Sizing Your Stream or Waterfall Reservoir
A good rule of thumb for waterfall reservoirs is to make the reservoir 3 times the volume of the total water in the stream or waterfall.
EXAMPLE: Your stream is 3' wide and 20' long and has an average depth of 3". Use the water volume formula (width x length x depth x 7.5) to get the total water volume of the stream and waterfall.
3' wide x 20' long x .25' depth x 7.5 = 112.5 gallons. 112.5 gallons x 3 = 337.5
Your stream or waterfall basin will need to hold 337.5 gallons of water.