gtu shantilal shah engineering college, bhavnagar...around 40,000 large reservoirs worldwide used...

Shantilal Shah Engineering College, Bhavnagar GTU

Around 40,000 large reservoirs worldwide used for water supply, power generation, flood control etc.

About 1 % of the total storage volume is lost annually as a result of sedimentation and 300 to 400 dams would need to be constructed annually to maintain current total storage.

Palmieri et al., (2003) estimated the storage loss to be approximately 45 km3 per year.

SEDIMENT CONTROL MEASURES IN RESERVOIR

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[Source: ICOLD Report, 2004] SEDIMENT CONTROL MEASURES IN RESERVOIR

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[Source: UNEP Report, 2004] SEDIMENT CONTROL MEASURES IN RESERVOIR

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[Source: CWC Report, 2001]


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Sediment transport in the

river system

Bank and Shore erosion

Bank and Slope sliding

The silting process of reservoirs is determined by several Natural causes such as:


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Reduction of useful and economic life of reservoirs

The reduction of hydro-power generation, water supply or discharge regulation capacity

Additional lateral force on the dam wall exerted by deposited sediment

Effect due to the action of high velocity, sediment overloaded flows

The abrasion and damage of tunnels, galleries, guiding slots, turbines and other equipment


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Minimize Sediment Entering

Reservoir

Compensate for Sediment

Accumulated in Reservoir

Remove Sediment from Reservoir

Minimize Deposition of Sediment in Reservoir


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Watershed Management: Vegetative Treatment Structural Intervention Operational Measures

Upstream Trapping: Natural vegetation filters,

Check dam, Debris basin, Sediment detention basin, Reservoir.

Locate Reservoir Off-Stream:


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Preserve, Enhance, Restore and Construct wetlands Sediment Control, enhance fish habitat, improve water

quality etc.


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Density currents can form when sediment-laden water from a stream enters the relatively clearer water of a reservoir

The density current then follows down the path of the pre-impoundment river channel

The sediment-laden water can be discharged through low-level outlets (vented).

If the density current is not vented, a “muddy lake” forms near the dam


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The operational technique whereby previously accumulated and deposited sediments in reservoirs are removed by accelerated flows


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Sediment flushing technique is used by two ways:

Drawdown flushing Emptying and Flushing

The flow velocities in the reservoir are increased to such an extent that deposited sediments are remobilized and transported through the low level outlets provided slightly above the original riverbed level with sufficient flow capacity


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Raising the dam Abandon old reservoir and Construction of a new

reservoir Reconstruction of dam wall

New sluicing facilities Changing operation management

Conjunctive management


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Wide Hollow Reservoir:

Location : Northwest of Escalante, Utah

Sedimentation Rate: Average annual loss of 0.91% of original capacity per year (1954-2007) or 48% lost capacity as of 2007.

Management Strategies:

Sediment Basin

Sluice gates installed

Dam Enlargement

Benefit: Restore almost all of the original reservoir capacity.

[Source: Utah State Water Plan, 2010] SEDIMENT CONTROL MEASURES IN RESERVOIR

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Three Gorges Dam: Location : Yangtze River, China Normal Pool Level: 175 m. Flood Season Pool Level: 145 m. Annual Sediment Load: 532 million tons Management Strategies:

During the flood season (June-Sept), when the river carries 90% of the annual sediment load

the pool level is drawn down to flood season pool level (sediment sluicing)

In the upstream the construction of the

and Xiluodu dams trap sediment and reduce the sediment load into the TGP reservoir.

[Source: http://www.iahr.org/uploadedfiles] SEDIMENT CONTROL MEASURES IN RESERVOIR

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Three Gorges Dam

The Xiangjiaba And Xiluodu Dams


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Three Gorges Dam


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Baira Reservoir:

Location: Ravi River in northwest India

Capacity: 3.76 Mm3

Management Strategies:

A 5m x 7m high D shaped diversion tunnel was used for flushing of sediment from the reservoir

Clearing 0.38 Mm3 in 40 hours.

Benefit: Removing an estimated 80 percent of accumulated sediments from the reservoir


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Reservoir sedimentation is a global challenge

The remedial measures presented in this seminar report can prolong the live reservoir capacity

Instead of adopting individual measures these may be adopted in combination for better results.

Considering the alarming rates at which the reservoirs are being silted up, the sediment control practices, measures and works should be adopted


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Gregory L. Morris, Jiahua Fan (2010), “Reservoir sedimentation Handbook”, published by McGraw-Hill.

M Z Qamar, M K Verma, A P Mesharm, M. K. Pawar, Review Of Sediment Control Measures In Reservoirs, India Water Week 2012 – Water, Energy and Food Security: Call for Solutions, 10-14 April 2012, New Delhi.

Managing Sediment in Utah’s Reservoirs, Utah Division of Water Resources, Utah State Water Plan.

SEE Hydropower, Sediment management and reservoir flushing in Austria, Gabriele Harb (Graz University of Technology).

ICOLD. 2004, Draft final report on “Mathematical modelling of sediment transport and deposition in reservoirs” Guidelines and case studies.

Bogdan MARCU, Iulian IANCU, Research on Silting and Desilting Of Reservoirs (Artificial Lakes), U.P.B. Sci. Bull., Series D, Vol. 75, Iss. 2, 2013


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gtu shantilal shah engineering college, bhavnagar...around 40,000 large reservoirs worldwide used...

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