How to Measure the Water Current of the Arab River

1. Where is the Arab River?

The Arab River is a major river in the Middle East. It forms part of the boundary between Iraq and Iran. Many small tributaries feed the river, and its waters flow into the Persian Gulf.

The surroundings of the Arab River hold tremendous strategic and economic significance. There are ports and heavy industries like oil refineries alongside its banks. The local ecologies are also affected by the river. There are marshes and wetlands nearby, hosting a wide range of flora and fauna comprising waterfowl, fish, and types of reeds and grasses.

2. What is the flow rate of the Arab River like?

The flow rate of the Arab River is influenced by several factors. First, it depends on the rainfall in its upstream catchment area, which is normally low in the arid and semi-arid climate of the region. Besides, water utilization and management policies of the two countries-Iraq and Iran-through which it flows, are also a factor.

This flow rate increases in case of increased rainfall in the catchment area, while it significantly decreases due to extensive water drawing for agricultural and industrial use. The topography of the river basin, determining the method of collection and drainage of the water, is another controlling factor of the average flow rate.

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

Velocity Meter Method

Traditional approach: In this approach, mechanical or electronic velocity meters could be placed at specific points in the water to measure the speed of the water passing by. However, for a comprehensive coverage of the current, these meters need to be deployed at several locations and depths. This could be rather time-consuming and may not give a continuous profile of the current at all levels of the water column.

Acoustic Doppler Current Profiler Method

The ADCP current meter method is more sophisticated. It uses sound waves to measure the water velocity at several depths simultaneously. It can give a detailed profile of the current from the surface to the riverbed by emitting acoustic signals and analyzing the Doppler shift of the reflected signals. The result is a more valid and comprehensive measurement of water current across different sections of the river.

Buoy Method

This is done by installing buoys in the river and then monitoring their movements for some time. The buoys, by reason of water current, get displaced, indicating the speed and direction of flow.

But this method has limitations. It may not provide accurate velocity measurements at different depths and can be affected by external factors such as wind and waves, which can influence the movement of the buoys.

Among these methods, the ADCP flow meter method is the more advanced and convenient option for measuring the water current of the Arab River.

4. How do ADCPs using the Doppler principle work?

ADCPs are based on the principle of the Doppler effect. When an acoustic signal is transmitted from the ADCP current meter transducer into the water, the sound waves are scattered by the moving water particles. Since the water is in motion, the frequency of the reflected sound waves back to the transducer shifts, a process known as the Doppler shift.

If the water is moving toward the transducer, the frequency of the reflected waves will be higher than the emitted frequency; if the water is moving away from the transducer, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP profiler can calculate the velocity of the water in various directions and at different levels within the water column. With that, it can set up a good record of water current, yielding very necessary information on speed and the direction of the flow right from the surface to the riverbed.

5. What's required in terms of high - quality measurement in Arab river currents?

There are certain features that, if available on the measurement equipment, high-quality measuring of the currents of Arab rivers will be achieved with.

Materials of its construction should be reliable due to the requirements for exactitude and precision in measurements, which it would finally deliver. Small size is advantageous, as it offers greater feasibility in deployment and retrieval from the river at locations difficult to access. The equipment has to be lightweight so it is easy to install, using less effort while handling it.

Low power consumption is necessary to operate the equipment for long periods without frequent battery replacement or a complex power supply setup.

Cost-effectiveness is another important factor, as it allows wider usage and larger-scale measurement campaigns.

In the case of an ADCP flow meter casing, titanium alloy is one of the best materials. Titanium alloy has many advantages. It is highly resistant to corrosion, which is very important because the equipment continuously comes into contact with water that may contain several minerals, sediments, and other pollutants. It also has a good strength-to-weight ratio that makes it strong enough to constitute a durable yet lightweight casing. In addition, it could withstand the mechanical stresses due to deployment and operation under flowing water in the Arab River.

6. How to choose the right equipment for current measurement?

When choosing the proper equipment for measuring the Arab River's current, two main elements should be taken into account.

Firstly, this depends on the usage purpose and, for horizontal cross-measurement, the Horizontal ADCP is suitable. It is designed to measure the flow velocities across a horizontal plane in the river with high accuracy for the purpose of understanding the lateral distribution of the current. In the case of vertical cross-section measurement, the Vertical ADCP would be more appropriate because it focuses on profiling the current from the surface to the bottom along a vertical line in the water column.

Different frequencies of ADCPs are suitable for different water depths. For instance, the ADCP profiler with a frequency of 600 kHz is suitable for the water depth within 70 m. It can provide an accurate current measurement in relatively shallow parts of the Arab River. An ADCP flow meter operating at 300 kHz can be more appropriate for deeper waters up to 110 m that may be useful in sections where the river has a greater depth.

There are well-known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost-effective option with good quality, the China Sonar PandaADCP is highly recommended. It is made of all-titanium alloy material and offers an incredible price-performance ratio. You can find out more about it on its website: https://china-sonar.com/.

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