How to measure the coastal currents of Pottuvil?

1. Where is Pottuvil?

Pottuvil is a beautiful coastal town in the Ampara District of Sri Lanka. It is situated on the southeastern coast of the island, bordering the enormous expanse of the Indian Ocean.

The town has a unique geographical setting. Its coastline is characterized by long stretches of sandy beaches that are kissed by the warm waters of the ocean. The area around Pottuvil is rich in natural beauty, with palm-fringed shores and a landscape that is a harmonious blend of land and sea. The local community here has a strong connection to the ocean, with fishing being a primary livelihood for many. The fishermen's boats can often be seen lined up along the shore, their colorful hulls adding a splash of vibrancy to the coastal scenery.

Adjacent to Pottuvil, the ocean waters are part of a dynamic marine environment. The bay near the town provides a sheltered space for small - scale fishing activities and also serves as a haven for various marine species. The seabed topography in the coastal regions varies, with shallow levels near the beach and deeper troughs farther out. This particular variation in depth is very instrumental in influencing the behavior of the current at the coast and therefore the distribution of nutrients, with consequences for the marine ecosystem.

The town also boasts of a special cultural heritage. The local customs and festivals also relate to the ocean and fishing. People in Pottuvil respect the sea so much as it is the provider of food for them and their livelihood.

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

The coastal currents off Pottuvil are influenced by a number of factors. The monsoon winds are a significant factor. The northeast monsoon, which generally occurs from December to February, brings in winds that can drive the surface currents in a particular direction. These winds can cause the water to move along the coast, affecting the circulation patterns.

The broader oceanic circulation patterns of the Indian Ocean also have an impact. Currents such as the South Equatorial Current and the influence of the Indian Ocean Gyre play a part in determining the general direction and strength of the water movement in the area. Tidal forces are another important factor. The tides in the region cause the water to rise and fall, creating tidal currents that interact with the other ocean - driven currents. The shape of the coastline and bathymetry of the seabed around Pottuvil would either facilitate or inhibit the currents. For instance, headlands and bays will give a shift in the directions of flow and speed since water will be deflected or funneled.

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

Surface Drift Buoy Method: One of the practical ways for observation of the surface water flow is by using Surface drift buoys. These are designed to float on the water's surface and are carried along by the currents. By monitoring the positions of the buoys over time, the direction and speed of the surface currents can be estimated using tracking systems such as GPS. However, the majority of this method is intended for the surface layer; therefore, it may not provide complete information about the currents at different depths.

Anchor Boat Method: In this method, an anchor boat can be used to measure the flow of water. The boat is anchored at a location, and current-measuring instruments are deployed at different depths from the boat. This allows for the determination of the speed and direction of the current at different vertical levels. However, this method has limitations in that it is relatively stationary and may not cover a wide area efficiently.

ADCP method: The ADCP profiler method is more advanced and efficient to measure coastal currents. The method works on the principle of the Doppler effect. ADCP can measure the velocity of water at different depths by sending acoustic signals into the water and analyzing the Doppler shift of the reflected signals from particles in the water. This gives a detailed profile of the current from the surface to a certain depth, hence giving a more comprehensive understanding of the vertical structure of the coastal currents near Pottuvil.

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

The ADCPs work on the principle of the Doppler. They emit high-frequency acoustic pulses into the water column. These pulses interact with the suspended particles in the water, like plankton or sediment. As the water moves, the particles also move with it. When the acoustic pulses are reflected back to the ADCP meter from these particles, there is a frequency shift in the received signal compared to the emitted signal. This frequency shift, known as the Doppler shift, is directly related to the velocity of the water flow.

The ADCP flow meter has several transducers that can send and receive signals in different directions. By precisely measuring the Doppler shift of the received signals from different angles and depths, it can calculate the speed and direction of the water currents at various points in the water column. This enables the creation of a three - dimensional view of the current field with much valuable information about both horizontal and vertical components of coastal currents.

5. What is needed for a high - quality measurement of Pottuvil coastal currents?

The equipment has to be of certain qualities to conduct high-quality measurements of the currents in Pottuvil. Equipment material should be reliable and durable enough to operate under such corrosive conditions as sea water and aggressive marine atmosphere. Compact size and weight are advantageous because these provide easy transportation, deployment, and handling on a boat, buoy, or any other platform.

The equipment must be of low power consumption for long-term measurements. It should operate without constant battery replacements or large-scale power supplies. Cost-effectiveness is also one of the important aspects. It has to be affordable to a large number of users, including farmers, for whom several units can be deployed to enable better monitoring.

In the case of ADCPs, the casing can be made of titanium alloy. Titanium alloy represents very good resistance to corrosion in seawater, which ensures the long-term integrity of the equipment. It has a high strength-to-weight ratio, which means structural stability with a minimum weight. Besides, titanium alloy withstands high pressures, making it suitable for different water depth scenarios in the Pottuvil coastal area.

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

Various factors are considered during the selection of appropriate equipment to measure current in Pottuvil's coastal waters.

Depending on the purpose of use, there exist several types of ADCPs, The ship-borne ADCP current profiler is one of them and can be used from a moving vessel. It can measure the currents while the vessel is sailing along the coast, providing a continuous stream of data. If the aim is to monitor the currents at a fixed location near the seabed, a sit - bottom ADCP is a good choice. It can be placed on the ocean floor and record the water flow passing over it. An ADCP on a buoy is a better option where a floating platform would be more convenient.

Frequency of ADCPs depends on the water depth. For the water depths up to 70m, an ADCP with 600kHz is recommended, as it provides high-resolution measurements. For depths up to 110m, a 300kHz ADCP would be more appropriate, while for deeper waters up to 1000m, a 75kHz ADCP would be better for accurate and reliable current measurement.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective alternative, the China Sonar PandaADCP is a great option. It is made of titanium alloy and offers an excellent cost - performance ratio. You can find more information about it on its website: https://china-sonar.com/.

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