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77-580: The lake has an elevation of 54.9 metres (180 ft) and a surface area of 1.9 square kilometres (0.73 sq mi). The navigable River Havel briefly flows through the Wangnitzsee, both entering and exiting at the west end of the lake. The river enters from a 7.2 kilometres (4.5 mi) channel from Wesenberg and the Woblitzsee , and exiting directly into the Großer Priepertsee . The lake itself

154-419: A fish ladder are often taken to counteract this. Navigation locks have also potential to be operated as fishways to provide increased access for a range of biota. Locks can be built side by side on the same waterway. This is variously called doubling , pairing , or twinning . The Panama Canal has three sets of double locks. Doubling gives advantages in speed, avoiding hold-ups at busy times and increasing

231-555: A boat in a lock. One incident, which took place in June 1873 on the Chesapeake and Ohio Canal, involved the boat the Henry C. Flagg and its drunk captain. That boat was already leaking; the crew, having partially pumped the water out, entered Lock 74, moving in front of another boat. Because they failed to snub the boat, it crashed into and knocked out the downstream gates. The outrush of water from

308-464: A boat in the lock. A 200-ton boat moving at a few miles an hour could destroy the lock gate. To prevent this, a rope was wound around the snubbing post as the boat entered the lock. Pulling on the rope slowed the boat, due to the friction of the rope against the post. A rope 2 + 1 ⁄ 2 inches (6.4 cm) in diameter and about 60 feet (18 meters) long was typically used on the Erie Canal to snub

385-500: A boat travelling upstream, the process is reversed; the boat enters the empty lock, and then the chamber is filled by opening a valve that allows water to enter the chamber from the upper level. The whole operation will usually take between 10 and 20 minutes, depending on the size of the lock and whether the water in the lock was originally set at the boat's level. Boaters approaching a lock are usually pleased to meet another boat coming towards them, because this boat will have just exited

462-528: A broad canal for more than one boat to be in a staircase at the same time, but managing this without waste of water requires expertise. On English canals, a staircase of more than two chambers is usually staffed: the lockkeepers at Bingley (looking after both the "5-rise" and the "3-rise") ensure that there are no untoward events and that boats are moved through as speedily and efficiently as possible. Such expertise permits miracles of boat balletics: boats travelling in opposite directions can pass each other halfway up

539-426: A flight of locks is simply a series of locks in close-enough proximity to be identified as a single group. For many reasons, a flight of locks is preferable to the same number of locks spread more widely: crews are put ashore and picked up once, rather than multiple times; transition involves a concentrated burst of effort, rather than a continually interrupted journey; a lock keeper may be stationed to help crews through

616-412: A gate, or pair of half-gates, traditionally made of oak or elm but now usually made of steel ). The most common arrangement, usually called miter gates , was invented by Leonardo da Vinci sometime around the late 15th century. On the old Erie Canal , there was a danger of injury when operating the paddles: water, on reaching a certain position, would push the paddles with a force which could tear

693-435: A lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock , a boat lift , or on a canal inclined plane , it is the chamber itself (usually then called a caisson ) that rises and falls. Locks are used to make a river more easily navigable, or to allow a canal to cross land that is not level. Later canals used more and larger locks to allow a more direct route to be taken. A pound lock

770-421: A lock. To help boats traveling downstream exit a lock, the locksman would sometimes open the paddles to create a swell, which would help "flush" the boat out of the lock. A boatsman might ask for a back swell, that is, to open and shut the paddles a few times to create some waves, to help him get off the bank where he was stuck. If boats ran aground (from being overloaded) they sometimes asked passing crews to tell

847-430: A short way into the chamber from below the upper gates. Allowing the rear of the boat to "hang" on the cill is the main danger when descending a lock, and the position of the forward edge of the cill is usually marked on the lock side by a white line. The edge of the cill is usually curved, protruding less in the center than at the edges. In some locks, there is a piece of oak about 9 in (23 cm) thick which protects

