Reservoir planning ajitha miss

RESERVOIR PLANNINGRESERVOIR PLANNING

NECESSITY OF CREATING RESERVOIRSNECESSITY OF CREATING RESERVOIRS
 Retain excess water from periods of high flows for
use during periods of low flows
– Irrigation
– Development of hydroelectric power
– Water supply for domestic and industrial use
 Storage of flood water reduce flood damage
– Flood control
Single purpose reservoir Multi-purpose reservoir

INVESTIGATIONS FOR RESERVOIRINVESTIGATIONS FOR RESERVOIR
PLANNINGPLANNING
 1. Engineering surveys
 2. Geological investigations
 3. Hydrological investigations

ENGINEERING SURVEYSENGINEERING SURVEYS
 Area of the site (dam site, reservoir and associated works)
surveyed and contour map of the entire area is prepared
 From contour map, storage capacity and water spread area
of reservoir at various elevations can be determined
– Water spread area at any elevation determined by measuring the
area enclosed by the contour corresponding to that elevation with a
planimeter
– Storage capacity of reservoir determined by taking contour areas at
equal interval and summing up by trapezoidal formula, cone
formula or prismoidal formula

GEOLOGICAL INVESTIGATIONSGEOLOGICAL INVESTIGATIONS
 Geological investigations required to determine
– Suitability of foundation for dam
– Water tightness of the reservoir basin
– Location of quarry sites for obtaining suitable
construction materials

HYDROLOGICAL INVESTIGATIONSHYDROLOGICAL INVESTIGATIONS
 To estimate the quantity of water likely o be
available in river
– Study of runoff pattern of river at the proposed dam site
to determine the storage capacity of reservoir
– Determination of hydrograph of the worst flood to
determine the spillway capacity and design

SELECTION OF SITE FOR ASELECTION OF SITE FOR A
RESERVOIRRESERVOIR
 1. Suitable dam site must be available
 2. River valley at site
– Narrow so that the length of dam is less
– Open out at u/s to provide large basin for reservoir
storage
 3. Surrounding hills must be watertight
 4. Reservoir basin should be water tight

 5. Site should be such that minimum land and
property is submerged in the reservoir
 6. Site should be such that it should avoid those
tributaries which carries unusually high sediment
content
 7. Site should be such that adequate reservoir
capacity must be made available
RESERVOIR…RESERVOIR…

 8. As far as possible a deep reservoir must be
formed
– Land cost per unit capacity is low
– Less evaporation loss
– Less weed growth
 9. No minerals and objectionable salts present
 10.Quality of water available in reservoir should
be of good

ZONES OF STORAGE IN AZONES OF STORAGE IN A
RESERVOIRRESERVOIR

 Normal pool level (N.P.L)
– Maximum elevation to which water surface will rise in
the reservoir during normal operating conditions
– Also called as full reservoir level (F.R.L) or full tank
level (F.T.L)
 Minimum pool level
– Lowest elevation to which water is drawn from
reservoir under normal conditions

 Maximum pool level
– Maximum elevation to which water surface will rise in
reservoir during design flood (worst flood)
– Also known as maximum water level (M.W.L)

 Useful storage
– Volume water stored between normal pool level and
minimum pool level
– Also known as live storage as it can be used for various
purposes
 Dead storage
– Volume of water held below the minimum pool level
– It cannot be used for any purpose under normal
conditions

 Surcharge storage
– Volume water stored between normal pool level and
maximum pool level of reservoir
– Uncontrolled storage as it exists only during floods and
cannot be retained for later use

RESERVOIR YIELDRESERVOIR YIELD
 Reservoir yield
– The amount of water that can be supplied from a
reservoir in a specified interval of time
– Depend upon inflow and vary from year to year
 Safe yield of firm yield
– The maximum quantity of water which can be supplied
from the reservoir during a critical dry period
– The period of lowest natural flow of the stream is taken
as the critical period

 Secondary yield
– Quantity of water available in excess of safe yield
during periods of high flows
 Average yield
3
– Average of safe yield and secondary yield over a period
of time
 Design yield
– Value of yield adopted for design of a reservoir
– Should be such that the demands of consumers are met
with and storage is not unduly depleted
RESERVOIR YIELD…RESERVOIR YIELD…

RELATIONSHIP BETWEEN YIELD ANDRELATIONSHIP BETWEEN YIELD AND
STORAGESTORAGE
 Inflow – Yield = Change in storage
 If inflow is more than yield
– Storage will increase
 If inflow is less than yield
– Storage will be depleted

 1. Prepare a mass curve from flow hydrograph for
a number of consecutive years
 2. Corresponding to the given rate of demand,
prepare a demand curve
 3. Draw lines parallel to the demand curve and
tangential to the high points of the mass curve
(points at the beginning of dry periods)
DETERMINATION OF RESERVOIRDETERMINATION OF RESERVOIR
CAPACITY FOR A SPECIFIED YIELDCAPACITY FOR A SPECIFIED YIELD
OR DEMAND USING MASS CURVEOR DEMAND USING MASS CURVE

 4. Measure the maximum vertical intercepts
between the tangential lines and mass curve
– Vertical intercepts indicate the volume by which the
total flow in the stream falls short of the demand and
required to be provided from reservoir storage
 5. Determine the largest of the vertical intercept
measured in step 4 and this represents the
reservoir capacity required to satisfy the given
demand

1. Prepare a mass curve in the same manner
as in the previous case
2. Draw tangents at high points in such a
manner that their maximum departure from
the mass curve does nit exceed the given
capacity of reservoir
DETERMINATION OF YIELD FROM ADETERMINATION OF YIELD FROM A
RESERVOIR OF GIVEN CAPACITYRESERVOIR OF GIVEN CAPACITY

 3. Measure the slopes of these tangents and which
represents the yield which can be obtained in each
year from the reservoir of given capacity
– Slope of the fattest tangent is the safe yield

RESERVOIR LOSSESRESERVOIR LOSSES
Reservoir losses due to
– Evaporation
– Absorption
– Percolation

MEASURES TO REDUCEMEASURES TO REDUCE
EVAPORATION LOSS IN RESERVOIRSEVAPORATION LOSS IN RESERVOIRS
 By constructing reservoirs of less surface area
 By growing tall trees on the windward side of
reservoir which act as wind breakers
 By spraying certain chemicals which form thin
film above the water surface
 By removing weeds and plants from periphery of
the reservoir

 By providing coverings of thin polythene sheets
for water surface
 By developing underground reservoirs
 By growing huge trees and forest around reservoir
so that a cooler environment is formed
MEASURES TO REDUCEMEASURES TO REDUCE
EVAPORATION LOSS IN RESERVOIRSEVAPORATION LOSS IN RESERVOIRS

Reservoir planning ajitha miss

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Reservoir planning ajitha miss