**7.2 Geological influences upon the selection of reservoir sites**

*Topography*: In the geological sense, topography is the composition of the Earth's surface, and includes the location, size and shape of physical features such as hills, hills, valleys, streams, and lakes. Topographic maps show these features. Examination of a topographic map combined with a survey of the land is often sufficient to determine the overall topographical suitability of the dam and the location of the proposed reservoir. This is the first and easiest step in determining the feasibility of a proposed project [25].

*Hydrology and Hydrogeology*: Hydrology is the science related to the Earth's water, its distribution and phenomena. For a dam and reservoir project to be successful, it must have an adequate and continuous supply of water suitable for the tank's intended uses. Hydrological information and investigations will be required to varying degrees, depending on the size of the project. Annual rainfall, the ratio of the catchment area to the reservoir area, and the size of the stream flow must be known in all seasons of the year. It is also necessary to study groundwater science to determine whether the groundwater will contribute to the reservoir or whether the reservoir will lose water to the groundwater system. Tank capacity, maximum and minimum tank yield must also be known so that water commitments do not exceed the amount of water available [25].

*Geology*: To properly judge the feasibility of the proposed dam and reservoir project, it is necessary to know the type, distribution and succession of rocks and other geological units in the project area, for the stability of the dam and water - the ability to maintain the reservoir is directly related to them. The aspects of geology that must be evaluated to determine the suitability of a project site include:


The engineering properties of the geological units are directly related to the type of rocks or unconsolidated material involved, and thus to the geology [25].
