How can we measure the coastal currents of Faro?

1. Where is Faro?

Faro is the administrative centre of the Algarve Region in southern Portugal. Faro is on the southern coast of the Iberian Peninsula, facing the Atlantic Ocean. Actually, it's a coastal town where natural beauty combines well with rich history, therefore becoming a destination for people across the globe.

The city of Faro is nestled within the Ria Formosa, a vast and singular lagoon system separated from the ocean by a chain of barrier islands. The lagoon is a haven for diverse bird species and a variety of marine life, hence an important ecological area. The coastal waters around Faro are relatively shallow near the shore, gradually deepening as they extend further out to sea. The bottom is a mix of sand and silt, with isolated rock outcrops in many places, further adding to diversity on the seafloor.

Faro itself is a city of ancient grace. Its old town is enclosed by walls dating back centuries, with narrow and curving streets lined with whitewash and Moorish arches bright with tile work. The city reflects the great variance in cultures due to its location-a place passed by various civilizations throughout time.

2. What is the condition of the currents off Faro's coast?

Various factors interact on the coastal currents around Faro: tides-the regular rise and fall of the tides push the water in and out of the Ria Formosa lagoon; this gives rise to very complicated current patterns along the coast, with stronger currents often recorded during high and low tide.

The other major influence of the coastal currents is the prevailing winds. The winds which blow from the Atlantic Ocean are capable of pushing the surface waters, thus generating surface currents flowing in the direction of the wind. Other than this, the general circulation patterns of the Atlantic Ocean may intrude into water masses from other regions, which further can alter the temperature, salinity, and flow direction of the local coastal currents.

The seabed topography and shape of coastline around Faro are further cause for the currents. Seabed topography, sandbars, channels, and the entrance to Ria Formosa lagoon may act as reasons for speeding up or slowing down currents, sometimes even changing directions.

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

Surface Drift Buoy Method: In this method, the surface drift buoys are released in the water. These buoys will move with the moving surface currents of water. At the same time, their movement can be tracked by GPS or any other tracking system. After observing the position and travel of the buoys over a certain period of time, the direction and speed of the surface currents can be calculated. This method is only used for the measurement of surface currents and has certain limitations in measuring the currents at depth.

Anchored Ship Method: One of the methods is to use an anchored ship as a platform for current measurement. Instruments are installed on the ship to measure the water flow around it. This will give a more accurate measurement of a particular spot, but its applications are confined to the area near the ship only and it may be interfered with by the after-effects of the ship's wake.

Acoustic Doppler Current Profiler Method: The ADCP current meter is an advanced technique followed for coastal current measurements. It makes use of sound waves in order to find the velocity at different levels. By emitting an acoustic pulse, it analyzes the Doppler shift of the reflected wave and gives an accurate profile from the surface up to a specific depth. It is a more comprehensive method that can give a better understanding of the overall current structure near Faro.

4. How do ADCPs using the Doppler principle work?

ADCPs rely on the principle of the Doppler effect. A known frequency sound is transmitted into the water. If that encounters particles of water in motion, the reflected signal frequency is different. The difference in frequency will relate directly to the speed of the particles of water.

The ADCP current profiler has several transducers that can send and receive signals in different directions. The ADCP flow meter can calculate the velocity components of the water in both the horizontal and vertical directions by measuring the frequency shifts in these different directions. Thus, it is able to build a three-dimensional profile of the current velocities in the water column for detailed information on the flow patterns, including the direction, speed, and shear of the currents.

5. What is required in order to measure the Faro coastal currents of high quality?

It needs to be made from reliable materials to put up with the corrosive seawater and harsh marine environment for high-quality measurement of the coastal currents near Faro. The device should be of small size and lightweight for easy deployment and installation. Low power consumption is also critical for long-term operation without the frequency of battery replacement or issues over a power source. Cost-effectiveness is one of the most desirable factors in executing large-scale measurements.

The casing of the ADCPs could be made of titanium alloy. It is an exceptionally good material, outstanding in corrosion resistance to resist the salty and sometimes harsh conditions of the coastal waters near Faro. A high strength-to-weight ratio in a titanium alloy will make the casing strong enough but relatively light, hence handling and deploying the equipment easier. This will ensure stability and reliability at the marine site.

6. How to Choose the Appropriate Equipment to Measure Currents?

From the Deployment Method

• Ship-borne ADCP: For measuring currents during both the on-course and lying ship, this type can provide its services even from sea coasts also. It enjoys greater flexibility due to covering of wide areas and continuous information provision at greater areas after alteration in the vessel position.
• Bottom-mounted ADCP: Applicable for fixed-point measurements at a specific location on the seabed. It can provide long-term and accurate data about the current conditions at that particular point, which is useful for understanding local current patterns.
• Buoy-mounted ADCP: An ADCP fixed on a buoy can measure the currents near the water surface and transmit them wirelessly. Quite convenient for remote monitoring, and, depending on the buoy's movement, it could cover a big area.

Based on Frequency

Different frequencies are suitable for different water depths. A 600 kHz ADCP is good to go for water depths up to 70 meters, a 300 kHz ADCP does the job for up to 110 meters of depth, while a 75 kHz ADCP works for deeper waters of up to 1000 meters. It enables one to select the most appropriate ADCP based on real water depth in the area around Faro.

Well-known ADCP brands include Teledyne RDI, Nortek, and Sontek. But China Sonar PandaADCP should not be missed. Made of all-titanium alloy material, it can be durable and has an excellent cost-performance ratio. You can visit their website at https://china-sonar.com/ for more information.

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