What does the size of the weir opening primarily control?

• A. The depth of the pool
• B. The amount of water that passes to the falls
• C. The color of the water
• D. The pressure in the system

Answer: (B)

The size of the weir opening controls how much water can pass through per unit time. A larger opening lets more water flow toward the falls, increasing the discharge and the volume of water visible in the waterfall. The color of the water isn’t determined by how much water is flowing—it’s influenced by clarity, lighting, minerals, and any algae. System pressure, meanwhile, comes from the pump and the piping layout, not directly from the weir opening. Pool depth is set mainly by the overall water balance and storage in the upstream area, not by the opening size itself. So the primary effect is the amount of water that reaches the falls.