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Reservoir sedimentation causes sedimentation

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Seminar On Reservoir Sedimentation Causes & mitigation
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Seminar OnReservoir

Sedimentation Causes & mitigation

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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

Geological Investigation

Geomorphology Hydrology Hydrogeology Geology

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Geomorphology In the geological sense, geomorphology is 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.

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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 causesmore 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 theinvestigation 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.

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1. Reduce sediment inflow sediment delivery to the reservoir can be reduced by techniques such as erosion control and upstream sediment trapping.

2. Route sedimentsSome 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.

3. Sediment removalDeposited sediments may be periodically removed by hydraulic flushing, hydraulic dredging, or dry excavation.

Elements of Sediment Management

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Provide large storage volumeReservoir benefits may be considered sustainable if a storage volume is provided that exceeds the volume of the sediment supply in the us watershed. The required sediment storage volume may be included within the reservoir pool or in one

or more us 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.

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Afforestation Afforestation for reservoir protection should be carried out in a scientific manner ; and to aid in accomplishing this. Proper afforestation will not only provide the desirable qualities of watershed protection.

Check Dam  check dam is a small dam, which can be either temporary or permanent, built across a minorchannel, 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

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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.

Control of Reservoir Sedimentation

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Using water and soil conservation and check dams to decrease sediment yield, to reduce sediment entering the channel, and finally to alleviate reservoir sedimentation.

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Using the operation of storing clean water and discharging muddy flow to mitigate reservoir sedimentation. Low water levels are used during flood season to discharge more sediment, and high water levels can be operated during dry season.

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Check_Dam across Kallada river Elephanta check dam

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DesiltingOver a period of years, as they fill with mud, silt and plant materials, many lakes and reservior will require desilting. 

Desilting might also be needed when there is a large accumulation of semi-decomposed leaf litter and other organic debris. This material tends to reduce oxygen levels in the pond or lake, and because it often produces acidic conditions, it can reduce the fertility of the pond or lake.

Desilting is undoubtedly an art form, but, with specialist machinery and skilled operators, Aquascapers is able to successfully desilt all types of ponds,lakes reservoirs.

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Kallarkutty Dam,Kerala

Discoloured Periyar,Kerala

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Desilting Methods

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Geological investigation well done before the planning and design of any reservior/Dam.

There is no doubt thet India’s water stroage reservoir are silting up.

Silt deposits had reduced the water stroage capacity by 30-40 % in major Dams.

The desilting in any reservoir in the region is to carried ourt only during the south west Monsoon time.


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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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