How to Measure Water Current of the Beni River?

1. Where is the Beni River?

The Beni River is one of the most striking and important watercourses in the South American continent. It is found in northern Bolivia, having its origin in the Andes Mountains.

It winds its way through diverse landscapes down from the lofty peaks of the Andes. It passes through dense rainforests, which are very thick because of the moisture it supplies. This river passes through a number of small indigenous communities along its path that depend on the Beni River for their livelihoods for quite some time now. These communities include people who have an exceptional likeliness for the river, mainly using it for fishing, transport, and water to perform daily activities.

This is the same river that forms part of the greater ecosystem in the area. The Beni houses a huge variety of life from numerous fish species, birds, and mammals. From the colourful birds perched on the branches overlooking the water to the caimans that lurk in its shallows, it's life all over.

Besides, the River Beni forms part of the geographical and cultural identity of Bolivia. It has been a witness to history and the tradition of the local inhabitants; stories and legends passed through the generations have been interlinked with its waters.

2. What does the Flow Rate of the Beni River Look Like?

The Beni River is of immense importance in the region through which it passes, being an integral part of Bolivia's water resources for various uses.

The discharge varies throughout the year, peaking during the rainy season that usually occurs from November until March. Because of heavy rainfall both in the Andes Mountains and in the catchment area around, the water precipitates down to the Beni River to reach a flow rate considerably higher. This high-water season is essential for restoring the volume of water in this river, washing out sediments, and keeping ecosystems healthy downstream.

For comparison, during the period of the dry season, from April to October, the flow rate of the Beni River diminishes. However, it still maintains a steady flow, which is important to keep up with the survival of the various organisms depending on it. The average flow rate of the Beni River ranges from several hundred cubic meters per second during the dry season to several thousand cubic meters per second at the height of the rainy season.

The volume of water flowing in the Beni River affects the transport and commerce across its banks. Boats and canoes are the normal mode of transport across the river, particularly when the volume of water becomes high during periods of high discharge.

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

Following are some of the methods for measuring water current of Beni River:

Velocity Meter Method

The traditional techniques consist of mechanical or electronic velocity meters. They are set up in discrete points along the river to measure the flow velocity at that particular point in the river. This technique requires cautious placement and has to involve many measurements in different positions and depths if one wants to make a reasonable estimate of the mean water current. This will, therefore, be quite time-consuming and involve high manpower when they may try to approximate for a large section of the river.

Acoustic Doppler Velocity Profiler (ADCP) Method

The ADCP method is more advanced and convenient in measuring water currents. It uses sound waves for detecting the movement of the water particles. It transmits acoustic signals and measures the velocity at several depths simultaneously by analyzing the Doppler shift of the reflected signals. This will provide a very detailed profile of the water current, which allows for more accurate evaluation of the flow conditions in the entire river. ADCP current profiler can be installed on boats, bridges, and even on buoys for continuous monitoring.

Buoy Method

It involves the buoy method where buoys are put in the river with sensors, which can measure the water movement around them. The buoys float on the surface and give some indication of the surface current. They may not be as accurate in fully capturing the complexity of the water current like the other means, particularly to understand the variation in velocity at different depths.

Among them, ADCP current meter is more advanced and efficient in measuring the water current of the Beni River.

4. How Do the ADCPs Using the Doppler Principle Work?

ADCPs are based upon the principle of Doppler. When an ADCP flow meter sends an acoustic signal into the water, the sound waves travel across the water and reflect back from the moving water particles. Due to the Doppler effect, the frequency of the reflected sound waves changes as the reflecting water particles are in motion.

Thus, if the water particles are approaching the ADCP meter, there will be a reflected wave frequency that is higher than the emitting frequency. It will be lower if the water particles move in the opposite direction of the ADCP. Precisely this change in frequency is measured by the ADCP in order to calculate the velocity of water at different depths.

Of these, the ADCP profiler ensembles at each of a number of different depth levels to achieve a full profile of the water current. This therefore allows for a very detailed understanding of how the water is flowing, not only at the surface but throughout the vertical section of the river.

5. What's Needed for High-Quality Measurement of the Beni River Currents?

To take a high-quality measurement, several factors become vital concerning the equipment of the currents of the Beni River.

First, it needs high material reliability. It needs to be able to withstand the harsh conditions that come along with the river environment: exposure to water, sediment, and temperatures.

These are small size, light weight, and low power consumption. Such a device will be more comfortable to handle and deploy both on a boat and attached to a buoy. Low power consumption means equipment will be capable of operating in a prolonged manner without needing frequent battery replacements or having access to a continuous power source.

Cost is another important factor. Lower cost allows the measurement equipment to be installed at more points, to comprehensively monitor the river.

In regard to casing, titanium alloy is an excellent choice of material for ADCP. The advantages of the titanium alloy are:. It has excellent resistance against corrosion, one of the most critical properties, since it would constantly come into contact with water and may contain some corrosive elements inside, taking into consideration bodies of water such as the Beni River. The material is also quite strong and able to handle most physical impacts and changes in pressure that may occur at its deployment and operation. Besides, titanium alloy has comparatively low density, contributing to the overall objective of keeping the equipment lightweight.

6. How to Choose Right Equipment for Current Measurement?

Selection of right equipment for measurement of current of the Beni River would depend on many factors.

Based on Use Purpose

If the horizontal cross-section of the river current is to be measured, an HADCP will be fitting for the purpose. In fact, the HADCPs are designed to provide accurate measurement in the horizontal plane of water flow, which helps in ascertaining the overall movement of water across any particular section of the river.

On the other hand, if the interest is in measuring the vertical cross-section of a river current, a vertical ADCP is what one should use. As a matter of fact, vertical ADCPs can measure with high accuracy a number of velocities of water at different depths so as to provide a well-detailed profile of how the water is flowing vertically within the river.

Based on Frequency

Frequency selection will also depend on the depth of water in the Beni River. This is due to the fact that it is always enough for the majority of the situations where the water has a depth of as many as 70 meters. The frequency of 600 kHz offers a very good resolution and accuracy for the measurement of the water current in relatively more shallow waters.

A 300 kHz ADCP would be appropriate for deeper waters, such as those above 70 meters and up to approximately 110 meters. Since the frequency is lower, at 300 kHz, it can penetrate further and still measure the water current reliably.

Some of the brands that are more well-known in the ADCP market include Teledyne RDI, Nortek, and Sontek. However, for those who only want to acquire it at a cheap price but with quite good quality, then China Sonar PandaADCP is one of those options. It is made from all-titanium alloy material and hence is durable and of high quality. Its super cost-performance ratio makes it one of the top choices to measure the water current of the Beni River. More information about this product can be found on its official website at: https://china-sonar.com/.

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