TYPES OF DAMS,HYDRAULIC STRUCTURES

&POWER PLANTS

A dam is a hydraulic structure of impervious

material built across a river or stream to create a reservoir on its upstream side for storing water for various purposes.

These purposes may be irrigation, hydro-power, water-supply, flood control, navigation, fishing and recreation.

DAM:

STRUCTURE OF DAM :

Dams are classified on the basis of following types:

By structure By material

TYPES OF DAMS:

Arch dams Gravity dams Arch – Gravity dams Embankment dams

BY STRUCTURE:

Situated at narrow canyon with steep side walls

Constant angle dams are more common than constant radius

Double curvature Require good rock

foundation

ARCH DAMS:

Force that holds dam is earth’s gravity pulling down on mass of dam

Well suited for blocking rivers in wide valleys

Dam is made from concrete or masonry or both

Foundation must have high bearing strength

GRAVITY DAMS:

It has characteristics of arch dam and gravity dam

They are made up of conventional concrete or RCC or masonry

It is thinner than pure gravity dams and require less internal fill

ARCH-GRAVITY DAMS:

Special kind of dam which consist of a line of large gates that can be opened or closed to control the amount of water

Built at mouth of rivers and often used to control water flow for irrigation system

BARRAGES:

These are embankments

of compact granular soil in combination with impervious areas

If clay is used then it is composite dam

These dams are resistant to damage from earthquakes

ROCKFILL DAMS:

They are generally made up of one type of material

Earthen dams can be constructed from materials found on site or nearby

They are cost effective

EARTH FILL DAMS:

STEEL DAMS TIMBER DAMS

BY MATERIAL:

STEEL DAM•Steel dam is a type of dam that is made of steel, rather than common masonry ,earthworks , concrete or construction material •Steel dams - an experiment which failed•Maintenance cost is high due to rust and corrosion

Advantages and Disadvantages

• Principle of operation

Timber dams were widely used in early part of industrial revolution and rarely used now

Suitable location for construction

In order to maintain water retension property they must be kept wet

TIMBER DAM

Cofferdam : a barrier usually temporary, constructed to exclude water from area that is normally submerged

Natural dams : created by natural geological forces. Volcanic dams are formed when erupted lava intercept path of a stream. Natural disasters like earthquake and landslides frequently create landslide dams in mountainous region. Eg. Usoi dam in Tajikistan

Some other types of dams:

Hydroelectricity• Hydroelectricity is the term referring to

electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water.

• It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation 3,427 terawatt-hours of electricity production in 2010.

• Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer.

• The theory is to build a dam on a large river that has a large drop in elevation .

• The dam stores lots of water behind it in the reservoir.• Near the bottom of the dam wall there is the water intake.

Gravity causes it to fall through the penstock inside the dam.

• At the end of the penstock there is a turbine propeller, which is turned by the moving water. • The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to user .

WORKING PRINCIPLE

Pumped storage: Reusing water for peak electricity

demand Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up at storage pool above the powerplant.

An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output.

Disadvantages of big Hydroelectricity plant

• Ecosystem damage and loss of land

• Siltation and flow shortage

• Relocation of local people

• Failure risks