ADCP in Paraná River Flood Management

1. Where does the Paraná River flow?

The Paraná River is one of the most important rivers in South America. It passes through Brazil, Paraguay, and Argentina.

Originating from the highlands of Southern Brazil, it flows for a long distance through vast and varied landscapes. Its upper reaches pass through hilly and forested regions. As the river continues to flow downstream, it enters great expanses of plains and farmland. The river is a key transportation route, enabling transportation both for goods and passengers. It supplies water for large-scale farming projects, including irrigation, and it plays a crucial role in the energy domain because along its length, a variety of hydroelectric power plants have been built.

These Paraná River regions have a climate of tropical and subtropical types, with easily distinguished wet and dry seasons. The period between November and March is generally the rainy season in the southern hemisphere, with heavy rainfall. The big volume of rains from the sky, in addition to that reaching the river from its tributaries, may cause sudden huge increases in the water level of the river. In the upper reaches, the mountainous terrain can accelerate runoff, causing the river to swell quickly.

2. What are the reasons for floods in the Paraná River?

Heavy Rainfall and Tributary Input: The most important factor responsible for the flood is the heavy rainfall in the wet season. The catchment area of the Paraná River is very large, and during heavy rainfall, a massive amount of water enters the river. Similarly, there are many tributaries that merge into Paraná, which further adds to the influx of water. The result can take the shape of a sudden rise in the level of water and flood.

Relief: Floodplains and low-lying areas along its course provide space for water to spread out and collect. Thus, these relatively flat plains check the flow of water, and thereby enhance the chance of flooding. Sometimes the confluence of tributaries can further worsen the situation of flooding if a number of tributaries attain high flow simultaneously.

Human - Induced Changes: Human activities such as deforestation in the catchment area can reduce the ability of the forest to intercept and retain rainwater. This leads to increased surface runoff and more water reaching the river quickly. The construction of dams and other water-related infrastructure sometimes has effects unintended by those who built them. For instance, if the reservoir of a dam fills up faster than it should during heavy rainfall, discharge into the downstream areas becomes necessary, adding to the flood.

Acoustic Doppler Current Profiler (ADCP) is highly useful for understanding and managing the Paraná River flow during flood events.

3. How do ADCPs using the Doppler principle work?

ADCPs work according to the Doppler principle. The device emits an acoustic signal into the water. Since the water is in flow, the signal will interact with the moving particles of water. By the time that same acoustic signal is reflected back to the acoustic doppler flow meter, the frequency of the reflected signal will have shifted due to the Doppler effect.

The ADCP measures the differential frequency between the emitted signal and the signal received. Through this frequency shift analysis, it will be able to calculate the velocity of the water at every depth. These devices normally contain several transducers that can send and receive acoustic signals in various directions. This allows them to make a profile of the water velocity across a section of the river.

For example, if the water is flowing towards the ADCP current meter, it will fall onto an already emitted signal with a higher frequency; whereas for water that is flowing away from the ADCP current profiler, the signal falling on would have a lower frequency. Precise measurement of these changes in frequency allows the acoustic doppler velocity meter, upon processing appropriate mathematical algorithms, to execute accurate gauging of the velocity of the water at multiple points within its measurement range.

4. What are the applications of the ADCP in the Paraná River floods?

Velocity Measurement

ADCP is very important during Paraná River flooding events to measure the correct velocity of water flow. It gives continuous velocity data at different depths and locations in the flow, which is real-time. This information would help understand the dynamics of the flood, such as the speed with which the floodwaters will move and in what directions.

Application in Flow Measurements

The ADCP flow meter is also capable of measuring the flow rate of the Paraná River. It will combine the measured water velocities at different points across a section of a river and known cross-sectional area of the river to arrive at the total volume of water passing through a section in every unit time, better known as flow rate. It also serves to provide the overall volume of water that comes with every flood event, which helps in making decisions about flood control and management of water resources.

