How to Measure the Water Current of the Bermejo River

1. Where is the Bermejo River?

The Bermejo River is one of the great watercourses in South America. Its source is located in the highlands of the Andes in Bolivia; after that, it flows down through Argentina. This river goes through a different and striking landscape that contains mountainous areas at its source, giving place to extensive plains and valleys as it usually courses along the land.

It covers areas along its course that are historic and culturally rich. In Argentina, it flows near several towns and rural communities that have been long caught up in its rhythms. For all these long years, local people have depended on the Bermejo River for many aspects of their lives. It has served as a water source for irrigation, thus allowing crops such as maize, wheat, and different fruits that grow in the region's climate.

The river also provides essential services in the ecology of the areas it passes through. It shelters various types of fish species, such as catfish and many other varieties of native characins, within its waters. Its banks are nesting sites for numerous bird species, which include colorful songbirds and huge raptors. Besides that, amphibians, reptiles, and mammals are also commonly seen on the edges of the river, making it a dynamic and integral part of the local wildlife habitat.

2. What is the flow rate of the Bermejo River like?

The Bermejo River is important to the many regions within which it runs. The water is a fundamental part of agriculture in the area, as well as an important route for transportation, though this is considerably less common today than in the past, when all goods carried along its length depended upon boats.

The flow rate of the Bermejo River varies significantly over the year. During the wet season, which is typically influenced by the monsoon-like patterns in the region, heavy rainfall in its catchment area leads to a significant increase in the river's flow. The water volume surges, and the river can become quite powerful, carrying large amounts of sediment and debris downstream. The flow rate during this period can reach several thousand cubic meters per second in some sections.

When it is dry, the flow rate significantly lowers. The river's width contracts and the water level goes down, but it still sustains a base flow which is critical to the survival of the aquatic organisms thriving in it. This base flow also caters to the limited irrigation requirements of the farmers in times of drier months. In the dry season, this flow may vary from a few hundred cubic meters per second to a thousand cubic meters per second in different parts of the river.

3. Cómo medir la corriente de agua del Río Bermejo?

Velocity Meter Method

This traditional method uses mechanical or electronic velocity meters. These devices are installed in the specific position in the river from where the speed of water at that particular position can be directly measured. However, for understanding the overall water current of the Bermejo River, much multiple measures need to be taken at different depths and at different sections. With the length and variable conditions of the river, this may be fairly labor-intensive and time-consuming.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current meter method presents a more modern and convenient technique of measuring water currents. It relies on the use of sound waves in detecting the movement of water particles. It basically measures the velocity of water at several depths of water by generating acoustic signals and analyzing the Doppler shift of the reflected signals. This remarkable capability provides a very detailed profile of the water current, hence enabling a much more accurate assessment of flow conditions along the full length of the Bermejo River. ADCPs can be mounted on boats, which can navigate along the river to gather data, or they can be installed on bridges or even deployed on buoys for continuous monitoring.

Buoy Method

The buoy approach involves setting buoys in the river fitted with sensors meant to be able to sense the motion of the water around them. These buoys float at the surface and may provide some information on the surface current. However, they may be unable to accurately model the full complexity of the water current to a greater extent than the other methods, in regard to finding out how the variation in depth beneath the bed of the river affects velocity.

Among these techniques, the ADCP current profiler is an advanced and effective alternative to determine the water current of the Bermejo River.

4. How do ADCPs using the principle of the Doppler work?

ADCPs work on the basis of the Doppler principle. When an ADCP flow meter sends an acoustic signal into the water, the sound waves travel through the water and contact the moving water particles. Due to the movement of the water particles, there is a change in frequency when the sound waves are reflected back, according to the Doppler effect.

If water is moving towards the ADCP profiler, it would shift the frequency of the reflected wave higher than that emitted. If the water is moving away from the ADCP, the frequency of the reflected wave will be lower. By precisely measuring this change in frequency, the ADCP calculates the velocity of water particles at different depths.

These individual velocity measurements at different depths are then combined by the acoustic doppler velocity meter to give the complete profile of the water current. This, therefore, allows for a detailed understanding not only of the water flow on the surface but throughout the vertical section of the river.

5. What's needed to obtain high-quality measurement of the Bermejo river currents?

For high-quality measurement of the Bermejo River currents, the equipment must possess certain key characteristics.

First of all, high material reliability. That is to say, it should be able to resist the severe conditions that can arise in a river environment; in other words, it should be resistant to water, sediment, and temperature ranges, among others. The fluctuations in the Bermejo River current and debris carried in periods of high current require solid equipment capable of withstanding them without deteriorating or malfunctioning.

It is highly desirable that the device be compact in size, lightweight, and have low power consumption. A compact, light device is much easier to handle and deploy, be it on a boat, attached to a buoy, or installed in other places along the river. Low power consumption means the equipment will be operational for prolonged periods without needing replacements of its batteries or a constant feed from a power source, which is particularly important in remote or difficult-to-reach areas.

The another important point is the cost-effectiveness. The more economical one can be used widely in the usage of measurement equipment for wider application to monitor the river. Titanium alloy is an excellent choice for casing ADCP. For such an application like the Bermejo River, where the equipment is constantly in contact with water-possibly corrosive substances-corrosion resistance of the titanium alloy is highly adequate. On the other hand, its strength and toughness mean that physical impacts and pressure changes are tolerable during deployment and operation. The density of the titanium alloy is relatively low, another plus for keeping the equipment lightweight.

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

While selecting appropriate equipment for measuring the current of the Bermejo River, a number of factors shall have to be considered.

Based on the Purpose of Use

The horizontal ADCP is the one to use if one intends to measure the river current in terms of its horizontal cross-section. Horizontal ADCPs are designed for giving accurate measurements of water flow in the horizontal plane, which would be useful in understanding the overall movement of water across that section of the river.

If the focus is to measure the vertical cross-section of the river current, a vertical ADCP should be chosen. Vertical ADCPs can accurately measure the water's velocity at each different depth to provide a finely detailed profile in the vertical aspect of the water flow in the river.

Based on the Frequency

The choice of frequency takes into account the depth of the water in the Bermejo River. For water depths up to 70 meters, a 600 kHz ADCP would normally be appropriate. This 600 kHz frequency offers good resolution and accuracy in the measurement of the water current in relatively shallower waters.

A 300 kHz ADCP will be more appropriate in waters exceeding 70 meters up to about 110 meters. This is because the lower frequency of 300 kHz can go deeper into the water and still give trusted measurements of the water current.

There are famous ADCP brands, like Teledyne RDI, Nortek, and Sontek. However, for those who are looking for a cheaper option with very good quality, the China Sonar PandaADCP would be a good option. It is made of all-titanium alloy material for durability and reliability. The cost-performance ratio is very remarkable, providing a great alternative to measure the water current of the Bermejo River. More details can be seen on its official website: https://china-sonar.com/.

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