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924-480: A staircase lock can be used as an emergency dry dock). To avoid these mishaps, it is usual to have the whole staircase empty before starting to descend, or full before starting to ascend, apart from the initial chamber. One striking difference in using a staircase of either type (compared with a single lock, or a flight) is the best sequence for letting boats through. In a single lock (or a flight with room for boats to pass) boats should ideally alternate in direction. In

1001-404: A staircase, however, it is quicker for a boat to follow a previous one going in the same direction. Partly for this reason staircase locks such as Grindley Brook, Foxton, Watford and Bratch are supervised by lockkeepers, at least during the main cruising season, they normally try to alternate as many boats up, followed by down as there are chambers in the flight. As with a flight, it is possible on

1078-516: A stretch of the river. Both routes rejoin in the linked lakes of Breitling See and Plauer See , which leads up to Plaue. Like the preceding stretch of the river, the stretch from Plaue to the confluence with the Elbe at Havelberg is administered as part of the Lower Havel–Waterway. Unlike the previous stretch, this stretch carries considerably less commercial traffic. Vessels heading to or from

1155-454: A swell to anyone to help them on the way, but some would ask for money for the swell. The Erie Canal management did not like swelling for two reasons. First, it used too much water lowering the water on the pound above sometimes causing boats to run aground. In addition, it raised the water level on the pound below, causing some boats to strike bridges or get stuck. On horse-drawn and mule-drawn canals, snubbing posts were used to slow or stop

1232-426: Is a normal top gate, and the intermediate gates are all as tall as the bottom gate). As there is no intermediate pound, a chamber can only be filled by emptying the one above, or emptied by filling the one below: thus the whole staircase has to be full of water (except for the bottom chamber) before a boat starts to ascend, or empty (except for the top chamber) before a boat starts to descend. In an "apparent" staircase

1309-588: Is a right tributary of the Elbe . However, the direct distance from its source to its mouth is only 94 kilometres (58 mi). For much of its length, the Havel is navigable; it provides an important link in the waterway connections between the east and west of Germany, as well as beyond. The source of the Havel is located in the Mecklenburg Lake District , between Lake Müritz and the city of Neubrandenburg . There

1386-626: Is most commonly used on canals and rivers today. A pound lock has a chamber with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock . Pound locks were first used in China during the Song dynasty (960–1279 CE), having been pioneered by the Song politician and naval engineer Qiao Weiyue in 984. They replaced earlier double slipways that had caused trouble and are mentioned by

1463-561: Is navigable to its eastern end, and navigation is administered as part of the Obere–Havel–Wasserstraße . This Mecklenburgische Seenplatte (district) location article is a stub . You can help Misplaced Pages by expanding it . Havel The Havel ( German: [ˈhaːfl̩] ) is a river in northeastern Germany , flowing through the states of Mecklenburg-Vorpommern , Brandenburg , Berlin and Saxony-Anhalt . The 325 kilometres (202 mi) long Havel

1540-623: Is no obvious visible source in the form of a spring, but the river originates in the lakes in the Diekenbruch near Ankershagen , close to and south-east of the watershed between the North and Baltic seas. From there the river initially flows southward, eventually joining the Elbe, which in turn flows into the North Sea. Every river north-east of it flows to the Baltic Sea. The river enters Brandenburg near

1617-443: Is only a staircase if successive lock chambers share a gate (i.e. do not have separate top and bottom gates with a pound between them). Most flights are not staircases, because each chamber is a separate lock (with its own upper and lower gates), there is a navigable pound (however short) between each pair of locks, and the locks are operated in the conventional way. However, some flights include (or consist entirely of) staircases. On

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1694-547: Is placed 11 km downstream. As the course of the Elbe has a higher gradient than the Havel, the water level of the Havel in Havelberg can be kept 1.4 metres below the Elbe (at the junction of the traverse communicating canal, protected by a lock ). Towns along the river include: Fürstenberg , Zehdenick , Oranienburg , Berlin , Potsdam , Werder , Ketzin , Brandenburg , Premnitz , Rathenow and Havelberg. In earlier Greek or Latin sources, such as Tacitus 's Germania ,

