## Measuring streamflow using the float method

Author(s): Nicolas Zegre

Brought to you by

River Field Studies Network

Summary:
Streamflow, the amount of water flowing in a creek, stream, or river at a certain point in time, is critical to people and the environment. Knowing the amount of flowing water is important for numerous water resources, ecological, and engineering…
Streamflow, the amount of water flowing in a creek, stream, or river at a certain point in time, is critical to people and the environment. Knowing the amount of flowing water is important for numerous water resources, ecological, and engineering applications including flood forecasting, ecosystem health, environmental flows assessment, infrastructure design, and water supply management used for drinking water, electricity production, manufacturing, and irrigation. In this lesson, students will learn how to measure and calculate streamflow in the field using the velocity-area method.

Version 1.0 - published on 17 Dec 2023 doi:10.25334/2DXT-EF12 - cite this

Contents:

#### Description

In this lesson, students will learn how to measure and calculate streamflow in the field using the velocity-area method and the float method. In the velocity-area method, streamflow is determined by multiplying stream velocity, the speed of water flowing in a stream channel, by the cross-sectional area of the stream channel that the water is flowing. Velocity is measured using the float method, a simple, low tech approach where the time it takes a “float” (e.g., small orange) to travel the distance from an upstream cross-section to a downstream cross-section. Additionally, students will survey stream channel cross-sections and calculate cross-sectional area using a reel tape to measure horizontal distances across the channel and a yard stick, ruler, or stadia rod to measure stream water depth.

Learning outcomes – By the end of this activity, you will be able to

• Discern basic hydrologic and geomorphic stream characteristics important to streamflow (channel depth, channel width, and calculation of cross-sectional area).
• Measure stream channel cross-sectional area using survey
• Measure streamflow velocity using the float method
• Calculate streamflow using the velocity-area equation

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