How to Measure the Water Current of the Juruena River

1. Where is the Juruena River?

The Juruena River is in Brazil. It is a big tributary of the Tapajós River, which in turn is a tributary of the Amazon River.

The Juruena River runs through a wide area of the Amazon rainforest. It's a richly biodiverse region with the river as an important form of transportation among the indigenous communities. Local people navigate their canoes to move downstream or upstream along the river to reach another part of the forest in order to hunt, fish, or gather. Most of the fish species such as catfish and piranhas could be found there. The riverbanks and the surrounding rainforest are a home to many unique wildlife species, including jaguars, monkeys, and a variety of birds and reptiles.

2. What is the flow rate in the Juruena River?

The flow rate of the Juruena River varies with seasons and climate. The Amazon region has a wet and a dry season. In the wet season, from December to May, heavy rainfall in the catchment area causes a huge rise in the river's flow. The river swells and can carry a large volume of water, sometimes even flooding the adjacent forest areas.

From June to November, the flow rate reduces during the dry season. The base flow is, however, still maintained at a level that is crucial for the survival of aquatic life and to support the activities of the local communities such as fishing and transportation. The average flow rate can be in the range of a few hundred cubic meters per second during the dry season to several thousand cubic meters per second during the peak of the wet season.

3. How to measure the water current of the Juruena River?

Velocity Meter Method

The classic system relies on mechanical or electrical velocity meters. Devices such as these are taken out into the river at preselected points and give the speed of the water there directly. But, because of this, numerous samples will have to be done from top to bottom in deep spots and across the stream so one can get a real measurement for the average water current. In that case, considering the long length and very difficult navigation by thick rainforest on every side of the Juruena River, this methodology is quite labor-consuming and may take more time to conduct.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter does almost the same but with better facility. The basic principles consist of sound waves, with its echoes being utilized for identifying moving particles. The unit will be able to acquire the velocity of water in various depths simultaneously by emitting the acoustic signals and analyzing the Doppler shift of reflected signals. This gives one a very good profile of the water current, as well as a more proper perception about the flow conditions on the entire river. ADCPs are also mountable in boats where the conditions allow navigating the stream, or even installed on buoys for continuous monitoring.

Buoy Method

It applies with buoys placed along the river, which have fitted sensors to measure the series of movement around them. The buoys are floating on the surface and can provide some indication about the surface current. At the same time, these may not be that precise as the other methods to trace the full complexity of the water current, particularly related to the variation in velocity along different depths.

Among these, the ADCP current profiler is considered a much more advanced and efficient technique of measurement for the water current of the Juruena River.

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

The ADCPs work on the Doppler principle. When an ADCP flow meter sends out an acoustic signal into the water, the sound waves travel in the water and interact with the moving water particles. Since the water particles are in motion, the reflected sound waves return with changed frequency due to the Doppler effect.

If the water particles are moving towards the ADCP meter, the reflected wave frequency is higher than the emitted one. On the contrary, if the water particles are moving away from the ADCP, the frequency of the reflected wave would be lower. Precise measurement of this change in frequency gives the ADCP an exact calculation of the velocity at the different depths.

The ADCP profiler then combines these individual velocity measurements at various depths to create a complete profile of the water current. This allows for a detailed understanding of how the water is flowing not only at the surface but also throughout the vertical section of the river.

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

For high-quality measurement of Juruena River currents, the equipment has to possess the following characteristics.

The high material reliability of the equipment is one of the qualities. It should be made in such a way that it can resist the heavy conditions of the river environment. This includes being exposed to water, sediment, and various temperatures. Variable flow and, at times, the presence of debris like fallen trees and branches during high flows in the Juruena River calls for durable equipment.

Besides, small size, light weight, and low power consumption are desirable. In this way, it would be easier to manipulate and deploy the device due to its compact and lightweight feature, especially in a far-flung and most difficult area of the Amazon rainforest. Low power consumption guarantees that the equipment operates for a long period without frequent battery replacements or access to continuous power.

Cost-effectiveness is a key consideration. The lower the cost, the more measurement equipment can be deployed to monitor the river more extensively.

In regard to casing of the ADCP meter, titanium alloy would be an ideal material. The resistance to corrosion is high in Titanium alloy, which is so critical when dealing with water bodies like the Juruena River, where there will be constant contact of the equipment with water, which may contain corrosive elements. It is strong, durable, and able to withstand physical impacts and the pressure changes that may occur at deployment and operation. Besides, the density of titanium alloy is relatively low; therefore, it helps to achieve the goal of lightening the equipment as a whole.

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

To choose the right equipment for measuring the current of the Juruena River, several factors have to be considered.

Based on the Purpose of Use

If the intention is to measure the horizontal cross-section of the river current, a horizontal ADCP flow meter would be the appropriate choice. HADCPs are designed to provide accurate measurements of the water flow in the horizontal plane, which is useful for understanding the overall movement of water across a particular section of the river.

If the purpose is to measure the vertical cross-section of the river current, one should opt for a vertical ADCP current profiler. Vertical ADCPs can measure the exact velocity of the water at different depths, providing the profile of how the water is flowing vertically within the river.

Based on the Frequency

The choice of frequency, though, depends on water depth in the Juruena River. Water up to 70 meters may find a 600 kHz ADCP quite sufficient normally. The 600 kHz has good resolution and a more accurate measurement for relatively shallower waters.

For deeper waters, such as those exceeding 70 meters up to around 110 meters, a 300 kHz ADCP is 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 well - known 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 Juruena 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.