How to measure the Coastal Currents of Wando?

1. Where is Wando?

Wando is a county located in the southwestern coastal part of South Korea. This place is so abundant in natural beauty and maritime resources. Wando consists of one major island and several small islands, forming a very complex and diverse coastline.

The seas and peculiar terrains of the islands dominate the landscape of the area. The coastline has a perfect mix of sandy beaches, rocky shores, and hidden coves. The islands have very good vegetation and wildlife on them. The people belonging to this place are quite closely associated with fishing and aquaculture. Wando has been famous for its quality seafood, abalone, seaweed, and various kinds of fish species. The South Sea near Wando is a warm-water body with a variety of marine life.

Fish resources around Wando Island include mackerel, flounder, and tuna. There is heavy growth of seaweed in the sea around Wando, which, besides being an important resource, serves as a part of the marine food chain. The sea has a great effect on the local climate, regulating the temperature and bringing sea breezes. The islands and waters are also popular with tourists, offering boating, fishing, and exploring the unique coastlines.

2. What is the situation of the coastal currents near Wando?

Various factors affect the coastal currents near Wando. Gravitationally, the major ocean current in the area is the Tsushima Current-a warm-water current that generally flows northward through the Korea Strait. This brings in warm and nutrient-rich water that greatly affects the local marine ecosystem and the coastal currents.

Tidal currents are also a powerful influence. The tidal range of Wando is relatively high, which causes very complicated current patterns due to the continuous tide rise and fall. Mainly, it depends on the shape of the coastline and underwater topography. The islands, channels among them, and shallow shoals underneath may bend and speed up the currents. For instance, the water would flow faster through narrow channels between islands or be deflected by a submerged shoal. Besides, the wind conditions, especially the seasonal winds, are able to drive the surface currents and affect the mixing of different layers.

3. How to observe the coastal water flow of Wando?

Surface Drifting Buoy Method: A surface - drifting buoy can be released into the water to observe the surface current. The buoy's movement is followed through time using a GPS or other tracking system. However, this method does have its drawbacks. First of all, it gives information on the surface current only and can be subject to wind and wave effects. For instance, if a strong wind happened to blow the buoy in another direction from the actual current, then it can lead to a fallacious measurement of the direction and speed of the current.

Anchor-Boat Method: An anchored boat is used to measure the current. The instruments used for measurement are lowered into the water from the boat, which measure the current at different depths. Although this allows for more detailed depth-wise measurements, there are also some disadvantages to it. The fixed position of the boat limits the area in which measurement can be taken and it may not capture the full variability of the currents in a large coastal area.

ADCP Method: The ADCP profiler method is more advanced and efficient in measuring the coastal currents. ADCPs emit acoustic signals into the water and measure the Doppler shift of the reflected signals to calculate the velocity of water at different depths. This gives a more comprehensive profile of the current from the surface to the seabed. ADCPs are less affected by surface disturbances and can operate continuously for long periods, giving a more accurate picture of the current structure.

4. How do ADCPs using the Doppler principle work?

These instruments are based on the principle of the Doppler effect. ADCPs emit high-frequency acoustic pulses into the water. These pulses, interacting with the moving water particles, undergo a frequency shift. If the particles are moving towards the instrument, the frequency of the reflected signal is higher than the emitted one; it is lower if they move in the opposite direction.

The ADCP meter has several transducers that send and receive signals at different angles. Through the analysis of Doppler shifts from different directions and at different depths, the device is able to calculate the three-dimensional velocity of the water. This means it can determine the horizontal and vertical components of the velocity, providing a detailed understanding of the current's structure and behavior.

5. What is required for high-quality measurement of the Wando coastal currents?

The equipment to be chosen for high-quality measurement over the coastal currents near Wando is required to be made up of reliable materials. These would be resistant to possible corrosion due to the salt water, potential exposure to storms, and the tides prevalent there. The size of such equipment should be small and easily deployable, recovered easily, particularly considering a complex coastal landscape with lots of islands and coves around.

A lightweight design is favored, as this makes the equipment easier to handle in the case of installation and maintenance. Low power consumption is necessary for longand autonomous operation. Cost-effectiveness is also important to enable large-scale measurements.

The casing of ADCPs should be made from titanium alloy. The metal has excellent resistance to corrosion, which is necessary given the corrosive nature of seawater. It is also tough and resilient and able to bear the water pressure that comes with fluctuations in depth. Its light weight allows for more comfort with diverse deployment methods.

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

The equipment to be selected for current measurement near Wando should be decided by considering the purpose of use, if the measurement is to be used for the vessel's navigation or for short-term research, a ship-mounted ADCP flow meter would be suitable because it provides real-time current information during the voyage.

For measurements near the seabed, such as in studies of sediment transport or benthic ecology, a bottom-mounted ADCP is preferred. It can capture the details of the near-bottom current. If long-term and wide-area monitoring of the coastal current is required, a buoy-type ADCP current profiler is ideal.

Regarding the frequency of ADCPs, for water depths up to 70m, a 600kHz ADCP is recommended. For depths up to 110m, a 300kHz ADCP is more suitable. And for deeper waters that might be found near Wando, such as areas with a depth over 1000m, a 75kHz ADCP is recommended.

There are well - known ADCP current meter 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 and offers an excellent cost - performance ratio. You can find more information on their website: https://china-sonar.com/.

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