How to Measure Water Current of Olyokma River?

1. Where is Olyokma River?

The Olyokma River is a major river in Russia. It is situated within the Trans - Baikal region and forms a key part of the Lena River basin. The river flows across a large area comprising taiga forests, mountainous areas, and extensive floodplains.

This river passes through sparsely populated territories with small indigenous settlements and remote villages dotting its banks. The local communities have one thing in common: deep connections with the Olyokma River. Quite often, the livelihood in these places depends on fishing, as the river is heavily populated with fish species like lenok, grayling, and taimen. It provides food from hunting and gathering within the surrounding forests, as well as transportation by the river during its ice-free period.

The Olyokma River is culturally very important: much traditional knowledge and many tales are associated with the river among indigenous peoples. It forms a part of their oral history, spiritual beliefs, and continuation of their unique cultures through time, all of which its waters have seen.

2. What is the flow rate in the Olyokma river?

The flow rate of the Olyokma River is subject to seasonal fluctuations: in spring, snow melting in the surrounding mountains and forests results in a serious rise in the river. The water level rises, and the current becomes powerful, carrying with it a great deal of sediment and debris. This period is important for the river's ecological cycle because it redistributes nutrients and shapes the riverbed and floodplains.

In summer, the rate of flow stabilizes somewhat. The river still flows fairly strongly and supports a considerable amount of aquatic life as well as providing water for surrounding ecosystems. The river freezes in winter, and any flow beneath the ice is much reduced. The average flow rate is influenced by factors such as the amount of precipitation in its catchment area, the topography of the basin, and the presence of tributaries that contribute to the overall water volume.

3. How to measure water current of Olyokma River?

There are several methods to measure the water current of the Olyokma River:

Velocity Meter Method: This is the usage of mechanical or electronic velocity meters. These meters are placed at various positions in the water, at which the speed of water passing by is measured. The problem with this method is that there is a need for repeated placement at different locations and depth to understand the current fully. It can be very time-consuming and may not result in a continuous profile throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method: This is a better and advanced method of measuring water current. It measures the velocity at different depth points simultaneously with the use of sound waves. ADCP can give an accurate and detailed profile of the current from surface to riverbed through the reflection of emitted acoustic signals due to the Doppler shift effect. This allows for a rather more accurate and comprehensive measurement of the water current across varied sections of the river.

Buoy Method: In this technique, buoys are installed in the river and their movements are monitored over a period of time. The lateral displacement of the buoys by water current provides an approximation of the speed and direction of flow. This, however, has its shortcomings. It may not be effective in giving the exact velocity at different depths and is susceptible to interference from other agents like wind and waves, which may affect the movement of the buoys.

Of all these, the ADCP method is the most advanced and convenient means of measuring the water current of the Olyokma River.

4. How do Doppler Principle Using ADCPs Work?

ADCPs work on the principle of the Doppler effect. When an acoustic signal is transmitted from the ADCP transducer into the water, the sound waves encounter and interact with the moving particles of water. Due to the flow of water, the frequency of the reflected sound waves back to the transducer changes-a phenomenon known as the Doppler shift.

If the water is moving towards the transducer, the frequency of the reflected waves will be higher than the emitted frequency. If the water is moving away from the transducer, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP calculates the velocity of the water in different directions and at various levels within the water column. This enables it to create a detailed profile of the water current, providing valuable information about the speed and direction of the flow from the surface to the riverbed.

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

The equipment should possess certain qualities for high - quality measurement in the Olyokma River currents. The materials of its construction have to be reliable for making accurate and consistent measurements of the speed of water streams. Small size is desirable since it will facilitate its deployment in the river and retrieval in places of difficult access, while small weight will essentially simplify installation works and minimize efforts required for handling it.

Low power consumption is essential to ensure that the equipment can operate for extended periods without the need for frequent battery replacements or a complex power supply setup. Cost - effectiveness is another important factor as it enables more widespread use and larger - scale measurement campaigns.

When it comes to the casing of the ADCP, titanium alloy is an excellent choice. Titanium alloy has many advantages. It is highly resistant to corrosion, which is essential since the equipment is always in contact with water that could contain a number of minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, enabling a durable yet lightweight casing. In addition, it is resistant to the mechanical stresses occurring during deployment and operation in flowing water of the Olyokma River.

6. How to Select proper equipment for current measurement?

For choosing proper equipment for the measurement of Olyokma River's currents, there are basically two primary factors:

Depending on the usage purpose, for a horizontal cross - section measurement, HADCP is suitable. It is designed for the accurate measurement of flow velocities across a horizontal plane in the river, which is useful to understand the lateral distribution of the current. In the case of vertical cross-section measurement, Vertical ADCP is more appropriate since it focuses on profiling from the surface to the bottom along a vertical line in the water column.

Second, different frequencies of ADCPs are suitable for different water depths. For instance, the 600 kHz frequency of an ADCP is suitable for a water depth within 70 m. It can give quite good current measurements in the relatively shallower parts of the Olyokma River. For deeper waters of up to 110 m, it would be better to use an ADCP with a frequency of 300 kHz, which could work well where the river is much deeper.

There are well - known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with good quality, the China Sonar PandaADCP is highly recommended. It is made of all - titanium alloy material and offers an incredible price - performance ratio. You can find out more about it on its website: https://china-sonar.com/.

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