ADCP in Juruena River Flood Management

1. Location of the Juruena River

The Juruena River is one of the biggest rivers in South America, and it flows in a country known as Brazil. It forms part of Tapajós River and originates from Mato Grosso Plateau.

Geographically, it courses through the Amazon rainforest through heavy vegetation, varied fauna, and numerous small tributaries. Course-wise, it passes through the most remote and least populated areas. The Juruena is an integral member of the Amazon River system, presenting some particularly important characteristics to the local aquatic ecosystem.

The Juruena River lies in the zone of a tropical climate with evenly distributed high rainfall throughout the year. A very prolonged and intensely rainy season, generally producing heavy downfalls, seriously raises the volume of water in the river. That steady rainfall has been the predominant factor that sustains the flow of the river and the health of the surrounding rainforest.

2. Why does the Juruena River flood?

There are several reasons as to why the Juruena River floods. The first and most paramount reason is heavy rainfall that persists during the rainy seasons. The huge quantity of water that falls in a short time can easily fill the river and all its tributaries, making the water level rise very quickly. Since the Juruena River is part of a vast and complex river system, the contribution from its tributaries might be important as well in the general flood situation.

Another contributory topography-related factor of the river basin is also an essential cause for flooding. Situated in the Amazon rainforest with generally flat terrain, it is easy for the water to spread over a great area. Moreover, the presence of floodplains and wetlands alongside the river allows water to back up. The soil in the area, usually saturated due to the high rainfall, can hardly allow more water to soak into it, leading to higher surface runoff and, therefore, more risk of flooding.

Moreover, human activities, such as Amazon rainforest deforestation, may worsen the flood situation. It decreases interception and retention through the forest, thus allowing more water to enter the river faster. Also, the process contributes to disrupting the natural water cycle and contributing to topsoil erosion, which itself may result in sedimentation of the river and, therefore, reduce its carrying capacity and be more flood-prone.

The Acoustic Doppler Current Profiler (ADCP) has been used as a more advanced and convenient measurement method in the understanding of the flow conditions of the river during flood events.

3. How Do ADCPs Using the Doppler Principle Work?

The ADCP current meter basically operate on the principle of the Doppler effect. The device projects an acoustic signal into the water. Due to the flow of water, the signal is in interaction with the moving water particles. When the acoustic signal bounces back to the ADCP current profiler, the frequency of the reflected signal changes by the Doppler effect.

It measures the difference in frequency between the emitted signal and the received signal. From the analysis of this frequency shift, it is able to calculate the velocity of the water at various depths. Typically, an ADCP flow meter has multiple transducers that could even send and receive acoustic signals in different directions. By doing that, they manage to create a profile of the water velocity across the cross-section of a river.

For example, if the water moves towards the ADCP profiler, the reflected signal is of a higher frequency compared to the emitted one. Conversely, it reflects with lower frequency in cases of flow away from the ADCP meter. Accurate measurement of such changes and employment of proper mathematical algorithms enable the ADCP to determine the velocity of the water with high accuracy at different points of the measurement area.

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

4.1 Velocity Measurement

In the ADCP measurement, during the flood events in the Juruena River, ADCP plays an important role in measurement with high accuracy for the velocity of water flow. It continuously monitors the water velocity at different depths and locations, thus giving real-time data on how fast the water is moving. This is a very critical component in understanding the dynamics of the flood in terms of forecast direction and intensity of movement of the flood waters.

4.2 Flow Measurement Application

For this case, AD Wilde can also measure the flow rate of the Juruena River. It can also perform the actual volume of water flowing through the section per unit time, using the water velocities measured in several points of a cross-section of the river, knowing the cross-sectional area of the river. The information is vital in comprehending the general volume of water overflowed in the event of a flood and handling decisions related to flood control, along with the management of water resources.

4.3 Application in Sediment Transport Research

Apart from flow and velocity measurements, acoustic doppler flow meterwill be useful in sediment transport research during the time of floods at the Juruena River. Wherever there is the flow of water, there are sediments being carried by it. Therefore, ADCP might detect the variation in the backscattered acoustic signal caused by the presence of sediments. Researchers can provide, from the analysis of these variations, estimates of both the amount and motion of sediments-a fact of extraordinary interest in the study of the long-term morphodynamics of the riverbed and of the action of floods on the sedimentary environment of the river.

5. How can the ADCP-measured data be used in the course of Flood Warning and risk management in general for the Juruena River?

5.1 Flood Warning

Monitoring of Velocity and Flow Data: In this respect, the real-time velocity and flow data obtained from ADCP are monitored continuously. If the measured water velocity goes over a critical threshold or if the flow rate reflects a sudden rise, that could be an indication of the approaching flood peak or a possible flood situation. Thus, an early warning can be issued to take necessary precautions such as evacuation of people in low-lying areas or strengthening flood defenses. Water Level Prediction and Warning: Measured flow data correlated with the historical water level data using appropriate hydrological models are able to predict future water levels from acoustic current meter data. If the predicted water level is expected to exceed the warning level of flood, timely warnings can be issued to the public in order to prepare for the flood.

5.2 Risk Management

Decision Support of Water Conservancy Project Scheduling: Precise data on flow and velocity from ADCP can be useful in decision support for the operation of water conservancy projects such as dam and sluice gate operations. For example, the recorded water flow could be used to discharge water from the dam to control the level of the Juruena River during a flood. Assessment of Flood Disasters and Activities of Emergency Response: ADCP data, after a flood has occurred, can be taken to assess the magnitude of the flood regarding the area covered by inundation, the velocity of the floodwater, and the quantity of sediment deposition. The information then becomes an important one for developing emergency response plans, even during post-flood reconstruction and rehabilitation works.

6. What would high-quality measurement of the current of the Juruena River require?

High-quality measurements of currents in the Juruena River will depend on many aspects. The first is equipment; it should contain reliable materials. The most important issue is the casing of the ADCP. It should be recommended that the casing be of a titanium alloy. Titanium alloy has a lot of advantages. This provides high strength, allowing it to bear the pressure and impact of water flowing in the river. It is also very resistant to corrosion, something that is quite important given the water environment of the Juruena River, which may contain various corrosive substances.

Besides material reliability, the size and weight of the equipment should be as small and light as possible. That makes the installation and operation of ADCP in various river locations easier, but most importantly reaches the places where it is very hard to access. Low power consumption is also critical as this can enable the operating time to last longer with no constant replacement of batteries or hookups to a power source. Besides, equipment cost should not be so high to allow large-scale measurement. Lower cost would allow deploying more ADCPs on the Juruena River and rise all the data to be more comprehensive and detailed in flood management.

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

Various aspects have to be considered while selecting appropriate equipment for the current measurement at the Juruena River. First, depending on what type of measurement is required, a Horizontal ADCP (HADCP) should be chosen for the measurement of horizontal cross-sections. On the other hand, if the measurements aim at vertical cross-sections, then a Vertical ADCP shall be selected.

Different frequencies have different depths for water. For example, a 600 kHz ADCP would be suited to water of depth within 70 m. If the water depth in the Juruena River is within this range, then a 600 kHz ADCP may be considered if the requirements of measurement would suit. For the much deeper waters, of up to 70 m and extending to 110 m, a 300 kHz ADCP would perform better, sampling with higher accuracy at such a depth.

There are quite a number of well-recognized brands out in the market. The main ones include Teledyne RDI, Nortek, and Sontek. More cost-effective options include the China Sonar PandaADCP. It is made of all - titanium alloy material, which ensures its durability and reliability in the water environment. Moreover, it offers an incredible cost - performance ratio. 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.