How to Measure the Water Current of the Nen (Nonni) River

1. Where is the Nen (Nonni) River?

The Nen River, also called the Nonni River, is a major river in Northeast China. It is situated in Heilongjiang Province.

The river runs through an expansive plain area that is truly rich in fertile soil. It was an important part of the local water system and had great influence on the agricultural and transport sectors of the region. The farms in the surroundings rely on the river water for irrigation of crops such as soybeans, corn, and rice grown therein. Historically, it also served as a transportation route, allowing transportation of goods and people. The riverbanks are homes to different wildlife, such as wild ducks, herons, and fish. In addition, the floodplains and wetlands derived from the river contribute to the ecological balance of the area and provide breeding and feeding areas for many species.

2. What is the flow rate in the Nen (Nonni) River like?

The flow rate of the Nen River varies according to season and climate. During spring, with the melting of snow in the surroundings and increased rainfall, it increases abruptly. The river swells and can carry a higher amount of water during this period.

During summer and autumn, the flow rate decreases. It still retains, however, a base flow that is sufficient to sustain the different aquatic life and allow the continuity of the livelihood of the people in its surroundings, such as farming and fishing. During winter, its flow rate is further diminished, and during periods of extreme cold, certain portions of the river freeze. The average flow rate varies from a few cubic meters per second during the low-flow winter period to hundreds of cubic meters per second at the height of the spring runoff.

3. How to measure water current of the Nen (Nonni) River?

Velocity Meter Method

Traditional method involving the use of a mechanical or electronic velocity meter. These instruments are installed at distinct positions in the river and directly measure the velocity of water at that position. However, for a complete understanding of the overall current of water, several measurements have to be taken at different depths and parts of the river. Since the Nen or Nonni River is long and varies in many ways, this approach could be quite labor-intensive and take a lot of time.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter provides a more advanced and convenient way to measure water currents. It uses sound waves to detect 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 yields a very high-resolution profile of the current and thus allows one to better determine the flow conditions throughout the river with greater detail. ADCPs can be mounted on boats, for sites where the river is navigable, bridges (if available), or on buoys for continuous monitoring.

Buoy Method

The buoy method involves placing sensors that will measure the movement of water around them by putting buoys in the river. These buoys float on the surface and give an indication about the surface current. They do not capture the full complexity of water current with much precision, as would be seen by the other two methods, particularly the variation in velocity with depth.

Of these, the ADCP current profiler is more advanced and one of the finer ways of measuring the water current of the Nen (Nonni) River.

4. How do Doppler principle-based ADCPs work?

ADCPs work on the principle of Doppler. When an ADCP flow meter sends out an acoustic signal into the water, the sound waves travel through the water, which interacts with the moving particles of water. As the water particles are in motion, the frequency of the reflected sound waves gets changed by the Doppler effect.

If the water particles are coming towards the ADCP meter, then the reflected wave frequency will be higher than the frequency emitted. Whereas, if the water particles are going in the opposite direction from the ADCP, the frequency of the reflected wave will be lower. By accurately measuring this shift in frequency, the ADCP can find out how much velocity the water particles have at any depth.

These are then combined by the ADCP profiler to obtain a complete velocity profile at discrete depths. In this way, a proper idea of the flow of water right from the surface to the vertical section of the river can be obtained.

5. What's needed for high - quality measurement of the Nen (Nonni) river currents?

Therefore, some characteristics should be considered in the equipment to measure the Nen (Nonni) River currents accurately.

The equipment has to be highly material reliable. Due to the severe environment of the river systems, including direct contact with water, sediments, and temperature fluctuations, the equipment should be strong enough to bear them all in the dynamic nature of the Nen River and the debris often transported in this area during the high-flow periods.

Small size, light weight, and low power consumption are also desirable. A compact and lightweight device is easier to handle and deploy, whether it is on a boat or attached to a buoy. Low power consumption ensures the equipment can operate for long periods without the need to frequently replace batteries or access a continuous power source.

Cost - effectiveness is an important factor. A lower - cost option enables more widespread use of the measurement equipment, allowing for more comprehensive monitoring of the river.

When it comes to the casing of the ADCP meter, titanium alloy is an excellent choice. The resistance of the titanium alloy to corrosion is very high, which is especially important for treatment involving water bodies, like in the Nen (Nonni) River, where equipment would be in contact with water and other substances that might be corrosive. It is also strong and durable enough to withstand physical impacts, or the changes in pressure that might occur during deployment and operation. Also, titanium alloy has relatively low density, which allows the equipment to be lightweight.

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

In determining the appropriate type of equipment in measuring the current of the Nen (Nonni) River, some factors have to be considered.

Purpose of Use

A horizontal ADCP flow meter would be appropriate for an aim to measure the horizontal cross-section of the river current. HADCPs are designed to measure the water flow across the horizontal plane with accuracy, which will help in understanding the overall movement of water across a particular section of the river.

In case it has to do with the measurement of the vertical cross-section of the river current, then a vertical ADCP current profiler should be chosen. The velocity of the water at each depth is obtained with great accuracy by vertical ADCPs, which give a detailed profile of how water flows vertically in the river.

Based on Frequency

The frequency depends on the depth of water to be analyzed in the Nen (Nonni) River. For a water depth of about 70 meters, a 600 kHz ADCP is often adequate. The 600 kHz frequency provides good resolution and good accuracy for the measurement of the water current in relatively shallower waters.

For deeper waters, like over 70 meters up to approximately 110 meters, the 300 kHz ADCP would be more appropriate. The lower frequency of 300 kHz can penetrate deeper into the water and still provide reliable measurements of the water current.

There are renowned ADCP current meter brands such as 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 Nen (Nonni) 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.