It is not the intension of this lesson to give detailed planning and design of small earth dams. However. An attempt is made to give some highlights on this.

=Steps to follow during the construction of an earth dam=

After choosing a suitable site for the dam, it is important to follow the following steps during and while constructing the earth dam. =References= Sokoine University of Agriculture, Computer Center

Glenn. O. Schwab, Kenneth K. Barnes, Richard K. Frevert and Talcott W. Edminster (1971). Elementary Soil and Water Engineering 2nd Edition) 193pp, 196pp, 201pp.