A sluice gate is a mechanism used to control water flow. These devices are often used in water treatment plants, mining, dams, rice fields, and cranberry bogs, among other places. The gates are typically made of wood or metal, and often slide vertically on a frame to open or close, allowing water to flow out of a space or to be contained in it. For this reason, they are also known as a sluice gate valve.
Sluice gate design is not only limited to a vertical sliding system, however. One kind of sluice gate acts like a flap and is moved by water pressure being greater on one side than the other. Others are even cylindrical in nature.
The word sluice indicates a man-made channel or modified natural waterway that conducts water. This kind of gate regulates how and where that water is moved. This is especially useful for controlling flooding or water levels in farming and other industries.
Many sluice gates are moved by means of a threaded rod system, which needs to be regularly cleaned and greased. Often, when these gates are used in applications with a large amount of water pressure, such as dams, they are raised and lowered by hydraulic systems to control the sluice gate flow. Sometimes in smaller uses, such as in cranberry bogs, the gates are raised and lowered manually. At other times, an electrically-driven hoisting system is used.
Historically, sluice gates proved useful in mills. A mill sluice was known as a millrace, and would often turn a waterwheel or turbine, which could be then used to power equipment needed in sawmills and gristmills. The millrace was often regulated by sluice gates to decrease or increase the flow of water, depending on when it was needed.
A sluice gate can be known by other names depending on geographic location. For example, in the coastal plains of Sommerset, England, the gates are known as clyce or clyse. In Guyana, they are referred to as kokers.
One concern with the use of sluice gates in rice fields is that fish often cannot navigate through them. In Bangladesh, for instance, much of the flood plain is used to grow rice, and water level is regulated for its optimal growth. Since sluice gates have been used for this, fish became scarce where they were once plentiful. Traditionally, the fish have formed an important part of the diet of the poor who inhabit the region. Once the problem was recognized, guidelines were established for gate use, ensuring that fish can travel where they need to so that local fishing remains viable.