A weir is like a small dam built across a river or stream. Its main job is to manage and measure the flow of water.

Here’s how it helps with water management:

Measuring Water Flow: It helps you see how much water is flowing by making the water rise over the top.

Controlling Flow: It keeps the water levels steady, which can help prevent flooding or ensure there's enough water where it’s needed.

Diverting Water: You can use it to direct water to irrigation systems or reservoirs.

Preventing Erosion: By controlling how fast the water flows, it helps protect riverbanks from washing away.

So, think of a weir as a handy tool for managing and using water more effectively!