How to measure the coastal currents of Panadura?

1. Where is Panadura?

Panadura is a coastal town in the Western Province of Sri Lanka. It is situated along the fine coastline of the Indian Ocean, not very far from the capital city, Colombo.

The town is famous for its beautiful beaches that run along with the blue waters of the ocean. The coastal area of Panadura is a tranquil place where the rhythmic lapping of waves against the shore soothes as a symphony. The local community here is vibrant because of the amalgamation of cultures and traditions. Fishing is an integral part of the local economy and way of life. Daily, fishermen take out into the sea their small vessels and set off on top of gentle swells, adding colors and vibrancy to this beachside view.

Adjacent to Panadura, the ocean waters form part of the extensive expanse of the Indian Ocean. The bay near Panadura offers a fairly enclosed area, which is quite good for several activities related to the sea, like small-scale fishing and boating for fun. In the coastal seabed topography, there are shallow sandy areas close to the coast and deeper levels further away, which affects water movements and the distribution of marine life.

2. What is the condition of the coastal currents near Panadura?

A combination of factors influences the coastal currents in the vicinity of Panadura. The monsoon winds have a strong influence. The southwest monsoon brings in powerful winds that can drive the surface currents in a particular direction. These winds push the water, creating a pattern of flow that can vary in strength and direction depending on the season and the intensity of the winds.

Moreover, large-scale ocean circulation contributes one after another. The general ocean current in the Indian Ocean with the equatorial currents as well as the influence exerted through the gyres can vary in this water movement. One more significant factor is the tidal forces. The regular tides create ebbs and flow and consequently a current, known as a tidal current, which can also interact with other currents driven by the ocean. That may be due to the fact that some coastlines and bathymetries around Panadura speed up or slow down these currents. For instance, underwater ridges or channels make the currents channelize or funnel, thus changing both its speed and direction.

3. How to Observe Coastal Water Flow of Panadura?

Surface Drift Buoy Method: One basic yet efficient way to carry on observation of the surface water flow is through surface drift buoys. These buoys are released into the water and carried along by the surface currents. By following the position of the buoys over time through GPS or other location-tracking systems, the direction and speed of the surface currents can be calculated. However, this can give information about only the very top layer of the water and might not be complete for different depths.

Anchor Boat Method: It involves the use of an anchor boat for deploying current-measuring instruments. The boat is anchored in a given location, and the current meters are submerged into the water at different depths. In this way, it becomes possible to measure the speed and direction of flow of current at different vertical levels. However, this method has a partial area of coverage and is more or less stationary.

ADCP Method: Basically, ADCP is a higher order and efficient method of measurement for coastal currents. It basically applies the Doppler effect in measuring the velocity of the water at different depths. The principle of ADCP works by emitting an acoustic signal, and the Doppler shift of the reflected signals from the particles in the water gives it a detailed profile from the surface to a certain depth. This gives a better understanding of the vertical structure of the coastal currents near Panadura and is preferred by many oceanographers.

4. How do ADCPs using the Doppler principle work?

In principle, ADCPs work according to the Doppler principle. They emit high-frequency acoustic pulses into the water column. These pulses interact with suspended particles in the water. Since the water is in motion, so do the particles, and if acoustic pulses are reflected back from these particles to the ADCP profiler, a shift occurs in the frequency of the received signal compared to the emitted signal. This frequency shift, commonly known as the Doppler shift, is directly related to the velocity of the water flow.

The ADCP meter is fitted with several transducers, which are able to transmit and receive signals in various directions. Measuring the Doppler shift of the signals received at distinct angles and depths from each other with high accuracy makes it possible to calculate the speed and direction of water currents in every point of the water column. It allows the current field to be mapped three-dimensionally and provides valuable data on the horizontal and vertical components of coastal currents.

5. What are the requirements for accurate measurement of the Panadura coastal current?

The equipment to be used for high-quality measurement of the coastal currents in Panadura should possess certain characteristics. First, the material of the equipment should be reliable to stand the corrosive effects of seawater and harsh marine conditions. Small size and lightweight are an added advantage because it enhances the ease of handling and deployment either on a boat, buoy, or other platforms.

Low power consumption for long-term measurements is essential; therefore, the equipment has to work continuously without replacing the batteries frequently or requiring too large a power supply. Regarding cost-effectiveness, such equipment should be reasonably priced for people to afford and permit them to deploy multiple units for more extensive coverage of monitoring.

For ADCPs, a casing of the highest class may be made of a titanium alloy. In sea water, the resistance to corrosion will be very high for the purpose of long-term durability of the equipment. This will entail a high strength-to-weight ratio, thus offering structural integrity while still maintaining a low weight. Also, titanium alloy is resistant to high pressures, hence it can be used in various water depth scenarios of the Panadura coastal area.

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

To select the proper equipment for current measurement in Panadura's coastal waters, several factors should be considered.

Depending on the purpose of use, there are various types of ADCPs. An ADCP flow meter installed on a moving vessel is suited for measurements. A shipborne ADCP will be able to measure the currents while the ship is moving along the coast in a continuous stream. If the intention is to monitor the currents at a fixed point near the seabed, a sit - bottom ADCP is a good option. It can be moored on the ocean floor and it records the water flow as it passes over the monitor. For applications where a floating platform is more convenient, there comes a buoy-mounted ADCP.

In the case of the ADCP current profiler frequency, it varies with water depth. For depths up to 70m, an ADCP of frequency 600kHz is advisable due to its high-resolution measurements. For depths up to 110m, a 300kHz ADCP is more suitable. For even deeper waters of up to 1000m, a 75kHz ADCP is more suitable to ensure accurate and reliable current measurements.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option, the China Sonar PandaADCP is a great alternative. It is made of titanium alloy and offers an incredible 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.