ADCP's Application to Ocean Current Measurement in Karachi Port

1. Where is Karachi Port?

Karachi Port, with its privileged position on the southern coast of Pakistan, along the Arabian Sea coastline. It lies southwest of the Indus River Delta, making the port a primary entrance to both Pakistan and South Asia as a whole.

Port Scale and Throughput

Karachi Port is one of the leading and largest deep-water seaports in South Asia. It has a considerable annual throughput, with a large volume of cargo that ranges from a variety of cargo types. It handles about 60% of the total merchandise, around 650,000 twenty-foot equivalent units of containerized cargo, and 26 million tons of bulk and general cargo that pass through the country every year. This manifests the role of this port as far as the trade and other economic activities within Pakistan are concerned.

Routes and Business

The port happens to fall alongside the major shipping routes internationally. An example could be the Strait of Hormuz, among other navigation channels essential in connecting the Middle East to Africa and Europe with their Asia counterparts. Regular shipping lines operate to connect Karachi Port to practically all the great ports worldwide. The port imports and exports a variety of commodities. The export commodities include rice, wheat, and textiles, while the imported commodities are petroleum products, machinery, and chemical products. It also provides gateway services to the Central Asian Republics, adding to its regional importance in international trade.

Port Management and Operation

The port is run by the Karachi Port Trust, which has been in charge since 1857, and operates day and night, 24 hours a day, seven days a week. The KPT ensures safe navigation for vessels of all types, such as tankers, container vessels, bulk carriers, and general cargo ships. It regulates various aspects of port operations, from berthing arrangements to cargo handling procedures, and enforces standards for safety and regulations.

Port Facilities

The Karachi Port is 11 km long with deep water, having an unobstructed and safe channel for navigation of vessels of tonnage up to 75,000-ton displacement. In this port, there are three docks: the East Wharf, West Wharf, and South Wharf, altogether with a total number of 34 berths. To be specific, it has 17 berths in the East Wharf, 13 in the West Wharf, and 4 in the South Wharf. Besides that, there are three liquid cargo terminals dedicated for handling petroleum products and other liquids.

For repair and maintenance of ships, it also has dry docks.

Waterways and Direct Navigation

Waterways around the Karachi Port are dredged and marked for smooth navigation. It keeps the main navigational channel to adequate depth for the safe ingress and exit of large-scale vessels. The port is well-connected with main cities, industrial zones, and agricultural areas inside Pakistan through an extended network of roads and railways. It is also about 13 km from the airport, where regular flights connect to various parts of the world, thus making this port more connected in terms of multi-modal transportation.

2. Why is it important to measure ocean currents in Karachi Port?

Safety of Vessel Navigation

Ocean currents are highly influential factors that affect the movements of vessels operating within Karachi Port. The current can cause variation in a vessel's speed and course besides influencing its berthing operations. Powerful currents have a tendency to cause a ship to veer away from her track, posing danger to hitting another vessel or a port facility/structure and/or shallow grounds. Accurate monitoring of the currents will avail ship captains with the latest information for making prudent decisions. They will thus be able to make proper changes in navigation: speed, direction, and maneuvers for berthing to ensure safe passage of their vessels through the port.

Cargo Handling Operations Optimization

Understanding the ocean currents is very important in optimizing cargo handling operations at the Karachi Port. Currents affect the stability of vessels during cargo loading and unloading. For example, strong currents may impact on the exact positioning of cranes or poor alignment of equipment employed in the transfer of cargo. With the aid of the current patterns, port operators would make better scheduling of cargo-handling activities and, hence, reduce downtime periods. In this way, the turnaround times for ships become quicker hence increasing the number of ships going through the facility.

The data of ocean currents are important for the design, construction, and maintenance of the port facilities in Karachi Port. Currents give rise to sedimentation and erosion that may be very destructive for the stability of docks, breakwaters, and other structures. Long-term studies of ocean current patterns can provide engineers with knowledge on how to make port facilities more resistant to these natural forces. Besides, the present-day measurements can indicate areas where sedimentation is most likely to occur and thus facilitate dredging in due time to maintain the depth of navigation channels at the required level. This in turn cuts down on the cost and effort involved in maintaining the port for long-term operability.

