How to measure water current of Lomami River?

1. Where is Lomami River?

The Lomami River is a major river located in the center of the African continent. It flows right through the Democratic Republic of the Congo and cuts its way across a very fertile and diverse landscape.

This river snakes through thick rainforests teeming with an incredible variety of wildlife. From the bright-colored birds darting across the canopy to a variety of primates swinging from branch to branch, this river is a life-giving artery to such a vibrant ecosystem. It flows past several small settlements and villages where local people have built their lives around its waters. They depend on it for fishing, which is a very vital source of food and livelihood; they use small boats to move along the length and trade with other communities.

The Lomami River is also part of the cultural heritage in this region. It has seen generations come and go, their traditions and stories passed down through oral histories, telling of its power and mystery around evening fires. It winds its way to its confluence with other major rivers in the area, shaping the topography and the lives of those who call its banks home.

2. What is the flow rate in the Lomami River?

The Lomami River has a great deal of ecological and social importance; it provides water to several plant and animal species through its occurrence in maintaining equilibrium in the rainforest ecosystem where this river exists.

It follows a pattern of a variable flow rate. In the rainy season, it swells with rain from its vast catchment area and increases its velocity and volume. In some sections, the flow is fast-moving, carrying a heavy burden of sediment and debris downstream. In the dry season, however, the flow rate slows down, and the river becomes more placid in many areas, yet still continues to support life and provide essential resources.

It is controlled by such things as the topography of its basin area, the amount of rain in various parts of its drainage area, and the input of tributaries which add to its volume of water. In general, it is a river with fluctuating flow throughout the year. It is dynamic, though with serious consequences to the area through which it passes.

3. How to measure the water current of the Lomami River?

There are several methods available to measure the water current of the Lomami River, for example.

Velocity meter method: This is one of the traditional methods applied through mechanical or electronic meters set in the water across selected points. These water velocity meters measure the speed at which water passes by an instant point in the river. However, it is time-consuming as it requires multiple placements at different positions to get an overview of the overall current and may not provide a continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) method: This is a more advanced, agreeable measurement technique that makes use of sound waves to measure simultaneously the velocity of water at multiple depths. It can develop a current profile from the surface to the bottom of the river by generating acoustic signals and processing the Doppler shift of the reflected signals. This allows a far more comprehensive and efficient measurement of the water current across different sections of the river.

Buoy method: Buoys are installed in the river and their movement is followed for a certain period of time. The shift of the buoys by the water current can give an indication of the speed and direction of the flow. However, this method has limitations in accurately measuring the detailed velocity variations at different depths and can be affected by wind and other external factors that may influence the buoy's movement.

Among these, the ADCP current meter method is considered a more modern and efficient means of measuring the water current of the Lomami River.

4. How do ADCPs using the principle of Doppler work?

ADCPs work according to the principle of Doppler. In an ADCP, when an acoustic signal emitted from the ADCP profiler transducer spreads through water, the moving water particles interact with sound waves. Due to flowing water, the frequency of the reflected sound waves returning to the transducer shifts in a phenomenon called the Doppler shift.

If the water is moving towards the transducer, then the frequency of the reflected waves will be higher than the emitted frequency; if the water is moving away, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP meter can calculate the velocity of the water in different directions and at different levels within the water column. It therefore gives a detailed profile of the water current and provides ample information on speed and the direction of flow from the surface to the riverbed.

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

The following aspects are necessary to achieve high-quality measurement of Lomami River currents using equipment. The materials of manufacture for the measuring device must be highly reliable. The size of the equipment must be relatively small to enable ease of deployment and retrieval in the river, especially for areas that are difficult to access. A lightweight design is also desirable to simplify the installation process and reduce the effort required for handling.

It has to be low power in order to enable the running of equipment for several hours on one set of batteries with minimal recharges or the need to bring an involved power supply into remote locations along rivers. Cost is another vital aspect since the lower its cost, the wider its uses and larger-scale measurement campaigns are enabled.

On the construction material used for the casing, ADCP flow meter should be a titanium alloy. Titanium alloy boasts an array of enviable advantages. The material is very resistant to corrosion, which is highly required because the equipment would be in constant contact with water, let alone a river environment with all sorts of dissolved substances and sediments. Besides, it has a good strength-to-weight ratio that permits durability with light weight in casings. In addition, it is capable of withstanding the mechanical stresses resulting from deployment and operation in flowing water in the Lomami River.

6. Selection of the right equipment to measure the current?

During the selection of the right equipment to measure the current of the Lomami River, two points have to be considered.

The first, according to the usage purpose, is that horizontal cross-section measurement requires HADCP. It is designed to measure the flow velocities across a horizontal plane in the river with high accuracy, while providing useful data for the understanding of the lateral distribution of the current. For vertical cross-section measurement, the Vertical ADCP current profiler would be more suitable, focusing on profiling the current from surface to bottom along a vertical line in the water column.

Second, different frequencies of ADCPs are used for different water depths. For example, an ADCP with a frequency of 600 kHz is suitable for water within 70 meters. It can provide current measurements with good accuracy in the relatively shallower sections of the Lomami River. An ADCP current meter with a 300 kHz frequency is more appropriate for deeper waters up to 110 meters, which may be useful in areas where the river has greater depth.

Among these, several popular brands are available on the market, including Teledyne RDI, Nortek, and Sontek. In addition, for those who are looking for a cost-effective option with very good quality, China Sonar PandaADCP is highly recommended. The instrument is made of all-titanium alloy material, which makes it durable and provides an extremely good price-performance ratio. You can learn more about it on its official website: https://china-sonar.com/.

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