How to Estimate the Coastal Currents of Anakapalle?

1. Location of Anakapalle

Anakapalle is a town situated in the Visakhapatnam district of Andhra Pradesh, India. It falls in a region that is a tapestry of vibrant landscapes and rich cultural heritage. The town is surrounded by verdant hills and agricultural fields, with the air often filled with the fragrance of local crops and the sounds of rural life.

Geographically, it enjoys proximity to the Bay of Bengal. The shoreline off Anakapalle is an interesting combination of sandy beaches and rocky outcrops. The sandy beaches lie along for miles, inviting locals and tourists alike to enjoy the sun and the sea. The rocky areas are home to a diverse range of marine life, from barnacles and mussels clinging to the rocks to small fish seeking shelter in the crevices. The surrounding waters are part of the vast Bay of Bengal, which is a dynamic and complex marine environment.

In the coastal waters of the area, monsoons play a major role in determining changes in water temperature, salinity, and wave energy throughout the year. The local fishing communities have an attachment with these waters from which they derive their livelihood and continue to practice traditional fishing techniques passed on through generations.

2. What is the state of the coastal currents off Anakapalle?

The coastal currents off Anakapalle are influenced by several features. The most important influence is that of the monsoon winds. Indeed, the southwest monsoon brings strong winds which, at times, may appreciably affect the surface currents. Such winds might push the water in a given direction and change the usual surface flow pattern. Another critical role is played by the fresh water input from the surrounding rivers and streams that are pouring into the Bay of Bengal. The addition of fresh water changes the salinity and density of the coastal waters; as a result, it will promote the generation of density-driven currents and thus alter the general circulation.

Tides also play a pivotal role. The Bay of Bengal off Anakapalle has semi-diurnal tides, with two high and two low tides in a day. The tidal currents during these periods are pretty strong and can mix the water masses. The gravitational pull of the moon and the sun is the main cause of these tides. Besides, the greater ocean-wide current patterns within the Indian Ocean have the potential to indirectly affect coastal currents. For instance, large-scale circulation patterns like the Indian Ocean Gyre would significantly influence water masses reaching the coasts of Anakapalle, in turn affecting the characteristics of coastal currents.

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

Surface Drift Buoy Method: In this technique, surface-floating buoys are deployed in the coastal waters. These buoys are designed in a way that they can drift with surface currents. Their locations in space are tracked over some period of time, usually through satellite-based tracking systems or other positioning techniques. By analyzing the motion of these buoys, we can obtain quite important information about the direction and speed of the surface currents. However, this approach mainly focuses on the surface layer and may not provide a comprehensive understanding of the entire water column's current situation.

Anchor Ship Method: This involves the anchoring of a ship at a particular point within the coastal area. In this method, instruments are installed around the ship to measure water flow at various depths, providing an opportunity for a better, almost precise examination of the vertical profile of the currents. However, this method has its disadvantage. The ship may be affected by waves and wind, which may introduce error into the measurements and further affect the accuracy of data being collected.

ADCP Method: The ADCP meter method is an advanced and efficient means of measurement of coastal currents. The principle of the method is based on measuring the velocity of water at different depths simultaneously by sound waves. It can give in detail the profile of the current speed and direction, extending from the surface to the bottom of the water. Due to its high accuracy and ability to collect continuous data, it has become one of the favored choices in studying coastal currents in many regions, including near Anakapalle.

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

In principle, ADCPs apply the Doppler principle in their operations. They send acoustic pulses into the water. The moment these sound waves come into contact with moving particles in the water, like suspended sediment or small organisms, the frequency of the reflected waves is altered by the Doppler effect. This frequency shift is measured by the ADCP. By knowing the properties of the emitted sound waves and analyzing the frequency shifts upon reception, it estimates the water velocity at distinct ranges from the instrument, which is, of course, corresponding to various depths within the water column. Normally an ADCP is set with several acoustic beams for fairly good representation of the three-dimensional flow field. This allows the ADCP flow meter to provide a full and detailed view of the coastal currents, both in horizontal and vertical water movement.

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

For high-quality measurement of the coastal currents near Anakapalle, several requirements are essential in regard to equipment. First of all, the materials of equipment should be reliable. Since it is a marine environment with such factors as seawater corrosion, high humidity, and exposure to waves and storms, the equipment must be able to survive them for long-and high-quality measurements.

A smaller size and weight of equipment are preferable; it's more convenient for deployment, whether on buoys, on ships, or at the seabed. It is desirable to have a low power consumption for the operation in longer terms without the need for frequent battery replacements or a complicated power supply system in remote locations. The other important factor is cost-effectiveness, since it can be deployed much more for comprehensive monitoring of the coastal currents.

The casing is preferably made of titanium alloy. Titanium alloy has great resistance to corrosion, important in the corrosive seawater around Anakapalle. It is also strong and durable to resist mechanical stresses resulting from waves and water pressure. Besides, its relatively low density compared to some of the metals of similar strength makes it suitable for equipment that needs to be light with robustness.

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

When choosing the right equipment for current measurement near Anakapalle, the usage purpose should be considered. For ship-based measurements, a ship-borne ADCP current profiler is a suitable option. It can be mounted on the ship's hull and measure the water flow as the ship moves along the coast. Sit-on-bottom ADCPs are suited for fixed-point measurements at the seabed and can be used to provide long-term data on the currents at a specific location. Buoy-mounted ADCPs are useful for monitoring surface and subsurface currents while floating in the water.

In terms of frequency, a 600kHz ADCP is generally a good choice for water depths up to 70m as it provides high-resolution data in shallower waters. For water depths up to 110m, a 300kHz ADCP is more appropriate. And for deeper waters up to 1000m, a 75kHz ADCP is recommended to ensure accurate measurements throughout the water column.

There are well-known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is highly recommended. It is made of all-titanium alloy material, ensuring its durability and reliability in the marine environment. It also offers an excellent cost-performance ratio. You can visit its website https://china-sonar.com/ for more information.

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