1771-846: The Bollène lock on the River Rhône has a fall of at least 23 m (75 ft), the Leerstetten, Eckersmühlen and Hilpoltstein locks on the Rhine–Main–Danube Canal have a fall of 24.67 m (80.9 ft), each and the Oskemen Lock on the Irtysh River in Kazakhstan has a drop of 42 m (138 ft). The natural extension of the flash lock , or staunch, was to provide an upper gate (or pair of gates) to form an intermediate "pound" which

1848-464: The Caledonian Canal the lock gates were operated by man-powered capstans , one connected by chains to open the gate and another to draw it closed. By 1968 these had been replaced by hydraulic power acting through steel rams. The construction of locks (or weirs and dams) on rivers obstructs the passage of fish. Some fish such as lampreys, trout and salmon go upstream to spawn. Measures such as

1925-605: The Elbe Lateral Canal . This stretch of the river descends through locks at Bahnitz , Rathenow , Grütz , Garz and Havelberg . At Rathenow there are two channels, each with a lock. North of Plaue, the river is crossed by the Pritzerbe Ferry . Lock (water transport) A lock is a device used for raising and lowering boats , ships and other watercraft between stretches of water of different levels on river and canal waterways . The distinguishing feature of

2002-470: The Grand Union . Operation of a staircase is more involved than a flight. Inexperienced boaters may find operating staircase locks difficult. The key worries (apart from simply being paralysed with indecision) are either sending down more water than the lower chambers can cope with (flooding the towpath, or sending a wave along the canal) or completely emptying an intermediate chamber (although this shows that

2079-635: The Großes Fenster ( German pronunciation: [ˈɡʁoːsəs ˈfɛnstɐ] ; literally "Great Window") with an unobstructed view upriver, hence the name, followed by the island of Schwanenwerder and the large arm known as the Großer Wannsee . This part of the river can be very busy with leisure craft. The island of Pfaueninsel is also a feature of this stretch of the river. A public ferry crosses these waters between Wannsee and Kladow , carrying passengers and cyclists. The Teltow Canal joins

2156-908: The Müritz–Elde–Wasserstraße . Other connected waterways are the Lychener Gewässer  [ de ] , the Templiner Gewässer  [ de ] and the Wentow Gewässer . The stretch of the river between the junction with the Oder–Havel Canal near Liebenwalde and the confluence with the Spree at Spandau is administered as part of the Havel–Oder–Wasserstraße , which also includes the Oder-Havel Canal. This stretch of

2233-700: The Rochdale Canal , which both have a rise of nearly 20 feet (6.1 m). Both locks are amalgamations of two separate locks, which were combined when the canals were restored to accommodate changes in road crossings. By comparison, the Carrapatelo and Valeira locks on the Douro river in Portugal, which are 279 feet (85 m) long and 39 feet (12 m) wide, have maximum lifts of 115 and 108 feet (35 and 33 m) respectively. The two Ardnacrusha locks near Limerick on

2310-581: The Song dynasty (960–1279 CE). The Songshi or History of the Song Dynasty, volume 307, biography 66, records how Qiao Weiyue, a high-ranking tax administrator, was frustrated at the frequent losses incurred when his grain barges were wrecked on the West River near Huai'an in Jiangsu . The soldiers at one double slipway, he discovered, had plotted with bandits to wreck heavy imperial barges so that they could steal

2387-816: The Templiner See to the Schwielowsee , then northwest to Paretz, whilst the Sacrow–Paretz Canal takes a shorter route due east to Paretz, saving some 13 kilometres (8.1 mi) compared to the 29 kilometres (18 mi) Potsdamer Havel. The Potsdamer Havel is crossed by the Kiewitt Ferry in Potsdam itself, and by the Caputh Ferry at the entrance to the Schweilowsee. At Paretz the two channels join up again, as does

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2464-735: The Useriner See to the Großer Labussee . The stretch of the river between this lock and the junction with the Oder–Havel Canal is administered as part of the Obere–Havel–Wasserstraße , along with various connecting canals and waterways. From Zwenzow downstream to Liebenwalde is a distance of 92 kilometres (57 mi). In this distance the navigation passes through the lakes of Großer Labussee, Woblitzsee , Wangnitzsee , Großer Priepertsee , Ellbogensee , Ziernsee , Röblinsee , Baalensee , Schwedtsee and Stolpsee . It also descends through

