In the construction of a pond, what is the function of a weir?

• A. Direct the flow of water from the lower to the upper pool
• B. Direct the flow of water
• C. Make the water fall away from the face of the wall
• D. Control flow of water from upper to lower pools

Answer: (D)

A weir acts as a barrier across a channel to regulate how much water moves from one pool to the next. In a pond, its job is to control the flow from the upper pool to the lower pool by letting water spill over a designed crest at a steady rate, which helps maintain target water levels and a manageable discharge. Because water naturally flows downhill, the weir’s function is not to push water from the lower to the upper pool, nor is it just a generic flow-directing device. It specifically governs the transfer from the upper to the lower pool, providing a controlled, predictable overflow.