Page 1 :
INTRODUCTION, , A weir is a barrier across the width of a river or stream that alters the, characteristics of the flow and usually results in a change in the height of, the water level. Sharp-crested weirs, commonly referred to as notches, are, manufactured from sharp-edged thin plates., , Definition Of Weir, , Weir is a low obstruction that is built across a river or canal to raise the, water level, or in parallel to divert the water. Two types of weirs are used to, control flow; an in-stream weir and a diversion weir., , What is Weir, , 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., , A weir is a small dam built across a river to control the upstream water, level. Weirs have been used for ages to control the flow of water in streams,, rivers, and other water bodies. Unlike large dams which create reservoirs,, the goal of building a weir across a river isn’t to create storage, but only to, gain some control over the water level. Over time, the term weir has taken, on a more general definition in engineering to apply to any hydraulic control, structure that allows water to flow over its top, often called its crest. In fact,, the spillways of many large dams use weirs as control structures. So how, do they work.
Page 2 :
In many cases, a weir is a passive structure, meaning once it’s installed, there’s no way to change this rating curve. And that’s not always ideal., Streams and river are subject to tremendous variability in flow rate. A, hydraulic structure may normally flow a small amount, but in flooding, conditions be asked to pass incredible volumes of water. With a passive, structure and fixed rating curve, that variability in flow means tremendous, variability in the water level upstream. During a flood, a weir may back up, the water badly enough to cause damage upstream. If you’re using a weir, for the spillway on a dam, you might have to build your dam much higher, just to handle the water level that occurs during very rare but extreme, cases, increasing the overall costs of the structure., , A weir or low head dam is a barrier across the width of a river that alters, the flow characteristics of water and usually results in a change in the, height of the river level. They are also used to control the flow of water for, outlets of lakes, ponds, and reservoirs. There are many weir designs, but, commonly water flows freely over the top of the weir crest before, cascading down to a lower level.
Page 3 :
Type of weir, , 1. Rectangular Weir, , 2. Trangular Weir, , 3. Trapezoidal Weir, , Types of Weirs based on Shape of the Openined, Rectangular weir, , e lItis a standard shape of weir. The top edge of weir may be sharp, crested or narrow crested., , e lItis generally suitable for larger flowing channels., , End View, , , , , , , , , , , , Triangular weir, , e The shape of the weir is actually reverse triangle like V. so, it is also, called V-notch weir., , e This type of weirs are well suitable for measuring discharge over, small flows with greater ccuracy.
Page 4 :
End View, , , , Trapezoidal weir, , e Trapezoidal weir is also called as Cippoletti weir. This is trapezoidal, in shape and is the modification of rectangular weir with slightly, higher capacity for same crest strength., , e The sides are inclined outwards with a slope 1:4 (horizontal : vertical), , End View: Side Slope, ba ATH eb, , , , Importance Of weir, , e Commonly, weirs are used to prevent flooding, measure water, discharge, and help render rivers more navigable by boat., , e Weirs are fixed barriers across a river or stream that force water to, flow over their tops, where the height of the water above the weir can, be used to calculate flow.
Page 5 :
How do weir 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. ... In a weir, the surface over which the water flows is known, as the crest.
