How to measure the water current of Purus River?

1. Where is Purus River?

The Purus River is one of the major water bodies in South America. It meanders through the heart of the Amazon rainforest - a region widely regarded for its incomparable natural beauty and ecological importance.

The Purus River twists and turns, carving its way through thick tropical forests, rich in life with varied landscapes. An amazing variety of flora and fauna populates this area: tall trees, bright orchids, and rare medicinal herbs along its shores, while colored macaws, playful monkeys, and elusive jaguars populate the surrounding wilds.

The river is also a host to various indigenous communities who have had generational time with nature. Most communities that depend on survival benefits from the Purus River through fishing, transportation, and water can be found in the area.

Besides being a natural wonder, the Purus River is a cultural treasure that speaks to the variety of heritage and tradition indigenous to the people living in this region. Its waters are identified with life and vitality since they link several ecosystems and communities.

2. What is the flow rate of the Purus river like?

The Purus River runs variably within the year. In the usual process, from November to April, much rain is received, and because of abundant rainfall in the rainy season, the volume of water increases with a very high flow rate. Its increased water volume can cause the river to overflow its banks and flood the surrounding areas.

By contrast, the dry season, which includes the months between May and October, sees considerably lesser flow rates in the Purus River. Its water level goes down, and large areas of the river may be shallow and hence easier to cross.

The Purus River is a catchment area that underlies flow variability, on topography and climate, as far as the presence of tributaries is concerned. In fact, the river crosses the Amazon rainforest, and thus its characteristic flow passes through topographically diverse terrain with abundant rainfall.

On average, the flow rate of the Purus River varies from several thousands of cubic meters per second during the rainy season to a few hundred cubic meters per second during the dry season. But these figures can vary depending on the particular location within the river and the time of year.

3. How to measure water current of Purus River?

The measurement of the current of the Purus River is a matter of great importance, as it aids in understanding the hydrological nature and various applications related to navigation, flood control, and environmental monitoring. There are a few traditional general methods for measuring the current, each of which has its advantages and disadvantages. Traditional measurement of river currents has commonly involved the use of current meters. Current meters are those meters whose principles of operation revolve around the rotor or propeller movement to measure the velocity of flow. They are deployed in a river either by suspension from a bridge or by boat that will drop the meters at various locations.

Another traditional way is by using floats. The floats can be dropped into the river and their movements monitored to obtain an estimation of the speed of the water current. This technique, to say the least, is somewhat simple and cheap but not that accurate.

Modern methods

Advanced technologies have been developed in recent years for the measurement of river currents. One of the advanced technologies developed is called acoustic Doppler current profilers, commonly referred to as ADCP flow meter. The working principle of ADCP profiler follows the Doppler principle for the measurement of velocity in water flow at different levels of depth in the river. They can provide a detailed flow field and can be used both for horizontal and vertical profiling.

ADCP: An advanced, convenient measurement method

They have some advantages in comparison with traditional methods. They can measure currents from very shallow to quite deep, and velocities, even with real-time data. Bottom-mounted ADCP can be reasonably easily deployed and operate in a typical range of environments such as estuaries, rivers, and regional seas.

3.1 Principles of the current measurement by Doppler principle using ADCP

In operation, Acoustic Doppler Current Profiler(ADCP) work by emitting sound waves into the water and their reflection indicates the frequency shift. This shift in frequency is a factor of the actual movement of the water particles, which is again proportional to the velocity; hence, by analyzing the frequency shift, the ADCP determines the speed at which water flow is taking place at different depths.

ADP consists of a transducer array that emits and receives sound waves. The transducer array is mounted on frames or vessels and oriented to measure horizontal and vertical currents. It also contains a data processing unit to process the received signals thereafter the velocity profiles are calculated.

3.2 What is needed for high-quality measurement of Purus river currents?

There are various factors to consider in conducting a high-quality measurement of Purus River currents. First, the reliability of the measurement equipment has to be considered. The equipment is supposed to be strong enough to bear up with the harsh environmental conditions of the river, such as strong currents, fluctuating water levels, and high temperatures.

Besides, equipment should be compact in size, lightweight, low in power consumption, for easy deployment without giving a large impact to the environmental impact. Moreover, the cost of the equipment has to be low to make measurements on a large scale.

Use of a casing made of titanium alloy: benefits

Basically, the casings for acoustic doppler flow meter could be made of titanium alloy to meet these needs. Titanium alloy is also a very strong but lightweight material, and it is completely resistant to corrosion. It would be capable of withstanding the river's aggressiveness and giving good protection to the sensitive parts of the ADCP current meter.

The excellent heat conductivity of the metal alloy results in dissipation of heat and conveys no case of overheating in the equipment. The avoidance of errors in measurement is necessary to maintain its accuracy and reliability.

3.3 How to Choose the right equipment for current measurement?

Several variables would come into play in choosing the equipment to perform the measurement of the Purus River currents. First is the purpose or intended use of the measurement. If the measurement is for horizontal profiling in the river, an HADCP would be most suited. HADCP are specifically designed to measure the current velocity in a horizontal plane and would yield valuable details on the flow field.

If it is an instrument for vertical profile measurement, a vertical ADCP will be more suitable. Vertical ADCP operate to record current velocity measured at every different depth of the river and can provide information about the vertical structure of the flow.

Another consideration is the frequency of the ADCP itself. In fact, different frequencies are suited to different water depths. For example, a 600 kHz ADCP would be suitable for water as deep as 70 meters, while the 300 kHz would go as deep as 110 meters.

Conclusion

The measurement of the water current of the Purus River is an important task when it comes to understanding the hydrological features of this river and for numerous purposes. The ADCP represent one of the most powerful and handy means in river current measurements, obtaining real-time data with highly detailed knowledge about the flow field. In choosing an ADCP current profiler to measure the current of the Purus River, factors such as reliability, size, weight, power consumption, cost, and frequency should be considered. This enables us to make quality measurements by choosing appropriate equipment and then using it correctly to better understand and manage this important waterway.

To end, let us enumerate some of the leading brands in ADCP doppler available in the market. Teledyne RDI, Nortek, and Sontek are the better-known brands with a wide range of ADCP products. However, for those who would want cost-effectiveness and quality with all titanium alloy casing at incredible value for money, there is China Sonar's PandaADCP. You can visit their website at https://china-sonar.com.

Following is a table of some of the popular brands and models of ADCP instrument.