How do we measure the coastal currents of Ronda?

1. Where is Ronda?

Ronda is a charismatic town in the Spanish province of Málaga, part of the autonomous community of Andalusia. It is situated about 105 km west of the city of Málaga, nestled in the Ronda mountains. It is famous for its impressively located cliff face and the profound El Tajo de Ronda canyon, through which the Guadalevín River flows and cuts the town into two parts.

Ronda boasts a very ancient history. First settled by the early Celts, then a very important Roman fortified post, the architecture of the town reflects Roman, Moorish, and Spanish influences. Among the most outstanding monuments are the Puente Nuevo-a very famous bridge that spans the canyon-and the Plaza de Toros de Ronda, one of the oldest bullrings in Spain.

Speaking geographically, Ronda is enveloped by nature. Geographically, it forms part of the Sierra de las Nieves National Park and is near the Los Alcornocales Natural Park, which is famous for its cork-oak forests. Although not exactly on the sea coast, Ronda is within driving distance from the Mediterranean Sea, and its coastal waters are part of the greater marine ecosystem of the place.

2. What is the situation of the coastal currents near Ronda?

Various factors influence the coastal currents near Ronda. The general circulation patterns of the Mediterranean Sea are a significant factor. The sea's circulation is driven by a combination of wind, temperature, and salinity differences. The prevailing winds in the region, such as the Mistral and the Tramontana, can cause surface water movement and influence the direction and speed of the coastal currents.

The topography of the seabed off Ronda influences the currents, too. Submarine canyons, submarine ridges, and shallows may turn and speed up or slow down the currents. For instance, a current would decelerate where the bottom gets shallower, while in deeper channels, it may flow faster.

Though relatively small compared with other seas, tidal forces are, nevertheless, capable of displaying a measurable effect on near-shore currents within the Mediterranean. Ebb and flow can act together to push the water in and out, producing very complex current patterns when combined with other factors. Besides that, the runoff of rivers-like that of the River Guadalevín and others in that vicinity-may alter the currents of the coasts, mainly during those periods considered rainy seasons or when there is lots of snow melting.

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

Surface Drift Buoy Method

This method makes use of buoys deployed at the water surface. With attached tracking devices like GPS, while the buoy is conveyed by the surface currents, its position is recorded as time progresses. Researchers study the patterns in the surface current through the motion of various buoys. The drawbacks with this are that this is only an observation of the surface current, which may or may not indicate actual currents at other levels of depth.

Moored Ship Method A ship is moored over a position where instruments such as current meters are deployed aboard to record velocity and direction at discrete depths. Thus, it allows the details in the vertical structure of the currents more clearly. However, it is limited with respect to spatial coverage since the ship can only measure at one location at a time and the presence of the ship itself may disturb the natural flow of the water.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs measure the velocity of water currents at different depths by using sound waves. This technique offers the possibility of high-resolution, three-dimensional data on current structure. Compared with the moored ship technique, it covers a fairly broad area and is capable of simultaneously measuring currents at several depths. The ADCP current meter is, for the time being, a more advanced and convenient measurement method for the coastal currents near Ronda.

4. How Do ADCPs Employing the Doppler Principle Work?

ADCPs utilize what is called the Doppler effect principle. This tool sends out continuous acoustic pulses within the water. These sound waves then meet the water sediment, plankton, and even microbubbles. These partially return back to the transmitter. If the particles are moving relative to the ADCP profiler, the frequency of the scattered sound waves will be different from the frequency of the emitted waves. This frequency shift, the Doppler shift, is directly related to the velocity of the particles and thus the water current in the direction of the sound beam.

ADCPs normally operate with a number of acoustic beams, normally four or more, oriented in different directions. The measurement of Doppler shifts from each beam allows the ADCP flow meter to calculate three-dimensional velocity components of the water current. Such data is further processed to give a profile of the current velocity at different depths right from the surface down to some depth-a limit depending upon frequency and power of the ADCP meter.

5. What is needed in order to provide high-quality measurement of Ronda coastal currents?

To perform high-quality measurements of coastal currents in Ronda, the ADCP equipment needs to respond to a number of requirements: above all material reliability is the most important. First of all, it has to be resistant to the aggressive marine medium: salt water, strong currents, and wave action. The size of the ADCP current profiler should be small enough to be easily deployed and not disturb the natural flow of water. A smaller size makes it more applicable for near-shore locations where space is limited.

It should also not have heavy weight to ease the deployment process and minimize the energy to maintain the device in place, particularly in floating or moored installations. The power consumption should be low because many ADCP deployments are found to be very remote or powered by batteries. With low power consumption, it allows such a device to operate for quite a longer period without frequent replacement or recharging of its batteries.

Cost-effectiveness is also essential, particularly for large-scale measurements. A low-cost ADCP enables more widespread deployment, improving the spatial and temporal coverage of the current measurements.

Material-wise, the casing of the ADCP is preferably made of titanium alloy. The reason is that titanium alloy has a very excellent resistance to corrosion; it is able to resist the corrosive action of salt water for a long period of time without significant deterioration. Besides, it is strong yet light and meets both requirements of strength and light weight for ADCPs.

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

Based on Usage

• Ship-borne ADCP: Useful in large-scale surveys of coastal currents where a wide area needs to be covered. While the ship is in movement, the ADCP can continuously measure the currents along the ship's track.
• Bottom-mounted ADCP: Also referred to as a moored ADCP, which is kept on the seafloor. This is used to measure the flow of current in one fixed position over a very long period.
• Buoy-mounted ADCP: It is attached to a buoy and is used in areas where a fixed platform is required but with more mobility than a bottom-mounted device. It can be used to monitor the surface and near-surface currents in a particular area.

Based on Frequency

• The 600kHz frequency ADCP will suffice for waters with less than 70m depth. The higher the frequency, the better it will be to measure currents in relatively shallow waters, since it will be able to give a much higher resolution.
• A 300kHz ADCP would be suitable for waters with approximately 110m depth, giving a very good balance between resolution and depth penetration.
• In water depths up to 1000m, a 75kHz ADCP is generally preferred. The lower the frequency, the deeper it will penetrate through the water column, but it will have reduced resolution.

For such a device, there are several famous brands on the market: Teledyne RDI, Nortek, and Sontek. However, if you need high quality but at a reasonable price, you can consider a Chinese brand: China Sonar PandaADCP. The material is made all of titanium alloy, which will guarantee it to be best in durability in the sea. With its extraordinary cost-performance ratio, it is going to be an excellent solution for measurement of Ronda coastal currents. You can learn more from their website: https://china-sonar.com/.

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