Application in Sediment Transport Research

Besides flow and velocity measurements, ADCP applies in the studies of sediment transport in the Paraná River during floods. While the water is flowing, it carries sediments. The ADCP profiler can detect changes in the backscattered acoustic signal caused by the presence of sediments. By analyzing these changes, researchers can estimate the amount and movement of sediments, which is important for understanding the long-term evolution of the riverbed and the impact of floods on the river's sedimentary environment.

5. How can the data measured by the ADCP be used in flood warning and risk management of the Paraná River?

Flood Warning

Velocity and Flow Data Monitoring: In real-time, the ADCP obtains velocity and flow data that are continuously monitored. When the water velocity exceeds the measured threshold or when flow rates show considerable increments, this may indicate the approach of a flood peak or possible flooding. With this warning, relevant authorities can take necessary precautions by evacuating people from low-lying areas or strengthening flood defenses.

Water Level Prediction and Warning: Measured flow data, when correlated with historical data on water level and appropriate hydrological model, can be used to predict future water levels. If the predicted water level is expected to exceed the flood warning level, timely warnings can be issued to the public to get ready for the flood.

Risk Management

Water Conservancy Project Scheduling Decision Support: The accurate flow and velocity data provided by the ADCP can help make decisions on the operation of water conservancy projects like dams and sluice facilities. For example, with reference to the measured flow of water, the release from the dam can be regulated to control the water level of the Paraná River to mitigate the impact of floods.

Flood Disaster Assessment and Emergency Response: In the event of a flood, the ADCP-collected data may be applied to determine the intensity of the flood. This would involve information like the area covered by the flood, the velocity of floodwater flow, sediment deposits, among others. Such information would be helpful in designing the emergency response plan and in undertaking post-flood reconstruction and rehabilitation work.

6. What is necessary for high-quality measurement of the Paraná River currents?

High-quality measurement of the currents of the Paraná River involves several aspects. First, the materials used for the equipment should be reliable. The ADCP casing is rather very important. The casing is recommended to be made from a titanium alloy. The high strength of the titanium alloy enables the equipment to resist the pressure and impacts exerted by flowing water in the river, while it is highly resistant to corrosion, which is very important in consideration of the water environment of Paraná River, possibly containing various corrosive substances.

In addition to the reliability about materials, the size and weight of the equipment should be as small and light as possible. This makes the ADCP much easier to install and operate in the various locations along the river, particularly within areas that are difficult to access. Low power consumption is also very important, as this enables the ADCP to continuously run for longer periods of time without necessarily needing battery replacement or interconnection to a power source. Besides that, the equipment cost must be relatively low to make large-scale measurement possible. With a lower cost, more ADCPs can be deployed to measure the current in Paraná River and therefore provide more detailed data for flood management.

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

When choosing the right equipment for current measurement in the Paraná River, several aspects need to be taken into account. Firstly, depending on the type of measurement required, if it is for horizontal cross - section measurement, a Horizontal ADCP (HADCP) should be selected. If it is for vertical cross - section measurement, a Vertical ADCP is the appropriate choice.

Secondly, different frequencies are suitable for different water depths. For instance, a 600 kHz ADCP would be adequate for water within a depth of 70 m. Therefore, if the water depth in the Paraná River is within this range and the measurement requirements match, then a 600 kHz ADCP can be considered. For deeper waters, exceeding 70 m and up to 110 m, a 300 kHz ADCP is more desirable; with this it is possible to get more accurate measurements in such depths.

There are several well-known ADCP brands on the market, including Teledyne RDI, Nortek, and Sontek. But these are rather expensive. In that case, China Sonar PandaADCP is a good choice if cost is a big concern. The material is made of all-titanium alloy, ensuring its durability in the water environment, along with its reliability. What's more, it can deliver an astonishing cost-performance ratio. You can find more about it on its official website: (https://china-sonar.com/)

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