How can we measure Ormara's coastal currents?

1. Where is Ormara?

Ormara is a costal town in the Balochistan province of Pakistan and is located on the Arabian Sea coast. The town is basically known for its natural beauty, with clear blue waters and sandy beaches.

Ormara is a very rich area in terms of culture. Most of the people of the area are fishermen. Their lives have been associated with sea-based activities. This place is strategic in the sense that it is a sea-facing town. There are Arabian Sea waters off Ormara's coast, host to a number of species of marine life. It hosts all kinds of fish, crabs, and other shellfish. The water route is used for transportation by small fishing boats and some bigger vessels also use this route.

2. What is the condition of the coastal currents off Ormara?

The general coastal currents off Ormara have various origins; most important of these sources is that of monsoon winds. Southwest monsoon, June-September, gives strong wind, which can push surface waters and alter the coastal current's direction and velocity. Such winds can be very helpful in giving rise to various patterns of currents.

Then again, there are tidal forces. Tidal forces are important and are the gravitational pull of the moon and sun, causing the tides and sometimes strong tidal currents. The shape of the coastline and topography of the seabed may have an influence on how tidal currents flow, while various submarine features such as sandbars and channels can thus alter the direction of water movement.

Besides, the mesoscale ocean circulation patterns of the Arabian Sea can interact with the local coastal currents. The inflow of different water masses from other regions brings changes in temperature, salinity, and overall characteristics of the coastal currents.

3. How to Observe the Coastal Water Flow of Ormara?

Surface Drift Buoy Method: This is a method where buoys are deployed on the water surface. These buoys are designed to drift with currents. Employing satellite-based tracking systems or other means for positioning over longer time periods yields information on the direction and speed of the surface currents. However, this system yields data mostly from the surface layer and may not be complete with respect to the current distribution at various depths.

Anchor Boat Method: This is a procedure in which a boat is anchored in coastal waters. The flow of water at various depths around the boat is measured with the help of instruments. It may give further detail to the area of surroundings of the boat. However, it is comparatively more labor- and time-consuming. Also, it has its limitations as regards the area it can cover.

One of the newer, more functional ways of measuring coastal currents is by Acoustic Doppler Current Profiler(ADCP). The principle behind it is to measure simultaneously the velocity of water at different depths by using sound waves. It works by emitting sound pulses and then analyzing the Doppler-shifted reflections that return from particles in the water to create a profile of the current from the surface down to a given depth. This gives a more accurate picture and broad coverage of the currents of the coast when compared with the other approaches.

4. Principle of Working of ADCPs Employing Doppler

They operate by employing the effect called the Doppler Effect. Sound pulses are produced in the water by these. Consequently, while being absorbed by particles in the water-sediment particles, plankton, or simply any other type of particles, due to the Doppler effect, these sound waves already have a frequency different than that of the emitted sound waves. In other words, when the aforementioned sedimentary particles are moved toward an ADCP, the received reflected waves become of a higher frequency than those that were sent; vice versa when such sedimentary particles are moving away.

The ADCP calculates the velocity of the water in different directions based on the frequency shift of the reflected sound waves at various angles and depths. Several transducers are mounted to transmit and receive these sound signals with the ADCP; hence, it is able to develop a rather complex profile of the water velocity throughout the water column from the surface to a specific depth, depending on the instrument's capability.

5. What does the high - quality measurement of Ormara coastal currents call for?

The measuring equipment deployed in the coastal currents off Ormara should be manufactured with durable materials which would survive the harsh marine conditions due to salt-water corrosion, temperature fluctuations, and any possible physical impacts from floating debris.

The size of the equipment should be small in size for easy deployment and installation. Whether on boats, buoys, or even at the seabed, a small size makes handling and installation easy. It also makes transportation and maintenance more convenient.

In the case of floating and moored devices, for example, the weight should be light in particular, with a light enough weight to assure adequate buoyancy and stability. Low power consumption is also very vital; this will enable longer operation continuously without seeking frequent replacement of batteries or any heavy power supply.

Other factors considered are cost-effectiveness. Equipment for large-scale measurement along the coast should be fairly cheap. A good option for the casing of the ADCPs is made from the alloy of titanium. In a salty marine environment, its corrosion resistance is outstandingly excellent. In addition, it is strong enough yet lightweight for high-quality equipment that measures currents.

6. How to choose the appropriate equipment for current measurement?

The equipment for the measurement of current at Ormara should be chosen keeping the purpose of its usage fore. 

Ship - borne ADCP :It would serve ideally for measurements over a moving vessel. In the case of recording coastal currents continuously as the ship travels along the coast, therefore a series of points it gives out would be found to cover a relatively wider area covered by the path covered by the ship route.

Bottom-mounted ADCP: Can be used for fixed-point measurements from the seabed. Provides a very stable and long record of the water flow near the bottom, of crucial importance for understanding the interaction of the bottom topography and the coastal currents.

Where the measurement of the area currents needs to be done by floating over the water for extended periods, the ADCP mounted on a buoy is used. It can easily be installed in the study areas for continuous measurement since it need not occupy a vessel all the time.

In order to obtain water depth frequency within 70m, the 600kHz ADCP would be highly favorable while for water depths as shallow as 110m, a 300kHz ADCP will be applied. For water as deep as 1000m, a 75kHz.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth mentioning. It has a casing made entirely of titanium alloy and offers an excellent cost - performance ratio. You can find more information about it at https://china-sonar.com/.

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