How would the Gwadar Coastal Current be Measured?

1. Where does Gwadar lie?

Gwadar is located in a port city and is seen towards the southern part of Western Pakistan within the Arabian Sea. In addition, it is highly important with respect to strategical or economic value.

It is a city that enjoys a privileged geographical location and as such acts for regional trade and connectivity. It is also a culturally diversified city due to the smorgasbord of ethnic groups, among which the most well-known is the Baloch people. Local inhabitants engage in fishing, activities related to the port, and other maritime trades.

The nearby Arabian Sea is immense and dynamic. Marine life is abundant, mainly different species of fish, shrimps, and other mollusks. The sea is a significant route of transportation, with the Gwadar Port being one huge infrastructural venture which definitely will increase trade between Pakistan and the rest of the world. The coastline consists of sandy beaches, rocky shores, and tidal flats. The tides are essential to the local coastal environment because they regulate the flow of water and sediments within it.

2. What is the condition of the coastal currents in the vicinity of Gwadar?

The coastal currents off Gwadar are affected by a number of factors. Most dominating among them are the monsoon winds. The southwest monsoon extends from June to September and is violent enough to provide a considerable shift in direction and speed to the coastal currents. These winds drive the surface waters and thereby give rise to different current patterns.

The tidal currents are quite significant as well. While the tides arise due to gravitational pulls from the moon and the sun, the associated tidal currents can also be quite strong. However, these may be modified around Gwadar due to the shape of the coastline and seabed topography. Bottom topography with ridges, valleys, and sandbars can change the course of water movement.

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

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

Surface Drift Buoy Method: It consists of deploying buoys on the water surface. These buoys are designed to drift with currents. With the application of satellite-based tracking systems or any other method, one will know over a certain time the movement that will give the direction and speed of surface currents. In this respect, this type of measurement basically yields data for the surface layer, and is unable to present a real understanding of the currents at various depths.

Anchor Boat Method: It is a technique used for anchoring a boat in the coastal waters. Accordingly, instruments are deployed that measure the flow of water around the boat at various depths. It could have more elaborative data than this area around the boat but it is rather time-consuming and laborsome. This also has several restrictions concerning the area covered.

The Acoustic Doppler Current Profiler(ADCP) is an advanced and efficient method of measuring coastal currents. This method adopts the measurement of the velocity of water at several depths simultaneously by making use of sound waves. It generates a detailed profile of the current from surface to a depth by emitting sound pulses and analyzing the Doppler-shifted reflections from particles in the water. This provides a fuller and better record of the currents along the coast compared to the other techniques.

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

Doppler principle-based ADCPs work on the principle of the Doppler effect. They send sound pulses into the water. These sound waves scatter off of particles in the water-sediment particles, plankton, or other small organisms-and via the Doppler effect, the frequency of the reflected sound waves is altered. If the particles are moving towards the ADCP, then the frequency of the reflected waves is higher than the emitted waves; if the particles are moving away, the frequency is lower.

The ADCP is able to calculate the velocity of the water in various directions as a function of angle and depth because it measures the frequency shifts of the reflected sound waves at different angles and depths. With multiple transducers operating in a transmit-and-receive mode, the ADCP develops a rather detailed profile of the water velocity throughout the water column from the surface down to a depth depending upon the instrument's capabilities.

5. What does high-quality measurement of Gwadar coastal currents require?

The equipment for high-value measurement of coastal currents around Gwadar should be made of reliable materials. Since the marine environment is so harsh-from salt-water corrosion and temperature fluctuations to even physical impacts from floating debris-the equipment should be robust.

Equipment size: small, for easy deployment and installation. If the deployment is at sea on boats, buoys, or even on the seabed, the smaller the size, the easier the handling and installation; it also makes transport and maintenance easier.

Weight shall not be a problem, taking into account the buoyancy and stability are very critical to floating or moored devices. Very key is also low power consumption, which needs to be able to be continuously operated over long periods of time without replacement of frequent battery sets or large-scale power.

Another important factor is cost-effectiveness. To perform widespread measurement along the coast, the cost of equipment must not be too high for the process to be effective. In the case of an ADCP, one of the best casing options is made from titanium alloy. The corrosion resistance of the titanium alloy is superb, and the material is strong, lightweight, able to cater to all the demands to be a high-quality instrument for current measurement.

6. How to Select appropriate equipment for current measurement?

While selecting the equipment for current measurement at Gwadar, the first consideration would be the purpose of usage.

Ship - borne ADCP: It is ideal for measurements from a moving vessel. It will record the coastal currents continuously as the ship moves along the coast, providing a series of data points over a relatively wide area covered by the ship's route.

Bottom-mounted ADCP: Applicable for fixed-point measurement at the seabed, providing a stable, long record of the water flow near the bottom that is of great importance in understanding the interaction between the bottom topography and the coastal currents.

ADCP mounted on a buoy: These are used whenever one wants currents at some place with respect to a certain area continuously for a long period, floating on the water surface. It can be deployed in areas of interest and thereafter provide continuous data without the vessel being present at that location every time.

A depth within 70m should use a 600kHz ADCP. Up to 110m, 300kHz ADCP would be suitable. For much deeper waters of up to 1000m, the preferred choice is the 75kHz ADCP.

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.