2541-466: The Berlin boroughs of Spandau and Reinickendorf respectively. The last 10 kilometres (6 mi) of this stretch of the river, from Hennigsdorf, passes through a series of interconnected lakes, including the large Tegeler See . The river enters Berlin 6 kilometres (4 mi) before Spandau, having formed the boundary for the previous 4 kilometres (2.5 mi). During the partition of Germany , this formed

2618-510: The Chinese polymath Shen Kuo (1031–1095) in his book Dream Pool Essays (published in 1088), and fully described in the Chinese historical text Song Shi (compiled in 1345): The distance between the two locks was rather more than 50 paces, and the whole space was covered with a great roof like a shed. The gates were 'hanging gates'; when they were closed the water accumulated like a tide until

2695-608: The German commercial waterway network, carrying traffic from the Rhine and the North Sea to Berlin and Poland . From a navigation perspective, the Havel can be split into four sections with somewhat different characteristics and different administrative arrangements. The Havel is navigable to canoes and similar small craft from close to its source. Motor craft are prohibited above the first lock at Zwenzow  [ de ] , which links

2772-552: The Grand Union (Leicester) Canal, the Watford flight consists of a four-chamber staircase and three separate locks; and the Foxton flight consists entirely of two adjacent 5-chamber staircases. Where a very steep gradient has to be climbed, a lock staircase is used. There are two types of staircase, "real" and "apparent". A "real" staircase can be thought of as a "compressed" flight, where

2849-580: The Havel Canal from further upstream. Just downstream of Paretz, the river is crossed by the Ketzin Cable Ferry . At Brandenburg an der Havel, the navigation again splits into two routes. Commercial shipping descends through a lock into the Silo Canal that passes to the north of the city centre. Leisure craft pass through the centre of the city, using the short Brandenburg City Canal , a smaller lock, then

2926-506: The Havel downstream, and was built in the 1950s to allow East German vessels to avoid the stretch of the river under the political control of West Berlin . Some 7 kilometres (4.3 mi) further downstream, the Berlin-Spandau Ship Canal joins the river on the east bank, providing a connection to central Berlin without passing through the lock at Spandau. A car ferry crosses the river between Hakenfelde and Konradshöhe , in

3003-644: The Rhine and the west of Germany take the Elbe–Havel Canal at Plaue. Whilst the lower reaches of the Havel provide the most direct route to Hamburg and the North Sea ports, variable water levels in the Elbe affect those in the lower Havel; together these can restrict navigation. A less direct, but more reliable route is available via the Elbe–Havel Canal, the Magdeburg Water Bridge , the Mittelland Canal and

3080-512: The Shannon navigation in Ireland have a rise of 100 feet (30 m). The upper chamber rises 60 feet (18 m) and is connected to the lower chamber by a tunnel, which when descending does not become visible until the chamber is nearly empty. A pound is the level stretch of water between two locks (also known as a reach ). The cill , also spelled sill , is a narrow horizontal ledge protruding

3157-470: The advent of canals in Britain. The sides of the turf-lock are sloping so, when full, the lock is quite wide. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. On British canals and waterways most turf-sided locks have been subsequently rebuilt in brick or stone, and so only a few good examples survive, such as at Garston Lock , and Monkey Marsh Lock , on

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3234-545: The border between East Germany and West Berlin, and border control points were established for vessels navigating the river. The stretch of the river between the confluence with the Spree at Spandau and the junction with the Elbe–Havel Canal at Plaue is administered as part of the Lower Havel–Waterway , which also includes the stretch of river downstream to the confluence with the Elbe. Between Spandau and Plaue,

3311-463: The bottom cill at all but the higher tides – the new bottom chamber rises just far enough to get the boat over the original lock cill. In China, the recently completed Three Gorges Dam includes a double five-step staircase for large ships, and a ship lift for vessels of less than 3000 metric tons. Examples of "apparent" staircases are Foxton Locks and Watford Locks on the Leicester Branch of

