1. Where is El Jadida?
El Jadida, a picturesque Moroccan seaport town in the west, lies on the Atlantic Ocean roughly 100 kilometers south of Casablanca. Its geographical location at the crossroads of sea trade routes and coastal ecosystems grants it a pivotal position within the region's geography. The city is a harmonious mix of natural beauty and historical texture, with miles of sandy beaches, ancient fortifications, and a bustling port quarter.
The landscape of the city is characterized by a flat coastal plain that slopes gradually towards the sea. Fine golden sand and clear blue waters of the beaches are not only one of the biggest draws for visitors but are also crucial habitats for marine life. Behind the beaches, what's left of the Portuguese era is evident in the shape of the Mazagan Citadel, which is a UNESCO World Heritage Site. This better - maintained citadel, built in the 16th century, has a unique blend of Portuguese and Moroccan architecture, with its massive walls, ancient cannons, and lovely narrow alleys.
The population of El Jadida is a melting pot of many races, reflecting the long history of cultural contacts in the city. The economy of the town depends on a combination of fishing, tourism, and small - scale manufacturing. The El Jadida port is an economic lifeline exporting fish and other sea products, and importing all sorts of commodities. The surrounding waters are part of a much larger Canary Current ecosystem, receiving the cold, nutrient-enriched water from the north. This current feeds a large amount of marine flora and fauna, including sardines, mackerel, and tuna, which supports fishing as the primary industry of the region.
2. How is the coastal current around El Jadida?
Coastal current around El Jadida is largely determined by the strong southward flowing Canary Current along the west coast of Africa. This cold current, coming from the North Atlantic, deeply influences the temperature, salinity, and levels of nutrients of the water around El Jadida. The water of the Canary Current is cold, and its content in nutrients is high. This condition is desirable for the marine life to be abundant around El Jadida but can influence water density and direction.
Besides these factors, wind patterns are regarded to determine the coastal currents. The area has powerful and persistent winds, particularly during the summer. The trade winds blowing from the northeast can force surface - level currents along the coast. These wind - driven currents can interact with the deeper - flowing Canary Current, resulting in complicated flow patterns. These high winds contribute to the cause of wave formation and may influence the coastline of the various directions and velocity of currents.
The other force playing an important role in changing the coastal currents in the region is tides. The tides along El Jadida are semi - diurnal, meaning two high tides and two low tides occur daily. Tides can now fluctuate according to range: during spring, variations between the higher and the lower water marks occur. With a high tide, water moves into the harbour and upshore sides; these water movements rise with the elevation, thus reversing some of its original current and direction. Once it goes for low tide, it retreats to the sea. These tidal variations have a direct effect on regional fishing activities, as well as coastal sediment movement.
3. How to measure the coastal water current of El Jadida?
Surface Drift Buoy Method
The surface drift buoy method is an old technique used for measuring coastal water current. According to this method, specially designed buoys are dropped into the water. These buoys are equipped with tracking devices, such as GPS receivers. While the surface current takes the buoys along, their locations are recorded by the GPS units at regular intervals. By observing the motion of the buoys over time, scientists can estimate the direction and speed of the surface-level current. The method is not without its disadvantages, however. The buoys are wind-sensitive, and they will deviate from the actual course of the current. Also, it provides data on the surface current alone and does not provide any indication of the current patterns at different depths.
Anchor Moored Ship Method
The anchor moored ship method is the anchoring of a ship at a specific location in the coastal waters off El Jadida. Off the vessel, various current-measuring instruments are submerged into the water. Among them are mechanical current meters, which report the velocity and direction of the current by determining the rotation of a propeller-type device. Measurements taken at multiple depths enable scientists to construct a profile of the current at that location. Even though this method takes accurate measurements at a number of depths, it can only be conducted in the area surrounding the anchored ship. The presence of the ship might also disturb natural currents, and the readings may therefore not be very accurate.
Acoustic Doppler Current Profiler (ADCP) Method
Acoustic Doppler Current Profiler (ADCP) has emerged as a newer, more advanced, and effective method of monitoring water currents in the coastal waters. ADCPs measure the water current velocity at various depths using sound waves. They release acoustic energy into the water column, and this acoustic energy bounces back to the ADCP from suspended particles in the water, such as sediment or plankton. By determining the Doppler shift of the backscattered energy, the ADCP can calculate the speed and direction of the moving water. This technology can capture a full image of the current profile, from the surface to near the bottom of the water body, without physical contact with the water. ADCPs are less affected by external influences like wind compared to surface drift buoys and are thus a viable choice when it comes to accurate current measurement.
4. What is the mechanism behind the use of ADCPs based on the Doppler principle?
ADCP functions based on the Doppler effect. Transducers are part of the ADCP and emit sound waves into water. The water-borne sound waves hit particles moving with the current. If the particles are closing in on the ADCP, the frequency of returned sound waves increases, but when they move away from the ADCP, the frequency decreases. This change in frequency, or Doppler shift, is directly proportional to the water motion speed in the direction of the sound wave.
