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

Leave a Comment

Your email address will not be published.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

More Articles

Design Ideas | A Creek-Style Waterscape with Koi

https://www.reddit.com/r/ponds/comments/pppd8e/my_small_creek_style_planter_pond_not_as_big_most/ This is a unique design from a professional contractor that emphasizes a ...

Blue Thumb Introduces the Heiho Fountain

The Heiho basalt fountain provides a simple way to add interest to your ...

Creating Water Gardens and Ponds in Kansas City

This one-of-a-kind very unique property feels like a high-end resort on an exotic ...

Big and Bold Website Redesign from Pond Trade

This kid is pointing to his favorite backyard pond, but also loves our ...

Contractor's Corner

Sponsored by Pondliner

Scroll to Top