Engineering investigations /surveys Geological investigations Hydrologic investigations SELECTION OF RESERVOIR SITE

1. PLANNING OF RESERVOIR
Water is one of the resources that cannot be generated
but only be preserved.
In future water scarcity will be one of the biggest challenges
in the World. The only way to conserve this resource is
through construction of Dams/Reservoirs.
Dams have been built for at least 5000 years and their functions
have evolved with the developing needs of the society.
Most likely, the Earliest Dams were built to store water for
Domestic Purpose and Agriculture Water Supply. With the
onset of Industrial Era, Hydropower became a major reason to
built dams.Choosing a suitable site is a crucial phase in Reservoir
Construction.
A well-selected site will not only give the optimum benefits, but
its Aesthetic Value may also create a recreational area surrounding
the reservoir. Conversely, a poorly selected site could cause
detrimental effects.

2. The investigations that are usually conducted
for reservoir planning
INVESTIGATIONS FOR RESERVOIR
Engineering investigations /surveys
Geological investigations
Hydrologic investigations

3. Generally Engineering Surveys are conducted for the dam, the
reservoir and their associated orcs. During this investigation
topographic survey of the area is carried out and the contour
plan prepared.
1) Engineering investigations /
surveys
The horizontal control is usually provided by
triangulation survey and vertical control precise
levelling..
For the reservoir, the contour plan is
Generally prepared to a scale of 1:15,000
with contour intervals between 2 to 3 m. The
area - elevation and storage-elevation curves
are prepared for different elevations up to
an elevation of 3 to 5 m higher than the
anticipated maximum water level

4. •In all the major Civil Engineering projects, geological advice
is considered 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.
2) Geological investigations
(i)Reservoir basin should be watertight
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.

5. • It is very important aspect of reservoir planning.
• To study the runoff pattern and to estimate yield.
• To determine the maximum discharge at the site.
• 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 depend upon the amount of available
water.
• Hence rainfall records, catchment
characteristics, spread of catchment,
climatic characteristics etc.
3) Hydrological investigations

6. SELECTION OF RESERVOIR SITE
A good site for a reservoir should have the following
characteristics :
Large storage capacity: The topography of the proposed
site should be such that the reservoir has a large capacity
for storing the water
Suitable site for the dam: A suitable site for the proposed
dam should be available on the downstream side of the
reservoir, with very good foundation, narrow opening in the
valley to provide minimum length of the dam and also the
cost of construction should be minimum.
Watertightness of the reservoir : Geology at the proposed
reservoir site should be such that the entire reservoir basin
is watertight. They should have Granite, Gneiss, Schists,
Slates, or Shales etc.

7. Good hydrological conditions: The hydrological conditions
of the river at the reservoir should give high yield.
Evaporation, transpiration, and percolation losses should be
minimum
Deep reservoir : The proposed site should be such that a
deep reservoir is formed after the dam construction. The
reason being evaporation losses would be minimum, in
addition to low cost of land acquisition and less weed
growth.
Minimum silt inflow: The life of reservoir is
defined by the quantity of silt inflow, which
means that, if the silt inflow is large, the life
would be less. Hence, it is necessary to select
the reservoir site at such a place, where the silt
inflow is minimum.
No objectionable minerals: The proposed site
should be free from soluble and objectionable
salts, which may pollute the reservoir.i)

8. THANK YOU