How to Measure the Water Current of the Narew River

1. Where is the Narew River?

The Narew River is in northeastern Poland and northeastern Belarus. It constitutes a tributary of the Vistula River.

The river passes through a landscape that contains forests, meadows, and wetlands. The area on both sides of the Narew River is biologically diverse. It forms a habitat for many species of plants and animals. One can note, for example, different fish species, waterbirds such as herons and cranes, mammals like beavers and otters living in or around the river. It actively participates in the general water circulation and flood control within the region. The floodplains of the Narew River contribute much to the purification of water and replenishment of groundwaters.

2. What is the flow rate in the Narew River like?

The flow rate of the Narew River is subject to seasonal and climatic variations. In the spring, snowmelt from the surrounding areas and increased rainfall can lead to a significant increase in the river's flow. The river swells and can carry a larger volume of water during this period.

During the summer and fall, the flow rate decreases. It retains, however, a base flow supportive of fish life and fisheries, recreational uses like canoeing, and abstraction for various purposes. In winter, this flow rate can be reduced further, and in cold conditions, partial freezing can occur. The average flow rate varies from a few cubic meters per second in the low-flow winter period to several hundred cubic meters per second during the peak of the spring runoff.

3. How to measure the water current of the Narew River?

Velocity Meter Method

This classical approach involves the use of mechanical or electric velocity meters. These instruments are introduced into the river at selected points to measure the velocity of flow directly at those points. Nevertheless, for an overall understanding of the water current, several readings must be taken across various water depths and sections of the river. Due to the longer length and changing conditions within Narew River, this can be quite labor-intensive and time-consuming.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current meter offers a more sophisticated and handy operation of water current measurement. It relies on the use of sound waves in detecting the movement of water particles. By emitting acoustic signals and analyzing the Doppler shift of the reflected signals, it can measure the velocity of water at multiple depths simultaneously. This gives a very good profile of the water current and offers a more accurate determination of the flow conditions along the river. The ADCPs can be installed on boats- Provided the river is navigable, on bridges- if present, or deployed on buoys for continuous monitoring.

Buoy Method

The buoy approach consists of placing buoys in the river equipped with sensors that are able to measure the movements of the water around them. The buoys float on the surface and can provide some indication of the surface current. However, they cannot capture the full complexity of the water current as accurately as the other methods may do, especially when it comes to understanding the variation in velocity across different depths.

Among these techniques, ADCP current profiler is more advanced and efficient for the measurement of the water current in the Narew River.

4. How do ADCPs using the Doppler principle work?

ADCPs operate by the Doppler principle. If an ADCP flow meter sends out an acoustic signal in the water, then the sound waves begin to travel through water and start their interaction with the moving particles of the water. Since these water particles are in motion, due to the Doppler effect, the reflected sound waves will return with a different frequency.

If the water particles are moving towards the ADCP meter, then the reflected wave frequency would be higher than the emitted frequency. In contrast, the reflected wave frequency is lower if the water particles are moving away from the ADCP. Precise measurement of this change in frequency makes the ADCP able to calculate the velocity of the water particles at different depths.

Afterwards, the ADCP profiler combines these individual velocity measurements, taken at different depths, into a complete profile of the water current. This allows for a detailed understanding of how the water is flowing not only at the surface but also throughout the vertical section of the river.

5. What's needed for high - quality measurement of the Narew river currents?

To measure the currents of the Narew River at a high quality, some characteristics are required for the equipment.

The construction material of the equipment should be highly reliable. The equipment is supposed to resist extreme conditions such as exposure to water, sediment, and temperature fluctuations in the river environment. The flow of the Narew River is variable, and during periods of high flow, there is debris that requires resistance by the equipment.

Another important factor is that the size should be as small as possible, the weight lightweight, and the power consumption low. A device that is compact and lightweight is easier to handle and deploy, whether on a boat or attached to a buoy. Low power consumption ensures that equipment can operate for extended periods without needing frequent battery replacements or access to a continuous power source.

Cost-effectiveness is also an important consideration. A cheaper option could facilitate wider use of the measurement equipment, providing comprehensive coverage of the river.

For casing of the ADCP, the metal of choice should be a titanium alloy. The resistance of titanium alloy to corrosion is quite high, an important factor when dealing with water bodies like that of the Narew River, where the equipment is literally in contact with water and, possibly, corrosive substances day in and day out. Besides, the material is strong and durable, able to withstand physical impacts and the pressure changes that may happen upon deployment and operation. Besides that, titanium alloy has a relatively low density in contributing to the overall goal of keeping the equipment lightweight.

6. How to Choose the right equipment for current measurement?

When it comes to choosing the right equipment for measuring the current of the Narew River, a number of factors are to be considered.

Based on the Purpose of Use

If the intention is to measure the horizontal cross-section of the river current, the horizontal ADCP flow meter should be used. The horizontal ADCPs will be able to give proper and appropriate performance by showing the actual measurement of the water flow in a horizontal plane that will support the general movement of water across a specific area or section of the river.

If the intention is to measure the river current's vertical cross-section, then a vertical ADCP current profiler should be chosen. Vertical ADCPs are capable of accurately gauging the water's velocity at various depths to obtain an in-depth profile of the water flow vertically across the river.

Based on Frequency

This depends on the depth of water in the Narew River. Usually, a 600 kHz ADCP is a good option when the depth of the water is up to 70 meters. The 600 kHz frequency provides good resolution and accuracy for measuring the water current in relatively shallower waters.

For the deeper waters that go over 70 meters and up to approximately 110 meters, it would be better to use the 300 kHz ADCP. At a lower frequency of 300 kHz, deeper water can be effectively permeated and allow for appropriate measurement of the water current.

There are known ADCP current meter brands like Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective option with excellent quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, ensuring durability and reliability. With its remarkable cost - performance ratio, it provides a great alternative for measuring the water current of the Narew River. You can find more information about it on its official website: https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.