DAM

Prepared by Muneer AhmedDepartment of Water Resources Engineering

Dam is a structure built across a STREAM,RIVER, or estuary to store water. ARESERVOIR is created upstream of the damto supply water for human consumption,IRRIGATION, or industrial use.

Dam is the central structure in a multipurpose schemeaiming at the conservation of water resources.Auxiliary works for a dam include spillways, gates, orvalves to control the discharge of surplus water, anintake structure and means for permitting boats orfishes to cross the dam.

A spillway is a section of a dam designedto pass water from the upstream side ofa dam to the downstream side.Types of spillway include:primary spillway,auxiliary spillway,emergency spillway,fuse plug spillway etc.

Spillways

Flood ControlIrrigationWater StorageMine TailingsDebris ControlWater diversionLand reclamationElectrical GenerationNavigation

Irrigation

Electrical Generation

Land reclamation

Water diversion

Significant considerations when building a daminclude: permeability of the surrounding rock or soilearthquake faultslandslides and slope stabilitywater tablepeak flood flowreservoir siltingenvironmental impacts on river fisheries, forestsimpacts on human habitationscompensation for land being flooded as well aspopulation resettlementremoval of toxic materials and buildings from theproposed reservoir area

Dam erosion

Dam failure

I. By sizeII. By useIII. By structure

Large dams

Major dams

Major dams of the columbia river ecoregion

Major dams on sindhu river , Pakistan

By use dams can be classified as: 1.check dam 2.detention dam 3.diversionary dam 4.dry dam 5.saddle dam 6.storage dam 7.overflow dam 8.wing dam 9.cofferdam

A check damreduces flowvelocity and controlsoil erosion.

Detention dams are constructed to minimize theimpact of flooding and to restrict the flow rate of aparticular channel.

A diversionary dam diverts all or a portion ofthe flow of a river from its natural course.

A dry dam is designed to control flooding. It normally holdsback no water and allows the channel to flow freely, exceptduring periods of intense flow .

Saddle dam under construction A saddle dam is an auxiliary dam constructed to confine the reservoir created by a primary dam.

Storage dams are built to provide a reliable source of waterfor short or long periods of time.

Storage dams

An overflow dam is designed to be over topped.

A weir is a type of small overflow dam that are oftenused within a river channel .

A wing dam extends partway into a river and forces water intoa fast-moving center channel which reduces the rate ofsediment accumulation.

A cofferdam is a (usually temporary) barrier constructedto exclude water from an area that is normally submerged.

By structure dams can beclassified as:1. embankment dam2. timber dam3. arch dam4. gravity dam5. steel dam6. beaver dam

Embankment dams are made from compacted earth,they rely on their weight to hold back the force of water.

The San Luis Dam,California is an embankment dam

A Timber crib dam, MichiganTimber dams were widely used early due to ease and speed ofconstruction. Rarely built in modern times by humans becauseof relatively short lifespan and limited height.

Timber dams

In the arch dam, stability is obtained by acombination of arch and gravity action.

Single arch dam Multiple arch dam

In a gravity dam, stability is secured by making it of such asize and shape that it will resist overturning, sliding andcrushing at the toe.

The Gilboa dam,NY is a solid gravity dam

A steel dam is a type of dam which uses steel plating (at anangle) and load bearing beams as the structure.

Beaver dams are created as a protection against predators,such as coyotes, wolves and bears, and to provide easy accessto food during winter.

Garbage accumulated because of a dam

-> Kaptai Dam-> Rubber dams

Location- on the Karnafuli river at Kaptai in Rangamatidistrict, 65 km upstream of Chittagong.Length- 670.56mHeight- 45.7m highWidth- 45.7m (at foundation level) 7.6m(at crest level)The catchment area of the reservoir- 11,000 sq kmSince it is an earthen dam a 16-gated spillway (each 12.2mby 11.3m) with discharge capacity of 625,000 cusec has beenconstructed on the left side of the main dam.

Kaptai dam

Kaptai dam

Compared to concrete barrage and regulators rubber dams are cheaper and more flexibleand can be fully deflated during the flood season . Rubber dams can be as long as 100mand used for irrigation , small-scale hydropower generation and rural water supply.

Rubber dams in BANGLADESH

Feature Bakkhali Dam Eidgaon DamLength (m) 84 52Height (m) 3.5 3Maximum water retention depth (m) 4 3Maximum overflow discharge (cumec) 256 80Maximum flood flow (cumec) 1073 600Length of concrete floor (m) 40 33.5Protective works (m):Upstream 9 6Downstream 13 8Volume of inflated dam (cu m) 1200 800Weight of dam bag (ton) 14 7Filling pump capacity (cu m/hr) 150 100Filling/emptying time (hr) 8.1 8.1Total cost (million Tk) 36 18

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About hoover damOfficial name- Hoover DamImpounds- Colorado RiverLocale- Nevada-Arizona United StatesLength- 1244 ft (379 m)Height- 726.4 ft (221 m)Construction began- 1931Opening date- 1936Construction cost- $49 million

Hoover dam

Hoover dam

Hoover dam

Aswan dam

Aswan dam

About Nurek dam

Nurek dam

Glen canyon dam

Three Gorges Dam

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