How do we identify the coastal currents of Prachuap Khiri Khan?

1. Where is Prachuap Khiri Khan?

Prachuap Khiri Khan is one of the provinces in Thailand and is located in the Gulf of Thailand. It is especially known for its beautiful girth of coastlines, boasting length upon length of sandy beaches against a backdrop of deep blue sea. The province houses quaint seaside towns and fishing villages.

Fisheries, tourism, and agriculture contribute to the local economy. The surrounding natural beauty attracts numerous tourists into this area, for instance, for sunbathing, swimming, and snorkeling. The local people are closely affiliated with the sea, and the fishing industry is very crucial in their way of life.

The nearby body of water, the Gulf of Thailand, is warm and quite shallow. Abundant in fish, shellfish, and even coral reefs, it greatly affects the local climate and weather pattern outside of the sea area itself.

2. What is the situation of the coastal currents near Prachuap Khiri Khan?

The complexity of the coastal currents near Prachuap Khiri Khan is under the influence of several factors. The most important influence is that of tidal currents. Tides in the Gulf of Thailand are semi-diurnal; induced by gravitational forces of both moon and sun, each day there is roughly a couple of high tides and low tides. Tidal currents may develop considerable strength, in particular nearshore and around constrictive waterways, such as mouths of rivers or inlets. These currents play a very important role in the transportation of sediments and nutrients, which are vital for the health of the coastal ecosystem and the productivity of fishing grounds.

Monsoons also have a great influence. The southwest monsoon, running from May to September, carries strong winds that can drive the surface currents in a certain direction. The northeast monsoon, between November and February, alters the wind direction and hence the direction and speed of the coastal currents. Their mutual interaction between tidal and monsoon-driven currents develops a quite complex and dynamic flow pattern.

The local bathymetry, such as the shape of the seabed and any underwater features, including ridges and channels, may act to deflect and alter the coastal currents. Discharges from rivers and canals into the sea also have an impact on the current patterns. This freshwater input is due to density differences and can give rise to quite complex current systems.

3. How to Observe Coastal Water Flow of Prachuap Khiri Khan?

There are many methods for observing the coastal water flow in Prachuap Khiri Khan.

The Surface Drifting Buoy Method

This is quite a straightforward and practical method. The buoys are set free in the water and fitted with GPS or any other types of monitoring. Due to the buoys being at the mercy of the currents, their positions and movements over time will be able to determine which direction and speed the surface currents are moving. The buoys must be specifically designed to resist the local marine conditions with regard to waves and salinity.

The Anchored Ship Method

A ship anchors at a location and current-measuring instruments are lowered from the ship. These instruments are capable of measuring water flow velocity and direction at different depths of water. This method has its drawbacks. The ship itself may be subjected to the action of waves and winds, which may result in incorrect recordings. It is not very efficient in order to scan a vast area.

ADCP Method

This is one of the advanced and effective methods of measurement of the flow in coastal water. ADCPs are capable of measuring the velocity profile of water currents through a wide range of water depths. Basically, they work by sending out sound waves into the water and measuring the Doppler shift of the reflected waves. It gives the detailed structure of the current from the surface to the seabed.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of Doppler. They send out acoustic pulses, which is actually a form of sound waves, into the water. These sound waves scatter against particles in the water, such as sediment, plankton, and other small particles in the water. When the sound waves reflect off these particles back to the ADCP current profiler, the frequency of the reflected waves changes due to the Doppler effect.

If the particles are moving towards the ADCP, then the frequency of the reflected wave is higher than the original emitted frequency. In contrast, if the particles are moving away from the ADCP flow meter, the frequency of the reflected wave would be lower. By measuring this frequency shift accurately, the ADCP meter is able to compute the velocity of the particles. Since the particles are moving with the water current, the velocity calculated in the case of the particles is the measure of water current velocity.

Some ADCPs also can emit sound pulses in more than one direction, thus enabling current velocity measurements three-dimensionally and at depth. For instance, vertical profiles could, depending on certain conditions, measure from the surface down to the seabed in discrete intervals to yield a comprehensive picture of the current structure.

5. What is required to carry out high-quality measurement of Prachuap Khiri Khan Coastal Currents?

The equipment should be made of reliable materials for high-quality measurement of the coastal currents in Prachuap Khiri Khan. Since the marine environment is very harsh, with saltwater corrosion and possible physical impacts from waves or debris, a casing that would be durable enough is required.

The size of the equipment should be small enough to be easily deployed, in particular, when operating it from small boats or in shallow coastal waters. A lightweight design may also be favorable since then handling and installation will be easier to perform.

Long - term measurements require low power consumption. Low cost of equipment will make it possible to use a large number of instruments for measurements. For ADCPs, the casing must preferably be of titanium alloy. This material possesses excellent corrosion resistance, which is so essential in the marine environment of Prachuap Khiri Khan. It will withstand the corrosive effects of saltwater over a long period. This material is also strong and with a high strength-to-weight ratio, thus offering a durable yet lightweight structure that provides effective protection for the internal components in an ADCP profiler.

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

When selecting appropriate equipment in Prachuap Khiri Khan to measure currents, the first criterion to use would be the intended usage.

For Measurements from a Moving Vessel

A ship - borne ADCP meter would be appropriate. It can deliver current data in real time as the ship is moving, thereby enabling an understanding of the flow of water at different locations.

For Measurements at a Fixed Location near the Seabed

A bottom - mounted ADCP flow meter would serve well. It can monitor the current continuously at that one point, hence yielding consistent data over time.

For Measurements that Need to Cover a Wide Area and are not Restricted to a Specific Depth A buoy - type ADCP current profiler is appropriate. It can cover a larger area and is not limited to a particular depth.

Frequency choice: with respect to the choice of frequency, a 600kHz ADCP should suffice for water depths up to 70m. Between 70 and 110m, one may need a 300kHz ADCP. A 75kHz ADCP for very deep waters up to 1000m is suggested.

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 a great cost - performance ratio. You can find more information about it on the website: https://china-sonar.com/.

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