How much water is required for a waterfall?
You must consider the size of your pond, width of the spillway, and desired water height (The effect of waterfall you want between trickle, sheet, and cascade). For a good flow, 200 GPH is needed for every 1 inch of waterfall spillway. So if you have a 16 inch spillway or waterfall weir you need a minimum of 3200 GPH.