3388-617: The canal would cause frequent interruptions of the heavy road traffic. It can be emptied by pumping – but as this uses a lot of electricity the method used when water supplies are adequate is to drain the lock to a nearby burn . In 2016 the Kieldrecht Lock in the Port of Antwerp in Belgium took over the title of the world's largest lock from the Berendrecht Lock in the same port and still has

3465-588: The chambers so that some water from the emptying chamber helps to fill the other. This facility has long been withdrawn on the English canals, although the disused paddle gear can sometimes be seen, as at Hillmorton on the Oxford Canal . Elsewhere they are still in use; a pair of twinned locks was opened in 2014 on the Dortmund–Ems Canal near Münster , Germany. The once-famous staircase at Lockport, New York ,

3542-617: The chambers still have common gates, but the water does not pass directly from one chamber to the next, going instead via side ponds. This means it is not necessary to ensure that the flight is full or empty before starting. Examples of famous "real" staircases in England are Bingley and Grindley Brook . Two-rise staircases are more common: Snakeholme Lock and Struncheon Hill Lock on the Driffield Navigation were converted to staircase locks after low water levels hindered navigation over

3619-404: The chance of a boat finding a lock set in its favour. There can also be water savings: the locks may be of different sizes, so that a small boat does not need to empty a large lock; or each lock may be able to act as a side pond (water-saving basin) for the other. In this latter case, the word used is usually "twinned": here indicating the possibility of saving water by synchronising the operation of

3696-514: The concept has been suggested in a number of cases, the only example in the world of a drop lock that has actually been constructed is at Dalmuir on the Forth and Clyde Canal in Scotland. This lock, of the single-chamber type, was incorporated during the restoration of the canal, to allow the replacement of a swing bridge (on a busy A road) by a fixed bridge, and so answer criticisms that the restoration of

3773-448: The first to solve the problem of keeping the Nile free of salt water when his engineers invented the lock around 274/273 BC. All pound locks have three elements: The principle of operating a lock is simple. For instance, if a boat travelling downstream finds the lock already full of water: If the lock were empty, the boat would have had to wait 5 to 10 minutes while the lock was filled. For

3850-599: The first true pound lock was built in 1396 at Damme near Bruges , Belgium. The Italian Bertola da Novate (c. 1410–1475) constructed 18 pound locks on the Naviglio di Bereguardo (part of the Milan canal system sponsored by Francesco Sforza ) between 1452 and 1458. In Ancient Egypt, the river-locks was probably part of the Canal of the Pharaohs : Ptolemy II is credited by some for being

3927-425: The flight quickly; and where water is in short supply, a single pump can recycle water to the top of the whole flight. The need for a flight may be determined purely by the lie of the land, but it is possible to group locks purposely into flights by using cuttings or embankments to "postpone" the height change. Examples: Caen Hill locks, Devizes . "Flight" is not synonymous with "Staircase" (see below). A set of locks

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4004-512: The form of the now-disused Écluse des Lorraines , connecting the Canal latéral à la Loire with the River Allier . A drop lock can consist of two conventional lock chambers leading to a sump pound, or a single long chamber incorporating the sump – although the term properly applies only to the second case. As the pounds at either end of the structure are at the same height, the lock can only be emptied either by allowing water to run to waste from

4081-516: The inside walls of the lock with wood, so as not to abrade the boats. This was done, for instance, on the Chesapeake and Ohio Canal with the locks near the Paw Paw Tunnel . and also the Chenango Canal On large modern canals, especially very large ones such as ship canals , the gates and paddles are too large to be hand operated, and are operated by hydraulic or electrical equipment. On

4158-414: The intermediate pounds have disappeared, and the upper gate of one lock is also the lower gate of the one above it. However, it is incorrect to use the terms staircase and flight interchangeably: because of the absence of intermediate pounds, operating a staircase is very different from operating a flight. It can be more useful to think of a staircase as a single lock with intermediate levels (the top gate

4235-450: The lock caused the upstream gates to slam shut, breaking them also, and sending a cascade of water over the boat, sinking it. This suspended navigation on the canal for 48 hours until the lock gates could be replaced and the boat removed from the lock. To economise, especially where good stone would be prohibitively expensive or difficult to obtain, composite locks were made, i.e. they were constructed using rubble or inferior stone, dressing

