VIDEO: How To Measure Stream Flow

Today we’ve got a special video for you about how to measure stream flow. This tutorial is one of the ways we try to share with you best practices for determining water quality and stream health with help from EPA.

While our how to measure stream flow video above details all of this information, let’s give you the basics. Stream flow (also known as discharge) is the volume of water that moves over a designated point over a fixed period of time. It is often expressed as cubic feet per second (ft3/sec), as per EPA’s guidance. The measurement is important because it helps to determine the health of the watershed. Flow also gives you important information regarding the types of organisms that can live in the stream. For example, some organisms need high-speed, fast-flowing areas while others need quiet pools.

The video above should give you the basics of how to measure stream flow by floating an orange. While it sounds crazy, this method has proven time and time again to be effective. And most importantly, you can usually conduct the test with items you have in your office and/or garage. The clip above details the full process — including the math calculation aspect.

Below we’ve got a list of the items you’ll need as well as a link to EPA’s data form for calculating flow.


  • Ball of heavy-duty string, four stakes, and a hammer to drive the stakes into the ground. The string will be stretched across the width of the stream perpendicular to shore at two locations. The stakes are to anchor the string on each bank to form a transect line.
  • Tape measure (at least 20 feet)
  • Waterproof yardstick or other implement to measure water depth
  • Twist ties (to mark off intervals on the string of the transect line)
  • An orange and a fishing net (to scoop the orange out of the stream)
  • Stopwatch (or watch with a second hand)
  • Calculator (optional)

You can download EPA’s data calculation form by right-clicking the link to the left and choosing “save file as.”

Hopefully this video helps you get started in measuring stream flow.