ADCP Application to Ocean Current Measurement in the Port of Salina Cruz

1. Where is Salina Cruz port?

Salina Cruz port is on the Pacific coast of Mexico, state of Oaxaca. It is a strategic and important port that plays an important role in the maritime trade of the country as well as in the regional economic activities.

Port Scale and Throughput It is a jumbo-sized port that deals in almost all types of cargo. It is exceptional in the national and international context of trade. Its annual throughput consists of bulk commodities, which also cover petroleum products, coal, and grains. Moreover, a sizeable chunk of containerized traffic also passes through it, thereby making it a vital channel in the importation and exportation of different kinds of goods. This is to ensure the management of such a large quantum in the best manner possible at this port.

Routes and Business Salina Cruz port is connected to most of the ports in Mexico, as well as a variety of international shipping routes. It has strong trade links with several ports in the Americas, Asia, and other regions. The business engagements include imports of machinery, electronics, and consumer goods that support local industries and the domestic market. Most of the exports from the port are local agricultural products, minerals, and processed goods.

Port Management and Operation The port is managed on the principle of safety and efficiency. Its management oversees everything in the operations, from cargo handling to vessel docking and security. Stringent safety regulations and procedures are put in place to make sure that workers are safe and the environment is protected within the port area. This port also cooperates with local businesses, shipping companies, and government agencies for maximum efficiency in its operations for regional economic benefit.

Port Facilities It has modern and well-maintained facilities. It has long quay walls with several berths that accommodate various vessels, from small fishing boats to big container vessels and bulk carriers. It is fully equipped with advanced handling facilities for containers and bulk cargo: cranes, conveyor belts, and storage areas. Additionally, it provides other auxiliary services, including fueling stations, facilities for the repair of ships, and supplies of fresh water and electricity to vessels.

Channel and Navigation The channel to the port is dredged to allow safe access by vessels. Buoys, light, and radar systems serve to guide vessels in and out of the port. This enables speedier and more direct navigation even under bad weather or tidal conditions.

2. Why measure ocean currents in the Salina Cruz port?

• Optimizing Vessel Navigation In this regard, there is a need for ocean currents measurement at the Salina Cruz port for better navigation of vessels. Currents within the Pacific Ocean are often a concern to many a ship when it comes to its speed, course, and even fuel consumption. With good data regarding the currents, captains may plot their travel accordingly and use the beneficial ones that would reduce fuel and travel time. For example, when arriving or leaving the port, taking into consideration that the current is, in fact, and where, enables more precise maneuvers without as much risk of collision or running aground.
• Protection of Port Structures The quay walls, berths, and other underwater structures comprise the structure of the port that invariably faces the current of oceans. With time, these strong or unpredictable currents erode, scours, and even causes structural damages. Current monitoring will help port authorities in identifying the areas of most vulnerability and thus taking some preventive measures, such as reinforcement of the structures, adjustment in dredging schedules. All these things help in safeguarding the port infrastructure and prolongs its life.
• Effectively Manage Marine Environment Ocean currents are a concern in the management of the marine environment at the port. Currents allow for the dispersion of pollutants, sediments, and heat. The study of currents would permit control to be undertaken for contaminant distributions, manage deposition processes, and protect aquatic ecosystems accordingly. This will be useful in the context of marine environmental health and legislative requirements.

The measurement of ocean currents by Acoustic Doppler Current Profiler(ADCP) has been more advanced and at ease compared to conventional techniques. It can also offer very detailed and real-time information on the speed and direction of currents of different depths inside the port. This would allow informed decisions to be made for port operations and environmental protection.

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

The principle of ADCPs is based on the Doppler effect. They emit acoustic signals into the water. In fact, the acoustic waves interact with the particles carried by the ocean currents: suspended sediments, plankton, and other small organisms.

The acoustic waves emitted by the current meter bounce back, after striking the moving particles due to the Doppler effect, at a changed frequency of the reflected waves. The ADCP measures the difference in the frequency of the emitted and the received signal. Through a series of complex algorithms, it calculates the velocity of the moving particles. Further, this velocity information gets translated into the speed and direction of the ocean currents.

In the context of Salina Cruz port, the two main ways of using ADCPs are as follows:

Ship-borne ADCP A ship-borne ADCP is installed on a vessel that may be a fishing boat, cargo, or survey vessel. The ADCP operates with the movement of the boat in continuous mode around the port area and its adjunct waters by sending and receiving acoustic signals. The overall data collected will give detailed information on the current pattern in different parts of the port and its surroundings where the vessel travels.

Fixed ADCP One bottom-moored ADCP can be deployed on the seabed near a port entrance or at any other key location. It will keep the current condition at that very point continuously. The advantages are long-term, stable data on local current characteristics quite necessary for understanding the regular flow of currents and therefore detection of any unusual changes in them.

4. What is needed for good measurement of the Salina Cruz port currents?

• Durable and Reliable Materials The materials used for the current measurement in the Salina Cruz port should be able to operate in harsh marine conditions. Seawater contains corrosive properties, and the deployment depth may cause the instrument to face pressure variations. Therefore, corrosion-resistant and durable materials are developed to guarantee quality and repeatability in measures.
• Compact Size and Light Weight Another key factor would be the size and weight of the equipment. In this regard, an ADCP for this application should be small in size, since space is very constrained at a port and installations on vessels must be accommodated easily. Besides, lightweight designs, especially ship-borne ADCPs, do not affect the stability and handling of the vessel as much.
• Low Power Consumption Low power consumption is important, especially for fixed ADCPs, which need to operate for long periods of time. Beyond the obvious cost savings, reduced power consumption simplifies the power supply requirements and improves equipment reliability over the long term.
• Titanium Alloy Casing It is highly recommended to make the casing of the ADCP from a titanium alloy. The corrosion resistance of the titanium alloy is excellent, making it very suitable for the marine environment. Besides, it has a high strength-to-weight ratio, thus allowing for a durable but relatively lightweight design. This will enable the ADCP to bear the pressures and impacts that it may encounter in port waters.

5. Choice of Suitable Instrument for the Measurement of Current?

Dependency on Scenario of Use

• Ship - borne ADCP: In cases where an area of wider range-ground of the port and the surrounding waters is to be surveyed, a ship - borne ADCP will suit the deal. It shall be useful in fishing trips or while on routine surveys at a port to take current data across a wide area.
• Bottom-mounted (sit-on-bottom) ADCP: Long-term and stable current monitoring at given locations, such as entrance of the port or at locations near important berths, calls for a bottom-mounted ADCP as appropriate. In this case, continuous information is made available about the local condition of the current.
• Buoy-mounted ADCP: When the measurement point needs to be more flexible and movable, then a buoy-mounted ADCP is applied. It can be installed in various areas of the port waters, depending on the specific requirements.

Frequency Selection

• Up to 70m of water depth, 600kHz ADCP is quite suitable.
• Up to 110m, the ADCP frequency should not exceed 300kHz.
• A 75kHz ADCP would be more accurate for waters as deep as 1000m.

There are well - known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all - titanium alloy material, ensuring its durability and performance in the marine environment. It also offers a great cost - performance ratio. You can find more information on its website: (https://china-sonar.com/).

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