Aerial view of a flowing river

Flow and Discharge

Visualizing Streamflow Data for Actionable Insights

Dominated by the force of gravity, flowing water replenishes ecosystems and communities as it moves through a watershed, or an area of land that drains water into a specific outlet. Snowpack, drought, precipitation, and human activity all alter how much water is output or discharged by a stream. In a changing climate, accurately monitoring streamflow and correctly calculating discharge is imperative for water resource professionals to:

For decades, OTT HydroMet’s leading brands of SUTRON and OTT products have evolved to support customers in the development of their watershed monitoring networks by innovating sensor technology, solving workflow challenges, and improving confidence in their data quality. Today, we offer a vast portfolio of sensors and intuitive software to ultimately provide you with continuous insight into your streams’ behavior.

Key Features and Benefits

Woman using an OTT MF Pro flow meter to measure depth and velocity in a stream

Directly Measuring Stream Velocity

OTT HydroMet has been a leader in flow meter technology for over 100 years, from the first mechanical velocity meters to the advanced acoustic Doppler and radar technology used today. Stream velocity can be measured continuously with a mounted, non-contact OTT Surface Velocity Radar (SVR) or in-stream using a portable flow meter, like the OTT MF Pro. When profiling a stream, a flow meter is used to collect depth and velocity data in subsections along a cross-section of a stream, this provides site-specific velocity and area measurements to plug into a discharge equation.

Leveraging Stage for Continuous Stream Gaging

The dynamic nature of flowing water limits our ability to continuously measure discharge via stream velocity. However, there is another parameter that has long been the foundation of streamflow monitoring: water level, also known as stage.

Depending on existing infrastructure, stage measurements are taken using different OTT HydroMet sensors:

Contactless OTT SVR 100 flow sensor and RLS level sensor measuring stream velocity and water level

A stilling well fills with water from the stream through an intake while maintaining the same water level as the stream. Inside the well, a pressure level sensor or float are used to continuously detect water level changes. If a bridge is present, a non-contact Radar Level Sensor (RLS) and Surface Velocity Radar (SVR) can be used in combination to continuously measure water level and velocity.

Software displaying a rating curve development tool

Developing a Stage-Discharge Relation

Streamflow, or discharge cannot be measured continuously with a sensor, instead hydrologists combine continuous stage, or water level data with a series of corresponding spot discharge measurement to determine a stage-discharge relationship or rating curve.

Water Data Management and Visualization

Software solutions, like Aquarius, visualize this complex relationship of water level, velocity, and discharge data into a user-friendly interface that allow you to manage the stage / Q relationship overtime.

A site-specific rating curve provides insight into how a stream has historically behaved and allows water resource professionals to extrapolate future discharge values. For example, accurate stream monitoring assists in forecasting the likelihood of a flood event.

Once a stream is profiled and sensors are installed, they can be seamlessly integrated into a datalogger recording at specified intervals (i.e 15 minutes) and voila! You have yourself a remote stream gaging station. The unique ability of specific dataloggers to transmit water data back to your office transforms the way streamflow and discharge are remotely monitored.

Supplement Quantitative Data with a Camera Addition

Enhance your stream monitoring network with visual confirmation. This growing trend provides your eyes in the field for qualitative context to sensor readings and remote access to current conditions.

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camera addition to a stream monitoring station

Surface Water Quantity Insights

Learn about the versatile technology options for the measurement of water level, velocity, and discharge in the Application Matrix for Surface Water Quantity.

View Guide

Cover of Guide displaying open channel with surface water

Flow and Discharge Related Resources

OTT MF Pro flow meter

Water Velocity Flow Meter

View a visual walkthrough on the OTT MF pro, a user-friendly, low maintenance electromagnetic flow meter for cost-efficient in-stream discharge measurement.

Watch Video

OTT SVR contactless velocity radar sensor

OTT SVR 100 Benefits

Learn more about the OTT Surface Velocity Radar (SVR) in this on-demand webinar.

Watch Webinar

Tablet and computer displaying water management software

Introducing AQUARIUS Software

A highly customizable water resource monitoring software system that is revolutionizing the way water data is managed, analyzed, stored, and delivered.

Watch Video

Surface Water Application Page

A Thirst for Knowledge: Harnessing the Power of Data to Solve Our Water Challenges

An exploration of four key water data management milestones to ensure the sustainability of our most valuable resource.

Read eBook

In the Field

Dam and reservoir with mountains in the background

FERC Regulatory Compliance & Water Accounting

See how a Northern California power agency was able to streamline their complex regulatory reporting, plus:

  • Manage & compute all water data in accordance with USGS standards
  • Build more accurate rating curves in less time

All through AQUARIUS Time-Series software.

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Related Products

Your selection

  • Water Discharge - Flow
  • Fixed Flow Meters
  • Portable Flow Meter




Product Type


OTT SVR 100 Surface Velocity Radar
Price: Contact Us
OTT MF pro Meter, Portable with Case
Price: Contact Us

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