Tech Tip | How To Calculate Waterfall Flow

Published on December 28, 2020

>> This is a sidebar to Demi Fortuna’s main feature, “A Pump and Plumbing Pond Primer”

What if you wanted to know the flow of an existing waterfall, perhaps because you want to recreate the same effect? You can measure the thickness of the water flowing over a spillway or fall rock. Turn a ruler or tape sideways or perpendicular to the flow to get as accurate a reading as possible. (Remember, the water will be in motion.) For an irregular surface, measure every 4 — 6 inches and take the average depth of the water spilling over the top of the waterfall rock or spillway. Just like before, multiply by the width of the waterfall to get the total flow.

  • ¼” — 3/16” depth of water over spillway ≈ 50 gph/inch
  • ½” — 5/8” depth of water over spillway ≈ 100 gph/inch
  • 1” — 1¼” depth of water over spillway ≈ 200 gph/inch

For a more accurate reading on smaller falls, it’s sometimes possible to measure the flow directly using a piece of scrap liner and some gravel. Turn off the pump and cover the falls with the liner, anchoring the upstream edge with gravel. Fold the rest of the liner into a 5-gallon pail and turn on the pump. Measure the number of seconds it takes to fill the pail. (You will get wet.) The flow in gph will be equal to the number of seconds in an hour, times 5 gallons, divided by the time it takes to fill the bucket in seconds:

GPH = 3,600 sec/hour x X gal / Y sec

Kloubec Koi Farm

Leave a Comment

Your email address will not be published. Required fields are marked *

More Articles

EasyPro’s 2022 Catalogs Now Available!

EasyPro Pond Products offers two specialized catalogs. The Pond & Water Feature catalog ...

Outdoor Water Solutions Acquires Air-O-Lator

Outdoor Water Solutions, Inc. has acquired Air-O-Lator, a water and wastewater equipment manufacturing ...

A Beach-Side Water Feature Renovation

The condo association, as well as the residents, felt the water feature was ...

Attend and Register for the 2022 Water Garden Expo

Pondliner Wholesale’s Water Garden Expo returns to the Heart of Oklahoma Exposition Center ...

Contractor's Corner

Sponsored by Pondliner

Scroll to Top