Re: Kolhapur Type Weir Pdf Download
Rocki Stenger
The 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 sharp edge prevents the nappe from adhering to the crest. Knife edges should be avoided because they are difficult to maintain.
Height and length of KT weir: 30m 3m. Length: 1000m and therefore volume: 100,000 cubic meter, i.e., 0.1MCM. At 10cm watering, we get 100 hectares of irrigation. About 30-40km of river gives us 4MCM per discharge.11-Oct-2015
Barrages are built near cities so that the amount of water flowing in the river can be controlled by opening and closing the gates to save the city from flooding. A weir, in contrast, is built, for example, in tourist destinations and preservation areas to allow the fish to swim upstream.
The discharge coefficients of the studied weirs were also investigated, and it was concluded that B-Type weir has better performance than other weirs. On average, the discharge coefficient of B-Type weir was 9.9%, 21.2%, and 24.1% higher than that of A-Type, C-Type, and D-Type weir, respectively.19-Sept-2020
There should be air (not trapped) underneath the water leaving the weir. The Length is the bottom width of the weir. The height is measured from the bottom of the weir opening to the top of the water level ponded behind the weir (not the water level right as it leaves the weir).
Thus, weirs are partially classified as rectangular, trapezoidal, triangular, etc. In the case of sharp weirs, the triangular weir is also called a V-notch weir, and one kind of trapezoidal weir is the Cipoletti weir.
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.15-Feb-2018
Unfortunately, weirs don't offer the same luxury, as maintenance requirements are fairly extensive in comparison. The weir crest must be checked often for any nicks or other kinds of damages. Additionally, users must make sure that there's no debris or growth altering the dimensions of the crest.
Weirs are commonly used to control the flow rates of rivers during periods of high discharge. Sluice gates (or in some cases the height of the weir crest) can be altered to increase or decrease the volume of water flowing downstream.
A weir is an impervious barrier constructed across a river to raise the water level on the upstream side. The water is raised up to the required height and the water then flows over the weir. In a weir the water overflows the weir, but in a dam the water overflows through a special place called a spillway.
Though dams and weirs are similar structures that help in controlling the flow of water across a river, dams are considerably large and high while weirs are small. Water collected behind the walls of both dam and weir is used for agriculture and drinking water supply.19-Jun-2011
Without additional flow conditioning, weirs can require long upstream weir pools - the greater the weir hear head, the greater the length of the weir pool. Weir pools should be straight and of constant dimension for at least 20 times the maximum head (Hmax) over the weir.
Similarly the width of the channel can be a concern. Unless the weir chosen is a rectangular weir without end contractions, there should be at least 2 Hmax to each side of the widest wetted portion of the notch. Narrower than this and the approaching flow with have a higher velocity than normal for the weir - resulting in indicated flow rates that are lower than the actual flow rates. As before, V notch the widest channel, then Cipolletti, then rectangular weirs with end contractions, and finally rectangular weirs without end contractions.
If a rectangular weir without end contractions is selected as the weir type, the channel banks must be such that they can allow for breather tubes to be installed at both banks. These tubes allow air to circulate between the downstream face of the weir plate and the underside of the nappe (body of water passing over the weir crest).
A high-level delegation of irrigation engineers from Telangana is expected to be in Aurangabad, Maharashtra, on Monday as part of their two-day study of KT (Kolhapur-Type) weir technology, popularly known as bridge-cum-barrage, implemented on a large-scale in the neighbouring State to tap river waters in small quantities at multiple places.
Kolhapur type (K.T.) weir gates made of FRP are used for storage of water in weirs. FRP gates can operate only up to five meter water head. It is sandwich structure of FRP skin with M.S. structure baking. Water side is covered by FRP skin plate. Maintenance will be less and life of gate will be more.
A weir /wɪər/ 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. Weirs 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. There is no single definition as to what constitutes a weir, and one English dictionary simply defines a weir as a small dam.
The word likely originated from Middle English were, Old English wer, a derivative of the root of the verb werian, meaning "to defend, dam".[1][2] The German cognate is Wehr, which means the same as English weir.
Commonly, weirs are used to prevent flooding, measure water discharge, and help render rivers more navigable by boat. In some locations, the terms dam and weir are synonymous, but normally there is a clear distinction made between the structures. Usually, a dam is designed specifically to impound water behind a wall, whilst a weir is designed to alter the river flow characteristics.
A common distinction between dams and weirs is that water flows over the top (crest) of a weir or underneath it for at least some of its length. Accordingly, the crest of an overflow spillway on a large dam may therefore be referred to as a weir. Weirs can vary in size both horizontally and vertically, with the smallest being only a few centimetres in height whilst the largest may be many metres tall and hundreds of metres long. Some common weir purposes are outlined below.
Weirs allow hydrologists and engineers a simple method of measuring the volumetric flow rate in small to medium-sized streams/rivers or in industrial discharge locations. Since the geometry of the top of the weir is known and all water flows over the weir, the depth of water behind the weir can be converted to a rate of flow. However, this can only be achieved in locations where all water flows over the top of the weir crest (as opposed to around the sides or through conduits or sluices) and at locations where the water that flows over the crest is carried away from the structure. If these conditions are not met, it can make flow measurement complicated, inaccurate, or even impossible.
However, this calculation is a generic relationship and specific calculations are available for the many different types of weir. Flow measurement weirs must be well maintained if they are to remain accurate.[3][4]
As weirs are a physical barrier, they can impede the longitudinal movement of fish and other animals up and down a river. This can have a negative effect on fish species that migrate as part of their breeding cycle (e.g., salmonids), but it also can be useful as a method of preventing invasive species moving upstream. For example, weirs in the Great Lakes region have helped to prevent invasive sea lamprey from colonising farther upstream.
Mill ponds are created by a weir that impounds water that then flows over the structure. The energy created by the change in height of the water can then be used to power waterwheels and power sawmills, grinding wheels, and other equipment.
Weirs are commonly used to control the flow rates of rivers during periods of high discharge. Sluice gates (or in some cases the height of the weir crest) can be altered to increase or decrease the volume of water flowing downstream. Weirs for this purpose are commonly found upstream of towns and villages and can either be automated or manually operated. By slowing the rate at which water moves downstream even slightly, a disproportionate effect can be had on the likelihood of flooding. On larger rivers, a weir can also alter the flow characteristics of the waterway to the point that vessels are able to navigate areas previously inaccessible due to extreme currents or eddies. Many larger weirs will have construction features that allow boats and river users to "shoot the weir" and navigate by passing up or down stream without having to exit the river. Weirs constructed for this purpose are especially common on the River Thames, and most are situated near each of the river's 45 locks.
Because a weir impounds water behind it and alters the flow regime of the river, it can have an effect on the local ecology. Typically, the reduced river velocity upstream can lead to increased siltation (deposition of fine particles of silt and clay on the river bottom) that reduces the water oxygen content and smothers invertebrate habitat and fish spawning sites. The oxygen content typically returns to normal once water has passed over the weir crest (although it can be hyper-oxygenated), although increased river velocity can scour the river bed causing erosion and habitat loss.
Weirs can have a significant effect on fish migration.[6] Any weir that exceeds either the maximum height a species can jump or creates flow conditions that cannot be bypassed (e.g., due to excessive water velocity) effectively limits the maximum point upstream that fish can migrate. In some cases this can mean that huge lengths of breeding habitat are lost, and over time this can have a significant impact on fish populations.
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