4312-413: The lock on their level and therefore set the lock in their favour – saving about 5 to 10 minutes. However, this is not true for staircase locks, where it is quicker for boats to go through in convoy, and it also uses less water. The rise is the change in water-level in the lock. The two deepest locks on the English canal system are Bath deep lock on the Kennet and Avon Canal and Tuel Lane Lock on

4389-403: The locks at Wesenberg , Steinhavelmühle , Fürstenberg, Bredereiche , Regow , Zaaren , Schorfheide , Zehdenick , Bischofswerder and Liebenwalde . The Woblitzsee also gives access to the Kammer Canal , which allows vessels to reach Neustrelitz . The Ellbogensee links to the Müritz–Havel–Wasserstraße , which proceeds deeper into the Mecklenburg Lake District, eventually connecting with

4466-492: The lower Rhine. At the southern end of the Ruppiner See , weirs can distribute the waters of the Rhin either east- or westwards, rejoining the Havel in two places 67 kilometres (42 mi) apart along a straight line, and more than 160 kilometres (99 mi) apart along the course of the river. The region around and north of the middle Havel is called the Havelland . It consists of sandy heights, sometimes called Ländchen , and low marshes, called luchs . A few kilometres of

4543-516: The name of the river was also written as Habola, Habula, Havela . The river name Havel is related to German Haff, habe, hafen , MHG Hafen meaning port, harbor). The Slavic people who later moved into the Havel area were referred to in German sources as Heveller (occasionally as Havolane ). The Havel is navigable from the Mecklenburg Lake District to its confluence with the Elbe . Whilst its upper reaches carry little other than leisure traffic, further downstream it provides an important link in

4620-419: The new canal was low. This resulted in a sequential pair of locks, with gates pointing in opposite directions: one example was at Hall Green near Kidsgrove , where the southern terminus of the Macclesfield Canal joined the Hall Green Branch of the earlier Trent and Mersey Canal . The four gate stop lock near Kings Norton Junction, between the Stratford-upon-Avon Canal and the Worcester and Birmingham Canal

4697-408: The required level was reached, and then when the time came it was allowed to flow out. The water level could differ by 4 or 5 feet (1.2 or 1.5 m) at each lock and in the Grand Canal the level was raised in this way by 138 feet (42 m). In medieval Europe a sort of pound lock was built in 1373 at Vreeswijk , Netherlands. This pound lock serviced many ships at once in a large basin . Yet

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4774-426: The river before its confluence with the Elbe near Havelberg are in the State of Saxony-Anhalt. Due to its minimal gradient it is susceptible to high waters in the Elbe. Unless in extreme floods, if the dike of the Elbe is submerged, the discharge of the Havel is improved by the Gnevsdorfer Vorfluter (something like "Gnevsdorfer outfall"). By this canal, the mouth of the Havel, that naturally would be near Havelberg,

4851-435: The river forms part of the main inland waterway route from Germany to Poland and carries significant commercial traffic. This stretch of the river is 40 kilometres (25 mi) long, and the river descends through two locks at Lehnitz  [ de ] and Spandau. At Hennigsdorf , 30 kilometres (19 mi) downstream of Liebenwalde, the Havel Canal joins the river on the west bank. This canal connects to Paretz , on

4928-418: The river forms part of the main inland waterway route from the Rhine and the west of Germany; from Hamburg and the North Sea ports, to both Berlin and Poland. It thus carries a considerable amount of commercial traffic. South of Spandau, the river widens into a wide lake that extends, through some narrower areas, to Potsdam. On the east bank south of Spandau is the Grunewald with several beaches, among them

5005-431: The river from the east via the Griebnitzsee just before the city reaches the city of Potsdam, providing an alternative route to the Oder–Spree Canal avoiding central Berlin. The Griebnitz Canal provides a short cut for smaller vessels from the Griebnitzsee to the Großer Wannsee. At Potsdam the navigation splits into two channels. The Havel, here known as the Potsdamer Havel, takes a route southwest through Potsdam and

