Why Do We Use Weir?

How do locks and weirs work?

The purpose of the weirs is to: …

store water for consumptive use and to regulate river flow downstream.

provide a raised river level upstream of the weir to improve the navigability of the river (vessels can navigate through the weir via its lock)..

How does a weir measure flow?

Weirs to Measure Flow It works by raising the water level upstream of the weir, and then forcing the water to spill over. The more water is flowing over the weir, the deeper the water will be upstream of the weir. So measuring flow rate (CFS) can be done by simply measuring the depth of the water upstream.

What is Surplus Weir?

SURPLUS WEIR. • The surplus work of a reservoir or tank is usually a Weir. • The length of such a weir must be such that the quantity of water.

What is a drowning machine?

“Drowning Machine” is the term used to describe the dangerous situation that is cre- ated when water flows over a low-head dam. As the stream of water flows over the dam it drops into the water below creating a back- wash or a current.

What does Weir mean?

(Entry 1 of 2) 1 : a fence or enclosure set in a waterway for taking fish. 2 : a dam in a stream or river to raise the water level or divert its flow.

Why are weirs so dangerous?

Why are weirs dangerous? After heavy rain, an overflowing weir can become a drowning machine due to the volume of water flowing over the person underwater, making self-rescue, and even assisted rescue, almost impossible. … Being a good swimmer has nothing to do with survival once you are trapped in the drowning machine.

What is a Cipolletti Weir?

Cipoletti Weir. A standard Cipoletti weir is trapezoidal in shape. The crest and sides of the weir plate are placed far enough from the bottom and sides of the approach channel to produce full contraction. The sides incline outwardly at a slope of 1 horizontal to 4 vertical.

What is a low dam?

A low-head head dam is a structure that generally spans from one side of a riverbank to the other, partially blocking the waterway and creating a back-up of water behind the dam. … Low-head dams can be found in rivers and streams across the country.

What are low head dams used for?

They regulate fluctuations in the depth of the river upstream. Low-head dams are typically used to impound water for hydropower, mill ponds, irrigation, water supply, navigation, and recreation. When water flows over a low-head dam, it forms a hydraulic jump or intense recirculation of the water below the dam.

For what purpose dams were traditionally built?

Dams were traditionally built to impound rivers and rainwater that could be used later to irrigate agricultural fields. Today, dams are built not just for irrigation but for electricity generation, water supply for domestic and industrial uses, flood control, recreation, inland navigation and fish breeding.

Where are weirs used?

Weirs have traditionally been used to create mill ponds. They are also used to prevent flooding, measure discharge, and help render a river navigable. The crest of an overflow spillway on a large dam is often called a weir. Weirs can be built of wood, concrete or moraine material (rocks, gravel, boulders).

What is Weir coefficient?

The weir coefficient (as shown above in the weir equation) is a lumped parameter that includes the discharge coefficient, the gravitational constant, and constants based on geometric properties.

What is difference between dam and barrage?

Terminology. According to the World Commission on Dams, a key difference between a barrage and a dam is that a dam is built for water storage in a reservoir, which raises the level of water significantly. … Barrages are usually larger than the headworks of irrigation and navigation canals, with which they are associated.

What is Weir length?

A contracted weir means that the ditch leading up to the weir is wider than the weir opening itself. The length is found by measuring the bottom width of the weir and the height is determined from measuring the water height above the bottom of the weir. Length: ft.

What is Weir Engineering?

A weir is a concrete or masonry structure which is constructed across the open channel (such as a river) to change its water flow characteristics. Weirs are constructed as an obstruction to flow of water. These are commonly used to measure the volumetric rate of water flow, prevent flooding and make rivers navigable.

How do Weirs work?

A weir is a small barrier built across a stream or river to raise the water level slightly on the upstream side; essentially a small-scale dam. Weirs allow water to pool behind them, while allowing water to flow steadily over top of the weir.

How do you create a weir?

Criteria for Proper Weir DesignThe weir should consist of a thin plate 1/8 to 1/4 inch (3 to 6 mm) thick with a straight edge or a thicker plate with downstream chamfered edge. … The upstream face of the weir should be smooth and perpendicular to the axis of the channel in both horizontal and vertical directions.More items…•

What does spillway mean?

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically the riverbed of the dammed river itself. … Spillways ensure that the water does not overflow and damage or destroy the dam.

What is triangular Weir?

Description. Triangular weirs are sharp crested thin plates with V-shaped opening (or notch). These plates are installed at the exit of a channel, tank, or basin in order to measure the real-time flow of water. For a given weir profile size and shape, the flow of water is related to the head of water at the weir.

What is hydraulic jump in fluid mechanics?

Introduction. A hydraulic jump is a fluid shockwave created at the transition between laminar and turbulent flow. … Friction against the sink surface slows the flow until an abrupt change occurs. At this point, the depth increases as water piles up in the transition region and flow becomes turbulent [1].