How to Measure Water Current of Iguaçu River?

1. Where is Iguaçu River?

The Iguaçu River is an extraordinary river situated in South America. It constitutes the border between Brazil and Argentina, with a touch of Paraguay. It originates from the Serra do Mar mountains in Brazil, further zigzagging through rainforests and different landscapes.

This river is a marvelous piece of nature, home to an incredible variety of wildlife, including the surrounding rainforests full of jaguars and capybaras; the birdlife is also second to none. It gives way to various important cities and tourist destinations along its course, with Foz do Iguaçu in Brazil and Puerto Iguazú in Argentina being the better-known ones because of their proximity to Iguaçu Falls. These falls constitute one of the most breathtaking natural wonders of the world, as a huge curtain of water thunders downwards, creating a scene enveloped in mist and inspiring a feeling of awe.

Iguaçu is not only a tourist sport but also an important resource within the communities. It provides water for agriculture since the fertile plains along its sides are used for crop cultivation, especially soybeans and sugarcane. Fishing is another important activity; different kinds of fish are found in this river. Culturally, it holds a special place in the hearts of the people. The river is closely related to the indigenous tribes in the area and forms a part of their folklore and traditions.

2. What is the nature of the Iguaçu River flow?

The Iguaçu River's flow rate largely depends on various factors. For instance, during the rainy months between November and March of each year in this region, the river will have much higher flows. As a result of the heavy rainfall in the catchment area, the water level increases by a great margin, with its flow velocity being relatively high. In the process, the river may carry a lot of sediment and debris that might affect the downstream ecosystems and the general appearance of Iguaçu Falls.

During the dry period of the year, from April to October, the flow rate decreases. The river still flows steadily, but in a much more docile manner than in the wet season. Careful attention is paid to the flow because this is important for ensuring the water supply for agriculture and domestic use, as well as the ecological balance of the river and its surroundings. This average flow rate is determined by the intensity of rainfall in the upstream areas, the relief of the drainage area, and the contribution efficiency of the tributaries.

3. How to measure water current of Iguaçu River?

There are various ways to measure the water current of the Iguaçu River:

Velocity Meter Method: The conventional technique makes use of mechanical or electrical velocity meters. They are set in the water at certain positions, by which the speed of water passing is measured. This approach, however, needs to be very carefully positioned at various locations and depths to grasp a general view of the current. It can be very time-consuming and may not necessarily yield a continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method: This is an advanced and quicker way of measuring water current. It can measure simultaneously the velocity of water at different depths using sound waves. It emits acoustic signals and analyzes the Doppler shift of the reflected signals to produce a very detailed profile of the current from the surface to the riverbed. This allows for accurate and comprehensive measurement of the water current in different sections of the river.

Buoy Method: This involves placing buoys in the river and monitoring their movements over some time. The displacement of the buoys by water current provides the speed and direction of the flow. This method has many limitations. It cannot give the actual velocity at different depths and is usually affected by some external factors such as wind and waves, which could affect the movement of the buoys.

Among these methods, the ADCP method is more modern and convenient for the measurement of the water current of the Iguaçu River.

4. How do Doppler principle-based ADCPs work?

ADCPs work on the principle of the Doppler effect. An acoustic signal emitted from the ADCP transducer into the water is scattered by the moving water particles. Due to the flow of water, the frequency of the reflected sound waves back to the transducer changes, a phenomenon known as the Doppler shift.

If the water is moving towards the transducer, the frequency of the reflected waves will be higher than the emitted frequency. If the water is moving away from the transducer, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP is able to calculate the velocity of the water in various directions and at different levels within the water column. This enables it to create a very accurate profile of the water current, thereby availing much-needed information on the speed and direction of flow from the surface down to the riverbed.

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

For high - quality measurement of the Iguaçu River currents, the equipment should have certain characteristics. The materials used in its construction need to be reliable to ensure accurate and consistent measurements. A small size is beneficial as it allows for easier deployment and retrieval in the river, especially in areas with difficult access. The equipment should also be lightweight to simplify the installation process and reduce the effort required for handling.

It ensures that the equipment operates with a low power consumption, for long periods, without any complex power supply setup to make it possible, avoiding battery replacements. Cost-effectiveness is another important criterion in its construction; more widespread use and larger-scale measurement campaigns are possible because of cost-effectiveness.

The casing for the ADCP will be in titanium alloy. A Titanium alloy possesses many advantages. The material is highly resistant to corrosion, which is so important, as the equipment is in continuous contact with water that might have many minerals, sediments, and pollutants. It also has a good strength-to-weight ratio that allows for a strong but lightweight casing. Lastly, it will be able to bear the mechanical stresses of deployment and operation in flowing water.

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

When choosing the right equipment for the Iguaçu River's current measurement, two main aspects should be considered:

Depending on the usage purpose, the Horizontal ADCP (HADCP) is used for a horizontal cross-section measurement. It is designed to measure the flow velocities across a horizontal plane in the river with high accuracy for the purpose of understanding the lateral distribution of the current. In the case of vertical cross-section measurement, the Vertical ADCP would be more appropriate because it focuses on profiling the current from the surface to the bottom along a vertical line in the water column.

The ADCPs have different frequencies, each of which is suitable for a different depth of water. For instance, an ADCP with a frequency of 600 kHz is suitable for water within 70 m in depth. Thus, it provides the best measurements of current in relatively shallow parts of the Iguaçu River. An ADCP with a frequency of 300 kHz is more appropriate for waters with up to 110 m of depth, useful in areas where the river has greater depth.

There are well - known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with good quality, the China Sonar ​PandaADCP is highly recommended. It is made of all - titanium alloy material and offers an incredible price - performance ratio. You can find out more about it on its website: ​https://china-sonar.com/.

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