Protection of Marine Environment

The marine environment of Karachi Port is a sensitive ecosystem. Large distances can be covered by ocean currents, which carry pollutants such as oil spills, industrial waste, and sewage. Environmental managers can predict the spread of these pollutants by measuring the currents and take proactive measures to mitigate their impact. This may include deploying containment booms, conducting clean - up operations, or implementing strict environmental regulations. Knowledge of the prevailing pattern further helps in the protection of sensitive marine habitats, which may be important not only for biodiversity but also for protection of coasts, such as coral reefs and mangroves.

Among the various methods available to measure ocean currents, ADCPs have emerged as one of the most advanced and convenient options. Real-time data is obtained with high resolution, hence offering a more realistic overview of the characteristics of ocean currents compared to traditional methods.

3. How do ADCPs using the Doppler principle work?

Measurement Principle

Working principles of ADCPs are based on the Doppler effect. This device emits sound waves of known frequency into the water column. While moving in water, the acoustic signals also catch onto some small particles of plankton, sediment, and air bubbles in water moving with the flow of current. These catch onto the moving particles; the acoustic signals get reflected back, changing their frequency in signals as they are received by the ADCP.

The Doppler effect states that if the source of a wave in this case, the ADCP's acoustic transmitter and the observer-the ADCP's acoustic receiver-are in relative motion, the frequency of the received wave will be different from the transmitted frequency. The magnitude of this frequency shift is directly related to the velocity of the moving particles and thus the water current. With precise measurement of the frequency shift, the ADCP profiler can compute the water current's velocity magnitude and direction at various levels within the water column.

ADCP in Port Current Measurement-Specific Methods

Ship-borne ADCP

The ship-borne ADCP is fixed onto a ship by way of either a hull-mounted transducer or by a lowered acoustic head. One ADCP current meter continuously measures ocean currents beneath the ship as the latter travels through the water. This technique is helpful in carrying out big surveys of the port area and its surrounding waters. Ship-borne ADCPs are able to cover an extensive area quite fast and thus allow one to view an overview of current distribution. They are often used for initial mapping of current patterns or monitoring changes in current conditions over a large spatial scale. For example, a ship-borne ADCP can be used to survey the entire approach channels and berthing areas of Karachi Port in order to find out any major variations in the current speed and direction.

Fixed ADCP

Fixed ADCPs are installed at selected locations within the port, such as near berths, in shipping channels, or at important environmental monitoring points. Usually clamped onto some fixed structure-a piling, for example, or a buoy-these are designed to provide long-term, continuous data about local current conditions. In view of special features of the currents at the key locations of the port, fixed ADCPs become extremely important. For instance, in Karachi Port, a fixed ADCP near a busy berth can provide real-time data of the currents affecting the berthing and unberthing of ships at that particular location. Such information is very useful for the management of port operations, whereby vessel movements could be scheduled with greater accuracy along with the enforcement of necessary safety measures.

4. What is required for high-quality measurement of ocean currents at Karachi Port?

Equipment Reliability

High-quality measurement of the ocean currents at Karachi Port requires the ADCP meter to be of high reliability since the marine environment within and outside the port is hostile, composed of saltwater corrosion, high humidity, and strong waves. Material selection to make the ADCP should be of a nature to resist such conditions over a long period. The device shall contain high-quality components and a robust design so that it can continue its operation with accuracy even when environmental conditions are not favorable.

Size, Weight, and Power Consumption

The size of the ADCP current profiler must be reasonably small in order to allow easy installation and deployment. The smallest size in ship-borne ADCPs means less interaction with the normal operation of the ship. For those fixed-deployed, it guarantees ease of attachment to many structures. Besides, a light ADCP is easier to manipulate during installation and maintenance. Also, the power consumption of ADCPs should be at a minimum, especially for fixed deployments with battery power or renewable energy supplies like solar panels. This will ensure that the operations are long-term and continuous without frequent power replacements or large-scale power infrastructure.

Cost-effectiveness

The ADCP needs to be affordable to allow measurement of the currents in Karachi Port on a large scale. In this respect, an affordable price for the ADCP can allow several units of the same make to be mounted at different places within the port for a wider understanding of the pattern of the currents. This is pretty important in a big port like Karachi, which may have different areas with different characteristics of currents. Being able to afford multiple ADCPs enables port authorities to get a finer and more accurate picture of the ocean currents, which is what is really required for effective port management.

