Narrowboat/Canal Boat Hire for Barge Holidays at Barton Turns, Staffordshire, UK        ***Houseboats now also available***
Boat Rental Canal World Forum Find a Holiday Inside the Narrowboats Inside the Houseboats Faq's and Notes Links	Locks   The problems facing the engineers designing the first waterways were: Maintaining depth of water Conserving water Restricting currents within safe limits Prior to the invention of locks water depth could only be maintained by the use of dams, which would then have to be partially broken to allow a boat passage, either with or against a strong current, which would have been dangerous and hard work.  The Pound Lock   The pound lock in many modified forms is the basic solution used to overcome these problems.The lock consists of a central chamber not much longer than the size of the largest boat to be moved, with gates at each end to control the water. Each gate has paddles which can be lifted to allow the lock to be filled or emptied as required.  The usual staring position for using a lock is with both gates closed and all paddles closed. At this stage not water is passing through the lock and the level of the water in the lock is stable.  The water level in the chamber then has to be adjusted to match the level of the canal the boat is floating on prior to entering the lock. If the boat is going downstream this means filling the chamber by lifting paddles in the top (upstream gate). In this instance, with the chamber full, the water level will now match that of the canal filling the lock, with the lower gates now holding back a considerable amount of pressure to maintain the chambers water level above that of the lower canal level. The top gates however can be easily opened to allow the boat to enter the chamber as the water levels either side are balanced. With the boat now in the chamber the top gate is now shut and its paddles closed. The water level in the chamber now has to be reduced to that of the lower canal by opening paddles in the lower gates which drain the chamber. Once water levels are balanced either side of the lower gates the gates can be opened to allow the boat to leave the chamber. At this stage the top gates are maintaining the level of the top canal, thus controlling current, maintaining water depth and conserving water.  A boat moving upstream reverses the process.  Usually excess water in the higher canal is drained off by weirs create a stream that bypasses the lock for water that would otherwise cause the upper canal to flood, though in some cases lock gates are designed so excess water passes straight over the top of them.  Other information: http://dspace.dial.pipex.com/town/square/gd86/locks.htm http://www.canalhttp://www.pigpen.org.uk/locks.htmjunction.com/canal/lock.htm  http://www.pigpen.org.uk/locks.htm