How to Measure Water Current of the Negro River?

1. Where is the Negro River?

The Negro River is a big river in South America, actually in the Amazon Basin. It is considered the largest tributary of the Amazon River. The headwaters are in the highlands of Colombia and Venezuela, from where it runs along Brazil.

This Negro River flows through every imaginable kind of landscape on its upper course: piercing through thick rainforests with heavy canopies full of fantastic varieties of flora and fauna, with tall trees lining both banks of the river while carrying a host of peculiar species in its waters. In its waters, the pink river dolphins swim gracefully; it's a haven for different species of fish, caimans, and turtles, while the surrounding rainforest is home to many birds, monkeys, and other mammals.

As the Negro winds its way down through Brazil, it is integral to the ecosystem and the people who depend on its route. It's transportation: boats and canoes ply the water, connecting far-flung communities. This river supplies the communities along its banks with drinking water, fishing, and irrigation.

2. What is the Flow Rate of the Negro River like?

The Negro River is one river that experiences a large variation in flow rates, further dependent on the vastly elaborate hydrological cycle of the Amazon. During its rainy season-which ranges between December and May in the Amazon region-heavy rainfall in the catchment area creates a swollen Negro River. Its flow rate can increase by as much as one order of magnitude, and the current becomes very strong. This results in the flooding of major areas of the floodplain into the wetland ecosystem so important to many species.

During the dry season, it starts from June to November, the flow rate is reduced. The width of the river shrinks and so does the level of its water. At this period, the river still has a considerable flow due to the base flow coming from the groundwater sources and a few minor tributaries. The average flow rate varies along the various parts of the river. It can be relatively fast towards the head due to the higher gradient, while during its lower end and when it receives a flat terrain of the flood plain area, the flow is retarded.

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

Water current of the Negro River could be measured in several ways.

Traditional Methods

Float Method: The traditional, uncomplicated way of estimating the current in water is by a float. A buoyant thingy-a block of wood or even a plastic bottle-is set free in the river. An approximation of the speed at surface current can be obtained by measuring the time taken for the float to travel a known distance. This method has its limitations. Wind, waves, and float shape could all introduce errors, and it gives only the surface current-in other words, it does not give the current of at various depths.

Current Meters: These are either mechanical or electronic and can be used to measure the water speed of one point. These meters are placed in the water at a certain depth and measure the speed of the water passing through them. They can give more detailed measurements than the float method at that one point in the water column. However, they are limited to that one depth and do not give a complete picture of the current profile throughout the water column.

Advanced Technique: Acoustic Doppler Current Profiler (ADCP) ，ADCP current meter represent a more effective and efficient technique in measuring the Negro River water current.

3.1 The operating principle of ADCPs using the Doppler Principle

Principle of Operation ADCP current profiler is based on the principle of the Doppler effect. An acoustic pulse is emitted into the water from the device. These pulses interact with particles suspended in the water and other materials in the water, such as sediment, plankton, and small debris. When the water moves, so does the frequency of the reflected acoustic signal.

This frequency shift is measured by the ADCP doppler and, using the Doppler formula, the ADCP flow meter calculates the velocity of the water at various depths. By transmitting pulses in several directions and on different frequencies, the ADCP meter creates a very detailed profile of the water current throughout the water column. This will give a far more complete understanding of the structure of the current in a river compared to traditional methods that measure either at or near the surface or at one point in the water column.

3.2 What is required for a high-quality measurement of Negro river currents?

To have a high quality measurement for the Negro river currents, it requires that the equipment used must be very reliable. The environment of the Amazon rainforest is notorious for adverse conditions with its high humidity, heavy rainfall, and potential harmfulness brought about by floating debris; hence, the measuring devices need to be able to resist such challenges.

The equipment also has to be compact and of low weight. This is so crucial, which ensures ease of deployment, especially in some remote areas across the river that may be accessible only by boat or on foot through the rainforest. It shall have low power consumption to ensure that the equipment operates for an extended period without necessarily changing batteries or looking for external sources of power. Other important factors are cost-effectiveness, mainly in cases when large-scale or long-term measurements of the dynamics should be monitored.

One big positive side is that the casing of ADCP profiler is manufactured from titanium alloy. An alloy of titanium has an exceptional resistance to corrosive processes, which is extremely important in the water-environment of the Negro River. The constant water immersion, with the presence of various chemicals and sediments, acts as a catalyst in the corrosion process of other materials. It is also tough enough to handle stresses that may arise due to physical forces from the river current and possible impacts from floating logs or any other moving debris. Being lightweight, it is easy to install and transport.

3.2 How to Choose the Right Equipment for Current Measurement?

Equipment choice in measuring the current of the Negro River is based on specific measurement requirements.

Horizontal Measurements: This measurement can be taken across a section of the river using a horizontal ADCP-HADCP. It makes a wide view of the current flow in a horizontal plane, useful for understanding the overall flow patterns of the river. This is particularly essential in respect to studies on the transport of water and sediments across the stream and the effect it has on navigation and the distribution of nutrients.

For Vertical Profile Measurements: In the case of vertical profile measurements of the current, a vertical ADCP is more appropriate. It can provide detailed information about the speed of water at different depths, reflecting in the stratification and mixing of the water column. It turns very relevant to be able to understand the distribution of oxygen, temperature, and other properties within the water and the behavior of aquatic organisms.

Frequency Selection: For frequency selection, in the case of fairly shallower reaches of the Negro River, where the depth may reach as high as approximately 70 m, a 600 kHz ADCP would be appropriate. In reaches deeper than this but up to approximately 110 m, a 300 kHz ADCP is best. Choice of frequency is tied to water depth and resolution in the current profile desired.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with good quality, the ChinaSonar PandaADCP is a great choice. It is made of all - titanium alloy, providing durability and resistance to the Negro River's environment. It also offers an excellent price - performance ratio. You can visit https://china-sonar.com/ for more information.

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