How can we measure the coastal currents of Thuwal?

1. Where is Thuwal?

Thuwal is a coastal area in Saudi Arabia. It faces the Red Sea-a body of water highly recognized for its exceptional ecological and geographical features. The landscape setting of Thuwal combines arid desert that extends inland with a beautiful coastline and sandy beaches.

It has a budding community that is increasingly fascinated by marine-related activities. The Red Sea off Thuwal hosts copious amounts of marine life. The clear and warm waters harbor a variety of coral reefs, which are considered some of the most spectacular reefs in the world. These are home to myriad numbers of fish species, from the colorful reef fishes down to the larger pelagic species that pass through.

These bays and inlets constitute important aspects of the marine environment around Thuwal, where the sheltered water is utilized for several uses such as small-scale fishing, leisure boating, and acts as a natural nursery for many marine organisms. Equally, Thuwal occupies a privileged geographic position in regard to climatic influences due to the Red Sea; this implies a general relatively mild temperature compared with most of the interior areas.

2. What is the condition of the coastal currents around Thuwal?

Various driving factors are responsible for the coastal currents around Thuwal. Among these, tidal currents provide a very strong force. The tides in the Red Sea are driven by the gravitational pull of the moon and the sun. Depending on the lunar cycle and local topography, the tidal range and the currents associated with it change. During high tide, the water covers the bays and the inlets, while on low tide, it recedes. In places, these tidal currents may be quite strong and thus substantially account for the apparent movements of water near the coast.

The action of the wind is also a very vital factor in the creation of currents. The prevalent winds blow the surface water and create currents in certain directions. The change in the wind patterns during different seasons might also result in the changes in the direction and strength of the currents. For instance, during the winter months, the winds might blow from a different direction than in the summer months, causing the surface currents to change accordingly.

The shape of the seabed topography and coastline is an important determinant for the current patterns. The underwater contours may provide channels or barriers for the water. Headlands and bays can accelerate or decelerate the currents as the water moves around them. In addition, differences in water temperature and salinity may contribute to the formation and movement of coastal currents. Warmer surface water can interact with cooler, deeper water, leading to density - driven currents.

3. How to Observe the Coastal Water Flow of Thuwal?

There are several ways to observe the coastal water flow around Thuwal.

Surface Drifting Buoy Method: Buoys are set into the water and fitted with tracking devices such as GPS. Due to the fact that these buoys move with the set of surface currents, one is then able to know their movement over time. It is by analyzing the course and speed of the buoy that the direction and speed of the surface currents can be determined. This method constitutes a simple and inexpensive method for gaining insight into surface current patterns.

Moored - Ship Method: A ship is moored in some position in the waters offshore. Current-measuring instruments are deployed from the ship to measure the speed and direction of the water at various depths. This method suffers from some disadvantages. The presence of the ship can affect the local current patterns, while its stationary position restricts the area of measurement to the vicinity of the ship.

Acoustic Doppler Current Profiler (ADCP) Method: The ADCPs are the advanced and more efficient means of measuring coastal currents. They can be mounted on various platforms, like boats, buoys, or even on the seabed. The ADCPs send acoustic pulses into the water and measure the Doppler shift of the reflected signals. From these Doppler shifts, they can work out the velocity and direction of the water current at several points from the surface to a particular depth; hence, a better realization of current structure is achieved.

4. How does the use of the Doppler principle apply to ADCPs?

ADCPs operate according to the Doppler principle. Acoustic pulses are transmitted into the water. As these pulses encounter particles or other objects in the water that are moving with the current, the frequency of the reflected signal changes. This change in frequency-the Doppler shift-is directly related to the velocity of the moving objects and, by extension, the velocity of the water current.

The ADCP measures the Doppler shift of the reflected acoustic signals from multiple directions and at different depths, and analyzes these Doppler shifts to calculate the speed and direction of the water current at each measurement point. The device is usually equipped with several transducers that emit and receive acoustic signals, by which it is able to generate a three-dimensional profile of the current.

5. What's needed for high - quality measurement of Thuwal coastal currents?

The equipment to carry out high - quality measurements of the coastal currents near Thuwal should possess certain characteristics.

Reliable materials provide housing for the measuring device which should be resistant both to corrosive action of saltdome water and various water pressures. In this relation, making the housing from materials, like a titanium alloy, is advantageous because the materials offer excellent resistance against corrosion, withstand water pressure.

• Small Size and Light Weight: The small size and lightweight device is advantageous in that it allows for easier installation and deployment on various platforms, such as buoys or small boats. It also simplifies transportation and handling.
• Low Power Consumption: For long-term measurements, low power consumption is needed. This ensures that the power sources, such as batteries, could last for a longer period without more frequent recharging or replacement of the batteries.
• Cost-Effectiveness: Large-scale measurement calls for an economic approach. The measuring devices should be cost-effective in order to allow monitoring of the coastal currents extensively and continuously.

6. How to Choose appropriate equipment for current measurement?

While selecting the right equipment for current measurement around Thuwal, the following could be considered:

Based on Use

Ship - Mounted ADCP: When the measurement is to be done from a ship, then a ship-mounted ADCP will be quite suitable. It gives current information in real time as the ship moves through the water. 

Bottom - Mounted ADCP: A bottom-mounted ADCP is used for the measurement of the current near the seabed. These measurements are about the currents close to the bottom, quite necessary in understanding the bottom interface to the water column.

Buoy - Mounted ADCP: This is an easy alternative to making long-term and wide-area measurements. A buoy mounted ADCP can stay in place for a long time, monitoring continuously the coastal currents over a large area.

Based on Water Depth

• Up to 70m of water depth, 600kHz is often an appropriate value for the ADCP.
• Up to 110m, a 300kHz ADCP is better.
• For very deep waters reaching up to 1000 meters, a 75kHz. ADCP is more fit.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar ​PandaADCP, is also worth considering. It is made of all - titanium alloy material, providing excellent durability and performance. Moreover, it offers an incredible cost - performance ratio. You can find more information about this brand on their website: ​https://china-sonar.com/.

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