Flow measurement in flowing waters (e.g. fish passes)

Flow velocity measurement in flowing waters such as streams and rivers



Process data

Measuring task:
Measuring flow velocity to calculate flow rate in rivers

Measuring point:
In rivers or waters

Measuring range:
Typically up to 4 m/s

Process pressure:

Process environment
Hydrostatic pressure
under water


Your advantage

Safe, easy and quick
Safe, quick and easy measurement under all weather conditions

Data can be saved in the handheld unit and later evaluated

Portable flow measurement in rivers with a handheld unit


In many flowing waters, flow measurement and water flows have to be measured and monitored regularly. This is necessary to ensure that the required, sufficient water amount remains for example after extraction through power plants or other users of flowing waters.   

Fish passes are fish lifts and need a sufficient amount of water. The goal is to enable the different kinds of fish to pass the fish lifts/ladders/passes etc. Pond farmers use the same sensors to monitor in- and outflow in fish ponds. In sewage plants flow velocity and flow rate are measured with the technique.  During floods flow velocity is measured in rivers to calculate consequences for the areas located downstream.

Höntzsch’s system solution allows portable measurement at different spots. Data is saved and can later be transferred to a data processor for a detailed data analysis.

Recommended products

Vane wheel ZS25 … ZG1

Product Product data sheet

Handheld unit Flowtherm NT.2

ProductProduct data sheet

What’s the flow velocity in waters?

In many flowing waters velocities and flows need to be monitored. In the German state Baden-Württemberg water to water the garden can be taken from flowing waters with watering cans or small pumps. The responsible district office can forbid it in case of too much water extraction to protect the ecosystem and avoid a trough. This requires legal certainty which can be obtained by measuring height and speed of the water. Otherwise legal action against this can be taken. Due to the large number of recurring measurements required (depending on the number of flowing waters), the measuring equipment must be reliable and robust. In smaller rivers levels can fluctuate 1 – 2 cm a week. The Höntzsch vane sheel sensor „ZS25“ is perfectly suited for this measurement since it can also measure low water levels.  

Do fish lifts fulfill their purpose?

Different varieties of fish lifts such as fish passes, fish ladders etc. are really important for species conservation in the eco system „flowing waters“. Fish lifts must be measured to ensure that all species occuring in that section of the river can pass the fish pass. In fish passes flow velocity is crucial since every fish has a different height that can rise to a certain velocity.

That’s why fish passes are displayed a certain way and measured when implementing. Flow monitoring is not only important for upstream fish migration, fish ladders or fish passes it’s also relevant for the increasingly used bed slides. Besides hydro-engineering tasks like reducing flow energy and therefore avoiding erosion damages at the bank and bed slides also have another important role in the eco system „flowing waters“: a bed slide ensures that fish and invertebrates can pass through the water like upstream fish migration and fish passes. All fish bypasses are to guarantee a passable fish path.

A requirement is enough flowing water covering the fish passes. In parallel to the flow velocity a temperature sensor can also be conncted to the same measuring device on the fish pass. That combination offers a better picture of the conditions for the fish at the fish passes.


What flow velocity is best for the fish?

Measuring flow velocity in swimming tunnels for fish is where the fish’s behavior is scientifically investigated at different, precisely measured flow velocities. It applies to fish in fresh and salt water and the used sensors are suited for both kinds of water.


Counter current system wanted?

Even humans train in counter current pools. Such systems make long distance swimming in small pools possible. The swimmer swims in one spot. Depending on liking and condition or training goal the speed can be regulated provided that it is precisely measured. For the analysis of flow in pools, checking the flow of springs and monitoring wells Höntzsch vane wheel sensors are perfectly suited.  


Easy cleaning

Cleaning the sensor happens after the measurement with clean water. Alcohol, dishwashing detergent and other cleaning supplies can also be used.