Tidal Gates

C. Evaporation. Seawater collected in a pond is allowed to sit and evaporate. Tidal gates, which are always closed during low tide to prevent backflow of brine, can be kept closed to prevent dilution until a certain amount of water has evaporated and the partly evaporated brine has been transferred to another pond. Alternatively, seawater can be allowed to enter the first pond along with the tides in order to keep the front-end productivity at a maximum. 

Chapter 16 contains case studies relating to tidal gates. 

Gates and turbines are installed along the dam. When the tides produce an adequate difference in the level of the water on opposite sides of the dam, the water flows through the turbines that turn an electric generator to produce electricity. Tidal fences can also harness the energy of tides. They can be used in areas such as channels between two landmasses. Tidal fences... 

To provide steady flow of seawater through the recovery beds during the twice-daily change of tides, an elaborate system of tidal basins, dikes, and sea gates is required, responsible for two-thirds of the plant s high cost. 

Leizhou Bay is a semi-enclosed bay and there are many deep grooves in the bay, so tidal current in the bay is restricted by shoreline shape and underwater topography, and flow reciprocally along the deep grooves (see Fig. 8). During flood tide, the most part of tide prism enters the bay from the gate at south of Naozhou Island, with flow direction from SE to NW the other part of tide prism enters the bay from Naozhou Channel with flow direction from NE to SW. During ebb tide, the flow direction is the opposite. At southeastern bay, tidal current flows reciprocally with direction from SE to NW, and at central bay, tidal current flows reciprocally with direction from E to W. 

Existing Water Controls. In some waterways, controlling the flow of water can confine heavier-than-water spills. Tidal streams can simply be diked. Waterways used for irrigation may have a system of diversion gates that can be closed or a pumping system that can be shut down. Typically, streams, creeks, and rivers are not controlled and require a different approach. 

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