Reservoir sedimentation causes and mitigation

1. ReseRvoiR sedimentation
Causes and mitigation

2. • GEOLOGICAL INVESTICATION
 ELEMENTS OF SEDIMENT MANAGEMENT
 CONTROL OF RESERVOIR SEDIMENTATION
 DESILTING METHOD
 CONCLUSION
 REFRENCE

3. The geologic conditions that exist at and in the vicinity of
every proposed dam and reservoir should be known and
understood by those responsible for its planning and design.
The principal elements that must be considered are
 Geomorphology
 Hydrology
 Hydrogeology
 Geology

4. Geomorphology
In the geological sense, geomorphology in the reservoir should
be stable and the configuration of the land surface, and it includes
the location, size, and shape of such physical features as hills, ridges
valleys, streams, and Lakes.
Topographic maps show these features .
Hydrology
Hydrology is the science relating to the water of the earth , its
distribution and its phenomena. To be successful, a dam and reservoir
project must have an adequate and continuous supply of water suitable
for theory intended uses of the reservoir. Hydrologic information and
investigation will be required in varying degree, depending upon the
size of the project . The annual rainfall, the ratio of watershed area to
reservoir area, and the volume of stream flow at all seasons of the year
must be known.

5. Hydrogeology
 Hydrogeology to determine whether ground water would
contribute to the reservoir or whether the reservoir would lose
water to the ground-water system is also essential. The
reservoir capacity and maximum and minimum reservoir yield
also must be known so that commitments for water will not
exceed the quantity of water available.
Geology
 It has been said that construction of a dam and reservoir causes
more interference with natural conditions than does any other civil
engineering operation. Knowledge of the geological situation is
essential as a basis for sound engineering, especially in the
investigation of dam and reservoir sites, for an error in geological
interpretation or the failure to discover some relatively minor
geologic detail may be costly and sometimes Hazardous.

6.  Reduce sediment inflow
sediment delivery to the reservoir can be reduced by techniques such
as erosion control and upstream sediment trapping.
 Route sediments
Some or all of the inflowing sediment load may be hydraulically
routed beyond the storage pool by techniques such as drawdown
during sediment-laden floods, off-stream reservoirs, sediment bypass,
and venting of turbid density currents.
 Sediment removal
Deposited sediments may be periodically removed by hydraulic
flushing, hydraulic dredging, or dry excavation.

7. Provide large storage volume
Reservoir benefits may be considered sustainable if a
storage volume is provided that exceeds the volume of
the sediment supply in the watershed. The required
sediment storage volume may be included within the
reservoir pool or in one or more impoundments.
Sediment placement
Focus sediment deposition in areas where its
subsequent removal is facilitated, or where it minimizes
interference with reservoir operation. Configure intakes
and other facilities to minimize interference from
transported or deposited sediments...

8. Check Dam
check dam is a small dam, which can be either temporary or
permanent, built across a minor channel, swale, bioswale, or
drainage ditch. Similar to drop structures in purpose, they
reduce erosion and gullying in the channel and allow
sediments and pollutants to settle.

9. Afforestation

10.  Essential measures to alleviate the sedimentation of
reservoirs are to reduce the sediment entering the channel
and increase the sediment flushing rate. Some efficient
measures are listed in follows.

12. Check_Dam across Kallada river Elephanta check dam

13. Using the operation of storing clean water and
discharging muddy flow to mitigate reservoir
sedimentation.

14. Desilting

15. Kallarkutty Dam,Kerala
Discoloured Periyar,Kerala

16. Desilting Methods

18.  Geological investigation well done before the planning
and design of any reservoir/Dam.
 Elements of Sediment Management are Reduce
sediment inflow, Route removal, Provide large storage
value, sediment placement, afforestation,checkdam.
 There is no doubt that India’s water storage reservoir
are silting up.
 Silt deposits have reduced the water storage capacity
by 30-40 % in major Dams.
 The desilting in any reservoir in the region is to carried
out only during the Summer season .

19.  W.Calhoun Smith(Dec 1966),Geological Factors in Dam and
Reservoir Planning,Illinoin State Geological Survey,pp5-15.
 Gregory L.Morris,Jaihua Fan(Dec 2010)Reservoir
Sedimentation Handbook,Mcgraw Hill Book Newyork,ver1.04
,pp50-62,115-119,565-570,720-723.
 Joseph Sebastin Paimpillil(2009),Reservoir Desiltation and its
impact on wetland water quality. Center for Earth Science
abd Environmental Management ,cochin .
 Sedimentation in Our Reservoirs:Causes and Solutions,
Kansas Water Resources Institute.
Website
 http://ida.water.usgs.gov/ressed/
 http://www.usbr.gov/pmts/sediment/
 www.wikipedia.com

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