6.2. Common Spillway Gate Types

Radial/Tainter Gates: Curved, rotate about a trunnion; commonly used for large flows.

Radial gates, also known as Tainter gates, have a curved shape and are designed to rotate around a hinge point, called a trunnion. This design allows them to effectively manage large volumes of water, making them ideal for main spillways in large dams. When the gate is opened, it allows water to flow through a channel, reducing pressure on the dam structure.

Think of a radial gate like a large teeter-totter - when one side is lifted, the other side goes down, allowing water to spill over. Just as a teeter-totter can lift someone up and let them down gently, radial gates control water releases from dams safely.

Sluice Gates: Slide up/down; control entry/exit flow.

Sluice gates are designed to slide vertically or horizontally to control the flow of water entering and exiting a reservoir or spillway. They are commonly used for moderate flows, allowing operators to adjust water levels precisely, either to fill a reservoir or to release excess water when needed.

Imagine using a sliding door in your home. When you slide it open, fresh air comes in or you can let it out. Similarly, sluice gates slide up or down to let water flow in and out as needed.

Drum Gates: Cylindrical, pivot to release water.

Drum gates are cylindrical gates that pivot to open and close, allowing for the release of water from a reservoir. Their rotating mechanism is advantageous for managing moderate water flows and offers easy operation. The design is beneficial especially in areas where space for traditional gates may be limited.

Think of a drum gate like a roll-top desk. When you pull down the drum, things (like water) can flow out easily. Just as you can control access to the desk’s contents, drum gates help regulate how much water is released from a dam.

Crest (Overflow) Gates: Movable panels regulating flow over spillway crest.

Crest gates, also known as overflow gates, are movable panels that adjust the flow of water over the top of a spillway. These gates help maintain the water level in a reservoir by allowing excess water to flow safely over the structure. They are crucial for managing high water events and ensuring dam safety.

Picture a bathtub with a drain and a movable cover. When the water gets too high, you can lift the cover to let some water overflow into the drain, therefore preventing the tub from spilling over. Crest gates work similarly to control how much water flows over the dam.

Stop Logs, Needle Gates: Temporary or adjustable wooden or metal barriers.

Stop logs and needle gates are types of barriers used to control water flow temporarily. Stop logs are typically wooden or metal planks that can be placed or removed to create a barrier across a spillway. Needle gates are similar but allow for more precise control of water flow using vertical rods that can be raised or lowered.

Imagine stacking blocks to stop water from flowing in a stream. You can easily remove or adjust the blocks as needed, similar to how stop logs and needle gates can be added or taken away to adjust water levels.

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