How to Measure Water Current of the Tapajós River?

1. Where is Tapajós River?

The Tapajós River is a great and beautiful river right in the heart of the Amazon rainforest, Brazil. This is a main affluent of the Amazon River. The Tapajós originates from the Brazilian Highlands and extends for about 1,240 miles or 2,000 kilometers.

This is an important artery for the Amazonian ecosystem and the local communities. Linear rainforests with highly diverse flora and fauna line its banks. From the well-known Brazil nut trees down to parrots in all their colors and even to the cunning jaguar, the Tapajós River and all its vicinities maintain very great biodiversity. It also cuts through lands that belong to indigenous communities-that is, the native tribes that have a close rapport with the water, such as the Munduruku. Transportation, fishing, and even life-sustaining water are just but a few of today's realities that depend on this river.

The Tapajós estuary is where this river flows into the Amazon River. As a result of the one-way mixture of waters in this estuary, there is a zone with very particular conditions that makes it indispensable for the spawning and growth of many fish species. Its flow carves out the landscape into islands, sandbars, and floodplains that are all integral parts of the ecological complexity of the Amazon region.

2. What is the Tapajós River Like in Flow Rate?

In the Amazon basin, the Tapajós River has its meaning. Generally, the nature of the flow is controlled by the seasonal rainfall in Amazons. In the wet season, from December to May, there is an evident and remarkable increase in flow. The average discharge in this period can be quite high, with estimates ranging from tens of thousands of cubic meters per second.

During the dry season, Tapajós reduces its flow. With a big watershed and, moreover, underground sources of water feeding it continuously, the volume is still quite big. Its flow would also be influenced by lighter tributaries around that add to its volume and flow regime.

This flow is essential to the maintenance of health in the Amazon rainforest and other ecosystems that are connected with it. Its flow is crucial in the distribution of nutrients, availability of water to various plants and animals, and control of temperature and humidity.

3. How to Measure Water Current of Tapajós River?

The measuring of the water current of the Tapajós River can be carried out in several ways. The traditional techniques are the use of floats and mechanical current meters. The floats can be placed in the river and, knowing the distance traveled and the time used, an approximation of the speed of the superficial current is obtained. Mechanical current meters are placed directly in the water, therefore measuring the speed in only one point.

However, Acoustic Doppler Current Profilers can do the measurement of water current more effectively. ADCP current meter is capable of providing a much larger coverage of the river's current profile.

3.1 How do ADCPs Using the Doppler Principle Work?

Working principle: The Acoustic Doppler Current Profiler(ADCP) work on the principle of the Doppler effect. They shoot acoustic pulses into the water. Interaction of these pulses with the particles of moving water causes a change in the frequency of reflected pulses. Thus, according to this frequency shift, it calculates the speed of water at different depths.

Various transducers projected in the ADCP current profiler send acoustic signals. Those transducers can measure the horizontal and vertical components of the water flow. It can therefore make a three-dimensional map of the water current, which is very useful because the current in the Tapajós River has a very complex flow pattern.

3.2 What's Needed for High - Quality Measurement of Tapajós River Currents?

Quality of equipment material is vital in achieving high-quality measurements of Tapajós River currents. The casing of the ADCP doppler should be of a reliable nature; a very suitable material being titanium alloy.

Some of the benefits accrued through the use of a titanium alloy are listed below. First, it is lightweight and, therefore, easy to handle and deploy at most remote and difficult locations along the Tapajós River. It is also resistant to corrosion. Considering the chemical makeup of the water in the Tapajós River and the humid tropical environment, corrosion-resistant properties ensue with longevity and accuracy for the ADCP flow meter.

In addition, for extensive measurements along the Tapajós River, the ADCP should have low power consumption and low cost. Thus, wider and more frequent utilization will not incur a lot of energy and financial costs. Due to its long operational time, the low-power-consumption ADCP profiler is ideal for the long-term monitoring of the current of the river.

3.3 How to Choose the Right Equipment for Current Measurement?

According to the intended usage, selection of the appropriate ADCP meter for measurement in the Tapajós River should be considered. If horizontal flow over a section of the river is being considered, a Horizontal Acoustic Doppler Current Profiler-HADCP may apply. The HADCP is suited for measuring the horizontal velocity components of the water current.

The VADCP is the better choice for vertical flow profile measurements. VADCPs are set up to be able to measure the velocity of the water at various depths along a vertical line in the river.

In terms of frequency, for more shallow areas of the Tapajós River, this capacity of the 600 kHz ADCP will extend up to approximately 70 meters. Where there is the need to move between very deep sections, the 300 kHz ADCP shall do well and consistently work to a depth about 110 meters.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. But for a cost - effective option with good quality, China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material and offers an excellent cost - performance ratio. You can find more information on their website: https://china-sonar.com/.

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