How to Measure Water Current of the Magdalena River?

1. Location of the Magdalena River

The Magdalena River is a major and remarkable watercourse crossing the Republic of Colombia. It has its origin in the Andean highlands, precisely within the Huila Department. From this place, it winds its course to the north while passing through different geographies and regions.

Along its course, it passes many cities and towns that have prospered from it. Cities such as Honda and Cartagena are so attached to the Magdalena River. It is a vital means of transport in the country; it moves goods, too, and people around. For years, it has served as an artery of trade, carrying boats with farm produce to manufactured goods.

Apart from that, the Magdalena has a rich biodiversity: it has various species of fish, including catfish and other commercially important species. Its banks have rich growth in which birds, monkeys, and other wildlife make their homes. Wetlands and floodplains around it are part of the local ecosystems that function as nurseries for many species in the water and filtration systems in water purification.

The Magdalena River has grown very deep into the cultural and historical entwinements in the heart of Colombia. It has chronicled the fall and rise of civilizations from the indigenous cultures of the colonial era up to modern times. From its waters, exploration stories recount conquest and the development of the country.

2. What is the Flow Rate of the Magdalena River Like?

There is marked seasonality in the flow rate of the Magdalena River. It receives a fairly appreciable rise in flow during the rainy season, generally from April to November. Heavy rainfall in the Andean highland forces the water down the slope to the Magdalena River. This period of high flow is very important to maintain the volume of water in the river, replenish groundwater, and carry sediments downstream.

During the dry period, which starts in December and lasts until March, it decreases. Even during this time, it still keeps a base flow, which is very important for the aquatic life and functioning of the ecosystems depending upon it. The average recorded flow rate during the height of the rainy season can be several thousand cubic meters per second while in the dry season it can fall to a few hundred cubic meters per second.

The amount of water the Magdalena River carries affects not only the amount of transportation and trade that depends on it but also the method of farming on its sides. Its flooding during the high flow season deposits rich sediments in the area, further enriching the farms around it.

3. How to Measure Water Current of the Magdalena River?

Velocity Meter Method

This is a more traditional method based on the availability of mechanical or electronic velocity meters. These meters are located at some points within the river, measuring the water speed in those specific locations. This, of course, requires delicate positioning and multiple measures against different depths and across various parts of the river. Given the length and complexity of the Magdalena River, this method can be very time-consuming and may not lend a good representation of the overall water current without such effort.

Acoustic Doppler Velocity Profiler (ADCP) Method

An ADCP profiler is an advanced and efficient option. It detects the flow by sending out sound waves into the water and measuring the particle motion of water from the Doppler shift of the returning signal. It can measure the multidepth simultaneous water velocity with a very detailed profile of the water current. The ADCP meter could be mounted on boats for mobile measurements; they could also be installed on bridges and buoys for the purpose of continuous monitoring.

Buoy Method

The buoy method involves placing buoys carrying sensors in the river. These buoys measure the shifting water around them at the surface of the water. It may give a rough estimation of surface current, though it may not actually represent the current throughout the depth of the water column. This is one of the simpler methods of measuring discharge, and due to the many disadvantages, it cannot give a complete representation of the water current of the Magdalena River.

Of these, the ADCP flow meter proves to be more sophisticated and practical in measuring the water current of the Magdalena River.

4. How Do Doppler Principle ADCPs Work?

Principle of Operation: ADCP current profiler basically work on the principle of the Doppler effect. When an ADCP sends an acoustic signal into the water, its sound waves interact with the moving water particles. When the water particles are moving towards the ADCP, the reflected sound wave frequency becomes higher than the frequency of emission on account of the Doppler effect. In the case of water particles moving away from the ADCP, the reflected frequency becomes lower.

By precisely measuring this change in frequency, the ADCP current meter can work out the velocity of the water particles at different depths. It then takes these individual measurements of velocity and combines them to provide a complete profile of the current in the water. In this way, a full view of the flow of water is obtained, not only on the surface but right through the vertical section of the river.

5. What's Needed for High - Quality Measurement of the Magdalena River Currents?

Certain features are required, which would allow the equipment to make high-quality measurements of the currents of the Magdalena River.

The first and foremost is reliability in the materials used. It should be strong enough to withstand the surrounding environment this river has, being literally submerged in water, sediments, and temperature fluctuations all the time. Sometimes in the Magdalena River, there may be turbulent flows, and during a high-flow event, debris may flow that can hit the equipment.

Smaller in size, lightweight, and low power consumption are also desirable. A compact and light instrument is easier to handle and deploy on both a boat and attached to a buoy. Low power consumption would imply longer -term operation without frequent battery replacement or an ininterrupted power source.

Another important factor is cost-effectiveness. Lower cost allows a higher number of measurement equipment to be deployed, thereby allowing more points along the river.

Titanium alloy can be an excellent material for casing the ADCP itself. For a river like the Magdalena, the most valued properties of titanium alloy are those related to corrosion resistance. In addition, it is strong enough and durable to bear any physical impacts and pressure changes when deploying and operating the acoustic doppler velocity meter . Its relatively low density makes the equipment lightweight.

6. How to Choose the Right Equipment for Current Measurement?

Depending on the Purpose of Use

If the aim is to measure the horizontal cross-section of the river current, then one would apply a horizontal ADCP. HADCPs have been designed to precisely measure water flow in the horizontal plane for the purpose of understanding the overall movement of water across any particular section of the river.

If the interest for measurement involves the vertical cross-section of the river current, then a vertical type of ADCP should be selected. Since the vertical ADCPs will be able to record the velocity of the water at individual depths with high accuracy, therefore a detailed profile of how the water in the river is flowing vertically may be obtained.

Based on Frequency

Frequency depends essentially on the depth of the water in the Magdalena River. Normally, one would go for a 600 kHz ADCP for up to 70 meters of water depth. It will provide good resolution and accuracy at 600 kHz to measure the water current for relatively shallow water.

For deeper waters, say exceeding 70 meters up to about 110 meters, a 300 kHz ADCP will be more appropriate. At 300 kHz, the lower frequency can go deeper into the water and still measure the water current with reliability.

There are renowned brands of ADCPs from Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective option with excellent quality, the China Sonar ​PandaADCP is worth considering. It is made of all - titanium alloy material, ensuring durability and reliability. With its remarkable cost - performance ratio, it provides a great alternative for measuring the water current of the Magdalena River. 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.