5082-404: The solid part of the lock cill. On the Oxford Canal it is called a babbie; on the Grand Union Canal it is referred to as the cill bumper. Some canal operation authorities, primarily in the United States and Canada, call the ledge a miter sill (mitre sill in Canada). Gates are the watertight doors which seal off the chamber from the upper and lower pounds. Each end of the chamber is equipped with

5159-407: The spilled grain. In 984 Qiao installed a pair of sluice-gates two hundred and fifty feet apart, the entire structure roofed over like a building. By siting two staunch gates so close to one another, Qiao had created a short stretch of canal, effectively a pound-lock, filled from the canal above by raising individual wooden baulks in the top gate and emptied into the canal below by lowering baulks in

5236-411: The staircase by moving sideways around each other; or at peak times, one can have all the chambers full simultaneously with boats travelling in the same direction. When variable conditions meant that a higher water level in the new canal could not be guaranteed, then the older company would also build a stop lock (under its own control, with gates pointing towards its own canal) which could be closed when

5313-413: The sump to a lower stream or drain, or (less wastefully) by pumping water back up to the canal. Particularly in the two-chamber type, there would be a need for a bypass culvert, to allow water to move along the interrupted pound and so supply locks further down the canal. In the case of the single-chamber type, this can be achieved by keeping the lock full and leaving the gates open while not in use. While

5390-438: The title for largest volume. In 2022 the IJmuiden sea lock serving the Port of Amsterdam became the world's largest lock by surface area. The lock is 500 m (1,600 ft) long, 70 m (230 ft) wide and has sliding lock gates creating a usable depth of 18 m (59 ft). The size of locks cannot be compared without considering the difference in water level that they are designed to operate under. For example,

5467-400: The top gate and raising ones in the lower. A turf-sided lock is an early form of canal lock design that uses earth banks to form the lock chamber, subsequently attracting grasses and other vegetation, instead of the now more familiar and widespread brick, stone, or concrete lock wall constructions. This early lock design was most often used on river navigations in the early 18th century before

5544-601: The town of Fürstenberg . In its upper course and between Berlin and Brandenburg an der Havel the river forms several lakes. The Havel's main tributary is the Spree , which joins the Havel in Spandau , a western borough of Berlin, and is longer and delivers more water than the Havel itself above the confluence. The second largest tributary is the Rhin , named in the Middle Ages by settlers from

5621-404: The upstream lock to give them an extra heavy swell, which consisted of opening all the paddles on the lock gate, creating a surge that affected the whole pound below. On the Erie Canal, some loaded boats needed a swell to get out of the lock. Particularly lumber boats, being top heavy, would list to one side and get stuck in the lock, and needed a swell to get them out. Some lockkeepers would give

5698-405: The windlass (or handle) out of one's hands, or if one was standing in the wrong place, could knock one into the canal, leading to injuries and drownings. On the Chesapeake and Ohio Canal, the lockkeepers were required to remove the windlasses from all lock paddles at night, to prevent unauthorized use. A swell was caused by opening suddenly the paddle valves in the lock gates, or when emptying

5775-456: Was all that need be emptied when a boat passed through. This type of lock, called a pound lock was known in Imperial China and ancient Europe and was used by Greek engineers in the Canal of the Pharaohs under Ptolemy II (284 to 246 BC), when engineers solved the problem of overcoming the difference in height through canal locks . Pound locks were first used in medieval China during

5852-416: Was also a doubled set of locks. Five twinned locks allowed east- and west-bound boats to climb or descend the 60 feet (18 m) Niagara Escarpment , a considerable engineering feat in the nineteenth century. While Lockport today has two large steel locks, half of the old twin stair acts as an emergency spillway and can still be seen, with the original lock gates having been restored in early 2016. Loosely,

5929-588: Was replaced in 1914 by a pair of guillotine lock gates which stopped the water flow regardless of which canal was higher. These gates have been permanently open since nationalisation. The best known example of a round lock is the Agde Round Lock on the Canal du Midi in France. This serves as a lock on the main line of the canal and allows access to the Hérault River . A second French round lock can be found in

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