How to Measure Water Current of the Oka River?

1. Where is the Oka River?

The Oka River is among one of the largest water bodies of the European part of Russia, whose source is in the central part of the Valdai Hills. It then follows a tortuous course and breaks through different kinds of landscapes.

The river passes through so many regions and cities that have an intimate relationship with it, while meandering south. Then, it cuts across the Moscow Region. In fact, Moscow city is not far away from its basin. The river has played a part in the historical and cultural upbringing of the areas that it passes. The Oka River is a very valuable water body since many towns and villages along its banks have benefited a lot from its water supply for use in various functions, such as fishing and as a transport channel in the old days.

The Oka River is also an indispensable component of the local ecosystems. Its waters host a varied population of fish, including many species like pike, perch, and roach. Lush vegetation along the riverbanks provides a habitat for birds, mammals, and insects. Wetlands and floodplains next to the river offer important breeding and feeding areas for many species of wildlife.

Besides, it presents a natural border in some territories and has determined the structure and development of settlement through ages.

2. What Does the Flow Rate of the Oka River Look Like?

The flow rate of the Oka River shows pronounced seasonal variations; it rises considerably during the spring-the period of snow melting in its catchment area in the Valdai Hills and elsewhere upstream. A sufficiently large volume of water poured downstream after the snow and ice start to get melted, raising the relatively high flow rate.

The above high-water season is essential to the recharge in volume of water within the river, ensuring continued ecological health downstream, and to move sediments. It will also affect flood control and management of water resources in the areas that the river flows through.

During the summer into fall, the flow rate decreases as the snowmelt is dissipated and with changes in precipitation. The base flow in the river, however, is substantial for sustaining all aquatic life, sport fishing, and some kinds of industrial use that need a minimum water level for domestic purposes.

During winter, portions of the river freeze, while the flow rate in such parts of the section drops to a minimum. With regard to averaged values, the flow rate can range from a few hundred cubic meters per second during low-water periods to several thousands of cubic meters per second during the peak of snow melting in spring.

3. How to Measure Water Current of the Oka River?

Velocity Meter Method

The conventional technique: this technique employs mechanical or electrical velocity meters. These are commonly mounted at multiple locations across a stream and directly measure the water current velocities at the respective locations. It requires cautious installation and generally requires multiple readings at various profundities and positions to obtain an excellent view of the average water current. In the case of Oka River, this is extremely cumbersome and requires more time due to the fact that the river has longer length and varies in different stretches.

Acoustic Doppler Velocity Profiler ADCP Method: The ADCP represents a more modern and much handier method of measurement in the field of water currents. It depends on the use of sound waves to determine the velocity of the water particles. It makes a measurement of the velocity of the water at several depths simultaneously by emitting acoustic signals and analyzing the Doppler shift of the reflected signals. This provides a very accurate profile of the water current, which allows for a much more correct evaluation of the flow conditions in the entire river. ADCPs may be installed on boats, on bridges, or even launched on buoys for continuous monitoring.

Buoy Method

The buoy method simply involves setting buoys in the river with installed sensors that have the capacity to measure the movement of the water around them. The buoys will float on the surface and can give some indication of the surface current. However, they may not capture the full complexity of the water current as precisely as the other methods provide, particularly with regard to the variations of the velocity at different depths.

Among the existing methods, the most sophisticated technique to measure the water current of Oka River has proved to be an ADCP current profiler. 

4. How Do Doppler Principle ADCPs Work?

Principle of Doppler is what the Acoustic Doppler Current Profiler (ADCP) work on. When an ADCP sends out an acoustic signal into the water, the sound waves transmitted travel through the water and have some scattering with the moving water particles. Due to the motion of the water particles, the frequency of the reflected sound waves will fall under the Doppler effect.

If the water particles are moving towards the ADCP current meter, then the reflected wave frequency is higher than the emitted frequency. While if the particles of the water are moving away from the ADCP profiler, the reflected wave frequency would be lower. Precise measurement of this shift in frequency lets it determine the velocity of the water particles at all those different depths.

The ADCP flow meter sums up these discrete measurements taken at all depths to obtain a complete profile of the water current. This has been enabling one to gain an appropriate understanding of the flow of the water-not only at the surface but throughout the depth of the vertical section of the river.

5. What's Needed for High Quality Measurement of Oka River Currents?

Several issues related to the equipment are highly relevant for obtaining high-quality measurements of Oka River currents.

First, it needs to possess a high level of material reliability. It should be resistant to all that complicates a river environment: its interaction with water, sediment, and temperature variations. Given that different seasons take turns in the Oka River region, and considering the other probable influences during those seasons like floods, only strong equipment would serve.

Besides this, the device preferably should be of a small size, light, and with low power consumption. The compact and lightweight device is easy to manipulate and launch, whether from a boat or attached to a buoy. Low power consumption means equipment will be able to operate for long periods without needing frequent replacement of batteries or access to a continuous power source.

Another important factor is cost. A lesser cost implies that the measurement equipment can be put up in many more numbers to cover the entire length and breadth of the river.

When it comes to casing in the ADCP meter, the best material that can be used is the titanium alloy. Titanium alloy has several advantages. It is highly resistant to corrosion, which is so vital in the case of water bodies like that of Oka River, where equipment is continuously exposed to water and thus corrosive agents. Hard and durable, it will easily resist physical impacts as well as pressure changes during the deployment and operation process. The density of the titanium alloy is also relatively low, toward the aim of making the equipment light.

6. How to Choose the Right Equipment for Current Measurement?

Selecting the right equipment for measurement of the current of the Oka River involves several issues that need to be considered.

Based on the Purpose of Use

If the intention is to measure the horizontal cross-section of the river current, then a horizontal ADCP has to be used. The design of HADCP allows for accurate measurements of water flow in the horizontal plane, thus helping in ascertaining the overall movement of water across any particular section of the river.

On the other hand, if the focus is on measuring the vertical cross-section of the river current, a vertical ADCP should be selected. Vertical ADCPs can very accurately measure the water velocity at many different depths and can give a very specific profile of how the water is actually flowing vertically within the river.

Based on Frequency

Frequency choice is also dependent on the water depth of the Oka River. For such a scenario, at water depths less than 70 m, a 600 kHz ADCP can be appropriate. The 600 kHz will serve well for good resolution and accuracy in measuring the water current for such relatively shallow waters.

Therefore, for waters deeper-say over 70 meters to approximately 110 meters-the more appropriate device would be a 300 kHz ADCP. A lower frequency of 300 kHz could travel further into the water while still being reliable to measure the water current.

There are several known brands in the ADCP market, including Teledyne RDI, Nortek, and Sontek. However, for those looking for an affordable option with great quality, one may want to check out the China Sonar PandaADCP. It is totally made of titanium alloy material, featuring strength and reliability. With its incredible price-to-performance ratio, it certainly provides an exemplary alternative in water current measurement for the Oka River. More about it can be found on its official website: https://china-sonar.com/.

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