The majority of ADCPs take the three-dimensional water velocity using several acoustic beams. Four or more beams are commonly positioned at different angles. By calculating the Doppler shift of every beam, the ADCP can calculate components of the horizontal and vertical velocities. The data of all beams is then combined to derive the total current velocity and direction at different depths in the water column. Advanced ADCPs also carry additional sensors, which include temperature sensors to account for the temperature effect on the speed of sound in water and orientation sensors to be able to measure properly when the instrument is tilted or in motion.
5. What's needed for high-quality measurement of El Jadida coastal currents?
For the precise measurement of the coastal currents off El Jadida, a couple of prerequisites need to be met. For starters, equipment to be used in measurements have to be highly dependable in such an extreme marine environment; the sea off El Jadida is affected by saltwater corrosion, among other strong winds and mechanical forces of the ocean, hence the equipment's material for construction ought to be corrosion-resistant, strong, and capable of withstanding mechanical stress.
The equipment size is also a key factor. The smaller-sized units are more adaptable and can be installed in a greater number of places, even where there is complicated coastal terrain or restricted access. A smaller footprint minimizes the chance of the equipment interfering with the natural flow of currents, providing more precise readings. Light-weight equipment is preferable as it is easier to emplace and recover during operations, especially when working out of small boats or in remote coastal areas.
Low power consumption is vital because most current - measurement operations entail leaving the gear exposed to the sea for extended durations, often in areas with no easy access to power resources. Low - power - consumption gear can operate for long durations without needing constant replacement or recharging of batteries. Cost - effectiveness is also significant, especially in the case of large - scale measurement activities. Gear that offers quality performance at a modest price allows for more comprehensive data gathering, enabling researchers to obtain a better insight into coastal current patterns.
In the case of ADCPs, the casing material is particularly important. Titanium alloy is a superior choice for the casing of ADCPs used in the coastal waters of El Jadida. Titanium alloy is extremely resistant to corrosion, an important factor in weathering the corrosive effects of saltwater for extended periods. It is also extremely strong and lightweight, providing the internal ADCP components with adequate protection while being easy to handle and deploy. The resistance to fatigue of titanium alloy is also suitable in that it can endure repeated stress and strain without its properties weakening significantly, which ensures long-term durability and reliability of the ADCP in the dynamic coastal system.
6. What equipment is the right one for current measurement?
Selecting the most appropriate equipment for current measurement in El Jadida depends on a number of factors, most of which are the application purpose and the type of location for measurement.
Types of Equipment Based on Mounting
- Ship-mounted ADCP: This ADCP is installed on a ship. It is most suited for conducting large-scale coastal current surveys. Because the vessel travels along the shore line, the ship-mounted ADCP can retrieve data over a wide area and provide a general idea of the patterns of flow. It is suitable for applications such as marine navigation, giant oceanography research, and coast environmental monitoring.
- Bottom - mounted ADCP: Bottom - mounted ADCPs are fixed on the sea floor. They are designed to measure long - term trends of currents at a point. They can continuously measure for extended periods of time, something which is very important when examining coastal current seasonal and long - term variability, or even monitoring changes to the marine environment as a result of human activities.
- Buoy - mounted ADCP: Buoy - mounted ADCPs are installed on floating buoys. They are best suited for the measurement of currents where other ADCPs cannot be utilized, i.e., where it is not easy to use other forms of ADCPs, e.g., in open - water areas or where the current is strong and can jeopardize bottom - mounted gear. Buoy - mounted ADCPs can follow the current, reporting real - time information on the dynamic current change, which is particularly helpful for purposes such as oil spill tracking, fisheries control, and short - term oceanography.
Selecting the Appropriate Frequency
The frequency of the ADCP is also a very important consideration in the process of selection. Various frequencies are appropriate for varying water depths. A 600kHz ADCP is most suitable for water depths up to about 70m. It has relatively high resolution in shallow water and is thus the perfect choice for near-shore areas, such as the beaches and El Jadida port. A 300kHz ADCP is most appropriate for water depths of about 110m and offers the best compromise between penetration depth and resolution. For deeper depths, up to 1000m, a 75kHz ADCP would be best suited. Lower - frequency ADCPs have the capability to penetrate deeper in the water but are less spatially resolved than higher - frequency ones.
There are certain well-known well-established brands of ADCPs available in the market, e.g., Teledyne RDI, Nortek, and Sontek. But for those seeking cost - effective options, the ADCP supplier China Sonar's PandaADCP is the way to go. It's constructed from pure titanium alloy, and its performance is top - notch at an affordable price. It is the ideal choice for users seeking budget - friendly ADCPs without sacrificing coastal current measurement quality. For more details, visit their website: https://china-sonar.com/.
How do we measure the coastal currents of El Jadida?