INVESTIGATIONS FOR RESERVOIR PLANNING

For any reservoir planning, various investigations, which are require to be carrie out, are the following:

1. Engineering Surveys.

The area of propose reservoir is extensively surveyed and contour plan is prepared.
Contour plan is very useful for fixing the height of the dam, evaluating the area that will be submerg and fixing the positions of spill ways, sluice ways and other river training works, require for the development of a reservoir.
Area-elevation curve and storage elevation curves can be draw from the contour plan which help in fixing the maximum operating Area-elevation and Volume-elevation curves.

Area elevation curve. Acontour plan of the proposed site of a reservoir is prepare.
Considering from the bottom let A1, A2, A3……An be the areas of successive contours.
These areas can be easily determine with the help of planimeter.
The value of area A1 is minimum at the base of the basin.
As elevation of the contours increases the area under them also increases.
A curve as CD between area elevation is shown in Fig. 9.2. Storage elevation curve.
The volume of storage corresponding to different contours can be calculat by using either prismoidal formula or trapezoidal formula.
We have seen that area of the contours goes on increasing as we proceed from bottom of the reservoir towards top.
Consequently volume of storage also goes on increasing as we procee from bottom of the reservoir towards top.
The volumes of storage for different contours may be calculated and curve between storage and elevation may be plott shown by curve AB

It is very important aspect of reservoir planning.
Capacity of reservoir, its potential for irrigation, power generation etc.
all depend upon the availability of water from the reservoir. Capacity of spillway, storage capacity, height of dam, etc.
all depen upon the amount of available water.
Hence rainfall records, catchment characteristics, spread of catchment, climatic characteristics etc.

In all the major Civil Engineering projects, geological advice is considere very essential.
It costs very little but relieves the Engineer from the worry of possible presence of fissure rocks or other geological faults which may cost too much when they come to notice later.

(i) Reservoir basin should be water tight without having any embedded fissured formations.

(ii) Position of ground water table.

(iii) Type of soil and its suitability in regard to foundation of the dam.

(iv) Type and depth of surface soils.

(v) Position of quarry sites for materials required for the construction of dam etc.

Trial pits may be bore in the catchment area and geological conditions investigated.