How do we go about measuring the coastal currents in Jiwani?

1. Where is Jiwani?

Jiwani-for all one knows-is a small coastline village in the Balochistan province of Pakistan; this is on the coasts of the Arabian Sea; there it remains a popular tourist sport mainly because of its immense and usually less disfigured beaches.

It is a city that belongs to the territory with a specific cultural legacy. In Jiwani, the majority of the inhabitants are engaged in fishing and other sea-related professions. The landscape around Jiwani is a mixture of arid plains where the vast expanse of the Arabian Sea opens up. The sea is an inseparable component of the local economy and everyday life.

The Arabian Sea, lying next to Jiwani, hosts a variety of marine organisms. There are different types of fish, crustaceans, and mollusks. The sea also provides an important route for transportation, though it may not host as much heavy shipping in this area compared to the bigger ports. The shores have sandy beaches, and in some parts the land is made up of rocks shaped by the actions of waves and currents.

2. What is the coastal current in the coast of Jiwani?

The coastal current in Jiwani coast depends on more factors than one. This happens under the action of the monsoon winds. The strong winds that blow during the southwest monsoon-from June to September-power the surface waters influencing changes in direction and speed of coastal currents; therefore these winds might create several current patterns.

The tidal forces are not negligible either. The tides are the result of the gravitational pull by both the moon and the sun, and the tidal currents accompanying this may be rather strong. The shape of the coastline and the topography of the seabed may affect the way the tidal currents flow. Submarine features as sandbars and channels can cause the water to divert.

In addition, the coastal currents of the region of the Arabian Sea may interact with the large-scale ocean circulation patterns. The inflow of more water masses from other regions can bring changes in temperature, salinity, and overall characteristics to these coastal currents.

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

Surface Drift Buoy Method: This is one of the methods employed whereby buoys are deployed on the water surface. These buoys are designed to drift with the currents. Over time, the movement of these buoys could be followed using satellite-based tracking systems or other positioning methods for data on the direction and speed of surface currents. This mainly provides data for the surface layer and may not give an accurate understanding of the currents at different depths.

The second anchor boat method involves positioning a boat in the middle of coastal waters and then, through the use of instruments, measuring water flow from various depths around anchored boats. Thus, it can provide more detailed information for the area around it, but normally this is a rather labor-and time-consuming method. It covers fewer grounds, too.

ACDP stands for Acoustic Doppler Current Profiler. The principle of ACDP is more scientifically intensive and hence works more effectively in the measurement of currents. It utilizes sound waves in determining the speed at which water moves at a variety of depths simultaneously. By emitting sound pulses with the analysis of the Doppler-shifted reflections from particles in the water, this system enables the creation of a detailed profile of the current from surface to a certain depth. This gives a closer and broader view of the coastal currents than the other methods.

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

The working of ADCPs is based on the principle of the Doppler effect. They send pulses of sound into the water. These sound waves, in their interaction with the water particles-sediment particles, plankton, or any other small organisms-produce a shift in frequency of the reflected sound waves due to the Doppler effect. If the particles are moving towards the Acoustic Doppler Current Profiler(ADCP), then the frequency of the reflected waves is higher than that of the emitted waves; if they are moving away, the frequency of reflected waves is lower.

It measures the frequency shifts of the reflected sound waves at various angles and depths to determine the water velocity in various directions. It sends and receives these sound signals with a set of multiple transducers that enable the ADCP to create a detailed profile of the water velocity throughout the water column from the surface down to a certain depth, depending on the capability of the instrument.

5. What is required for the measurement of the Jiwani coastal currents to high quality?

For measuring coastal currents off Jiwani, equipment made from very reliable material is required since the marine environment is so harsh, causing salt-water corrosion, sudden changes in temperature, and even physical impacts brought about by floating debris.

The size of the equipment should be small enough to easily be deployed and installed either on boats, buoys, or at the seabed. This will be easier in handling and installing processes, not to mention easier in transportation and maintenance.

Since many of them have to be floating or moored, the weight must have been light, while related, the weight has to assure that this device has good buoyancy and stability. The whole must have low power consumption since most applications require continuous operation during hours and days without exchanging a lot of batteries or unusual power supply.

Cost-effectiveness is very important. To perform measurements on a large scale along the coast, the equipment must be reasonably affordable. In the case of an ADCP, casing made of titanium alloy is an excellent choice. The corrosion resistance of the titanium alloy is great, which is so important in the salty marine environment. It is strong and at the same time relatively light and meets the requirements for high-quality current-measurement equipment.

6. How to Select appropriate equipment for current measurement?

While selecting equipment for current measurement off Jiwani, the very first thing to be considered is the purpose of usage.

Ship - borne ADCP: This is suitable for measurements from a moving vessel. It can 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: Can be applied for fixed-point measurements on the seabed; this provides a more or less continuous long-term record of the water flow close to the bottom, potentially highly relevant for bottom topography interactions with coastal currents.

Buoy-mounted ADCP: When the purpose is to measure the currents of an area over a long period while floating on the water surface, the buoy-mounted ADCP is used. It can be deployed in areas of interest and provide continuous data without requiring a vessel to be present all the time.

For water depths within 70m, a 600kHz ADCP will suffice. For larger depths up to 110m, a 300kHz ADCP is better. For deeper waters still, up to 1000m, a 75kHz ADCP is recommended.

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.