How to Measure Kish Coastal Currents

1. Where is Kish?

Kish is an attractive island in the Persian Gulf and it forms part of the territorial waters of Iran. The island is renowned for its lovely beaches, posh resorts, and vibrant tourism. It enjoys a pleasant climate since it boasts warm temperatures for almost all seasons of the year and attracts both natives and foreign tourists.

Surrounded by the glistening waters of the Persian Gulf, Kish has a very unique marine environment. The gulf waters around the island host different types of marine life, including colorful fish species, different types of crustaceans, and attractive coral reefs. Most areas on the island are pretty flat, with some gentle slopes that reach down to the coastline.

Geographically, Kish is positioned along key marine routes in the Persian Gulf, hosting a busy port for trade and transport. This whole area is subjected to overall current circulation patterns within the gulf, modified locally by island topography and winds over it.

2. What is the state of the coastal currents close to Kish?

Some of the major causes of coastal currents near Kish are as follows: Tidal currents play a significant role in the development. The gravitational pull of both the moon and the sun generates tides in the Persian Gulf, thus creating an ebb and flow of water along the coast of Kish on a regular basis. These tidal currents may differ in strength and direction according to the lunar phases and the specific bathymetry around the island.

The wind-driven currents also play their role. The prevailing winds of the area can push the surface waters to develop surface currents interacting with tidal currents. In many areas, the stronger winds of certain seasons bring about pronounced patterns in the surface currents. Monsoon winds, for instance, may have a marked influence on coastal circulation.

Moreover, the underwater topography around Kish exerts a great impact on coastal currents. The underwater ridges, channels, and variable depth may turn and change the flow of water. Generally speaking, shallow areas may slacken the currents, but on the contrary, the deeper channels can give speed to them, forming in this way a current regime near the coast of this island, which is so complicated and dynamic.

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

Surface Drift Buoy Method: The buoys are set free on the water surface, allowing them to drift freely with the currents. By tracing the position of the buoys in time with the use of satellite or other positioning systems, some valuable information on the direction and speed of the surface currents can be obtained. However, this method mainly concerns the surface layer and does not give detailed insight into the vertical structure of the currents.

Anchor Ship Method: It involves anchoring a ship in one position near the coastline of Kish. Current meters along with other instruments that are on board will then measure the flow of water around the anchored ship. Although it can provide more or less accurate data from the immediate area around the anchored ship, it has limitations with regard to covering a large area and different depths simultaneously.

Acoustic Doppler Current Profiler (ADCP) is more advanced and efficient in its measurement. It sends acoustic pulses into the water and analyzes the Doppler shift of the reflected signals from moving water particles. This enables it to measure the velocity of water at multiple depths within the water column, providing a comprehensive understanding of the vertical profile of the coastal currents. Compared to the other methods, ADCP current meter offers higher accuracy and the ability to continuously monitor the currents over extended periods.

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

These instruments, or ADCPs, use the principle of Doppler. Equipped with transducers, they shoot acoustic pulses into the water. When these pulsations reach the moving water particles, the frequency of the reflected waves changes due to the Doppler effect. By precisely measuring this change in frequency, the speed of the water particles relative to the ADCP profiler is calculated.

In general, there are multiple transducers inside an ADCP meter that send acoustic signals in various directions. That might be one of the reasons for acquiring the three-dimensional water current velocity: the east-west direction, the north-south direction, and vertical direction. Those kinds of time-of-travel and sound waves going forward from the transducer to the water particles and back will also be recorded. By using this information together with the Doppler frequency shift, the ADCP can accurately calculate the speed and direction of water flow at different depths within its range.

5. What's required for high-quality measurement of Kish coastal currents?

The following are the requirements necessary from the measuring equipment to have high-quality measurements of coastal currents near Kish.

These instruments shall be constructed with the use of more reliable materials to tolerate this harsh marine environment: salts in water, extreme temperatures, and a possible flow of litter within. The equipment should also have smaller dimensions and weigh lighter for better deployment on vessels or at fixed points intended for monitoring purposes.

The power consumption is to be low, above all, for operations where long-term monitoring needs are required. This makes equipment operate for a continuous period without replacing batteries or the use of immense power sources. Further, low cost opens up more uses and the possibility for deploying many units for a higher density measurement network.

The material used in making the casing for an ADCP flow meter can be a titanium alloy. For working in salty waters, especially in the Persian Gulf, titanium alloy will provide very good resistance to corrosion. While strong and light, the high ratio of strength to weight enables a robust but lightweight design. Further, it can withstand high pressures associated with different levels of water depth.

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

In selecting the proper equipment for current measurement in Kish, a number of aspects have to be considered.

Depending on the purpose of use, there are varieties of ADCPs that can be used.

Shipborne ADCPs are designed to be installed on ships, and thus the measurement is possible while the ship is moving. They are good for covering a large area of the coastal waters by traveling the ship.

The measurements from bottom-mounted ADCPs have been fixed on the seabed and have given continuous and steady measurements of the currents passing above them. In fact, for long-term monitoring at fixed locations, the idea is great. Buoy-mounted ADCPs were attached to floating buoys, joining the mentioned advantages with the capability to measure in different areas with less effort during deployment and recovery.

In general, frequency selection depends on water depth. In water as deep as 70 meters, 600 kHz ADCPs are often a good option, since it is able to give high resolution in relatively shallow areas. The 300 kHz type would be appropriate for depths of up to 110 meters. In deep waters, say as much as 1000 meters in depth, an ADCP of 75 kHz is advisable to measure over a large vertical range with accuracy.

There are several famous ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, for a cost-effective option with good quality, one may refer to the China Sonar PandaADCP. It is an all-titanium alloy-made device with an unbelievable cost-performance ratio. Check it out on its official website: https://china-sonar.com/.

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