Titanium Alloy Casing

The casing of the ADCP flow meter is preferably made of titanium alloy. Titanium alloy offers several advantages in the marine environment. First, it has excellent corrosion resistance in saltwater, essential for the long-term durability of the ADCP. Unlike other metals, the titanium alloy will not corrode or rust, even under extreme conditions such as those posed by the salt-laden waters of Karachi Port. Second, the titanium alloy is relatively lightweight, which benefits ship-borne and fixed-deployed ADCPs. It has very high strength with lightweight to bear the mechanical stresses associated with the ADCP operation in a port environment. These properties of titanium alloy make it an ideal choice for the ADCP casing, ensuring reliable and long-lasting performance.

5. How to Choose the Right Equipment for Current Measurement?

Based on Usage

• Ship-borne ADCP: The ADCP is highly suited for very large-scale surveys of the whole port and adjacent waters. An ADCP working during vessel motion may cover very large study areas, thus delivering a general outline of currents. Ship-borne ADCPs are very often used in initial mapping exercises where one wants to have an idea of the general current distribution in the port area. A ship-borne ADCP can also be utilized in the planning phase for the new expansion of Karachi Port with the aim of mapping the entire area and finding those potential areas which may develop high-velocity current or complicated patterns.
• Sit-on-bottom ADCP: The ADCP is designed to be deployed directly on the bottom of the seabed in a certain location. It is ideal for long-term, continuous monitoring of currents at a particular point. In Karachi Port, the sit-on-bottom ADCPs can be placed in important shipping channels or near critical port structures, such as breakwaters. Data collected by these fixed-location ADCPs helps in analyzing long-term trends within current conditions that are useful to predict sedimentation, erosion, and the effect of currents on port structures.
• Buoy-mounted ADCP: The buoy-mounted ADCPs are those attached to the buoys floating on the water surface. They can provide valuable information about surface-level currents, as well as currents at different depths, depending on the length of deployment of the sensor. Bottom-mounted ADCPs cannot be used where strong tidal currents are expected or in the open-water regions near the port; buoy-mounted ones are useful for monitoring currents there. They can be used in Karachi Port to study the interaction between the internal currents of the port and the larger-scale ocean currents in the Arabian Sea.

Based on Frequency

• 600kHz ADCP: An ADCP with a frequency of 600kHz is suitable for measuring currents in water depths of up to approximately 70m. This frequency gives relatively high-resolution data and thus is quite suitable for use in relatively shallower waters. In Karachi Port, the 600kHz ADCPs can be used in berthing areas, nearshore, or in parts of the port that are relatively shallow. The high-resolution data provides an effective way to determine the currents in these areas with better accuracy, important for vessel berthing and maneuvering.
• 300kHz ADCP: This shall have a correct depth range, of approximately 110m or so, blending the needs and resolution in proper depth coverage. This can act in regions that are relatively not too shallow; thus, also deeper in regards to water, than that is covered by a 600 kHz ADCP current profiler. For instance, an ADCP of 300kHz is operable for reliable current data over sections where the water depth is between 70 to 110m in some parts along the main shipping channels of Karachi Port.
• 75kHz ADCP: Operable in deeper waters up to about 1000 meters. Although it has a lower resolution compared to higher-frequency ADCPs, it can cover greater depths. In the outer areas of Karachi Port or in the deeper parts of the Arabian Sea near the port, a 75kHz ADCP can be used to measure the deeper-layer currents, which are useful to know about the general ocean circulation pattern and its effects on the port.

There are a few well-established ADCP brands in the market, including Teledyne RDI, Nortek, and Sontek. The brands mentioned above signify high-quality products with advanced technologies. However, the Chinese brand, China Sonar PandaADCP, is highly recommended for those in need of cost-effectiveness and reliability at the same time. Made of all-titanium alloy materials, it offers excellent corrosion resistance, which is especially important for use in the marine environment of Karachi Port. With an impressive cost-performance ratio, it provides a great solution for ocean current measurement in the port. You can visit their website at (https://china-sonar.com/) for more information.

Here is a table with some well known Acoustic Doppler Current Profiler(ADCP) instrument brands and models.