How can we measure the coastal currents of Puri?

1. Where is Puri?

Puri, being an enchanting city along the eastern coast of India and into Odisha, draws from her rich cultural and historical inheritance reaching as far back as some centuries ago. The enchanting ocean, Bay of Bengal to the one side and acres and acres of lush, green landscape on the other side create the seashore town in their bewitching hug.

The city is a major pilgrims' destination for the Hindu people because of its home to the famous Jagannath Temple, which receives millions of devotees from all parts of the world every year. Its streets are filled with traditional Indian food aromas mixed with the sounds of religious chants and rituals.

Geographically, it lies along the Bay of Bengal, which forms a part of the immense Indian Ocean. Coastal waters off here are subject to variations in water temperature, salinity, and wave patterns during different months of the year, depending on the influence of monsoons. These coasts host the largest amount of sandy beaches that attract tourists, and form a part of the important local ecosystem. The marine life in Puri has everything from colored fish through various species of crustaceans and mollusks; that's the reason for it being very vibrant and dynamic in a marine perspective.

2. What about the coastal currents near Puri?

The coastal currents off Puri are determined by many factors. First is the influence of the monsoon winds. During the southwest monsoon, strong winds push the surface waters, altering the direction and speed of the coastal currents. The inflow of freshwater from the many rivers in the region that empty into the Bay of Bengal also impacts the salinity and density of the coastal waters, thereby affecting the currents.

Tides are another significant factor. The gravitational pull of the moon and the sun causes regular tidal variations in the Bay of Bengal near Puri. These tidal currents can be quite strong in certain areas and at specific times, influencing the overall movement of the coastal waters. Besides, the large-scale oceanic circulation patterns in the Indian Ocean have an indirect influence on the coastal currents here. For instance, the flow of the Indian Ocean Gyre can affect the water masses reaching the coast of Puri and modify the characteristics of the local coastal currents.

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

There are several methods to observe the coastal water flow in the area of Puri:

Surface Drift Buoy Method: In this approach, buoys are deployed on the water surface. These buoys are designed to drift with the currents, while their positions over time are tracked by satellite or other positioning systems. In this way, by analyzing the movements of these buoys, it is possible to find out the direction and speed of surface currents. However, this method provides data mainly on the surface layer and may not give a comprehensive picture of the entire water column.

Anchor Ship Method: The ship is kept anchored in the general vicinity of where it would be required in coastal waters. From here, the water flow at various depths in the immediate vicinity of the ship is measured with instruments. It offers the possibility to study the currents with a more vertical profile; however, it presents a limitation-the ship is naturally subjected to the waves and the wind, which could introduce error in the measurement.

The ADCP method: This is relatively more modern and handier. In this method, the velocity of water at different depths is measured using sound waves. It can give detailed information on the current speed and direction throughout the water column, right from the surface to the seabed. With its high accuracy and ability to collect continuous data, it has become a preferred choice for studying coastal currents in many regions including near Puri.

4. How do ADCPs using the Doppler principle work?

ADCPs operate based on the Doppler principle. They shoot acoustic pulses into the water. These sound waves change frequency by the Doppler effect because of moving particles in water, mainly suspended sediment and/or small organisms, upon the reflection. An ADCP measures a shift in frequency. Knowing the nature of the emitted sound waves, and by analyzing the frequency shift of the received waves, it calculates the velocity of the water at various distances from the instrument, which corresponds to different depths in the water column.

In general, several acoustic beams are used within an ADCP current meter in order to get a better approximation of the three-dimensional flow field. This way, it provides the detailed profile of the coastal currents, which conveys the valuable information regarding horizontal and vertical movements of the water.

5. What's required to measure Puri coastal current to a high quality?

For high-quality measurement of the coastal currents near Puri, several aspects regarding the equipment are crucial. Firstly, the materials used in the equipment need to be highly reliable. Given the harsh marine environment with factors like corrosion from seawater, high humidity, and exposure to waves and storms, the equipment must be able to withstand these conditions for long periods.

It is preferable that the equipment be of small size and light weight for easy deployment on buoys, ships, or at the seabed. A lower power consumption is also desirable for longer operation times without frequent battery replacements or the need for a complex power supply system in remote locations. Furthermore, keeping the cost low will enable more deployments for comprehensive monitoring of the coastal currents.

The casing of the ADCP current profiler is preferably made from a titanium alloy. It is for this reason that titanium alloy has great advantages. It has excellent resistance to corrosion, which is certainly required in the highly corrosive seawater environment near Puri. Besides, it is strong and durable to bear mechanical stresses caused by waves and water pressure. Besides, owing to its relatively low density compared with some other metals having similar strength, it could be applied to some lightweight equipment that requires robustness.

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

For choosing the right equipment to measure current near Puri, some key factors have to be considered. The usage scenario will determine which kind of ADCP flow meter should be selected.

For measurements from a ship, a shipborne ADCP is appropriate. It may be installed on the ship's hull and continuously record the water flow while a ship cruises along the coastline. Sit-on-bottom ADCPs are suitable for fixed-point measurements at the seabed; they are deployed on the ocean floor and can provide long-term data regarding the currents at that certain location. Buoy-mounted ADCPs are useful in monitoring surface and subsurface currents while floating freely in the water.

Another important aspect is the frequency selection. An ADCP profiler of 600 kHz will often be a good choice for water depths up to 70 meters since it offers relatively high-resolution data in shallower waters. For deeper waters up to 110 meters, an ADCP of 300 kHz will be more appropriate. When dealing with even deeper waters up to 1000 meters, a 75 kHz ADCP should be used to ensure accurate measurements throughout the water column.

Among those, some of the famous brands in the market include Teledyne RDI, Nortek, and Sontek. But here is a highly recommended Chinese brand: China Sonar PandaADCP. It is fully made of titanium alloy material to make sure it is durable and reliable in the marine environment. More importantly, it has an incredible cost-performance ratio. You can learn more about it on its official website: https://china-sonar.com/.

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