How are we going to measure the coastal currents of Lloret de Mar?

1. Where is Lloret de Mar?

Lloret de Mar is a nice-looking coastal town from the province of Girona, Catalonia, Spain. The town is along Costa Brava-a stretch of the Mediterranean coastline famous for being ruggedly beautiful and having crystal clear waters.

It is geographically between mountains and sea. The town is backed by the lush greenery of the Catalan coastal range that provides a magnificent backdrop to it and, at the same time, moderates the climate. It has a typical Mediterranean climate with warm, dry summers and mild winters. Long stretches of sandy beaches in Lloret de Mar are its major attractions, extending for many kilometers and offer several water-based activities.

Because of the crystal-clear waters and good conditions found around Lloret de Mar, so much sea life thrives. The tourism found in this town has lots of hotels, restaurants, and bars. In every respect, there is a presence of the Catalan and the modern beach town culture. Lloret de Mar is a municipality whose people are traditionally linked to the sea, since fishing and maritime trade were until recently an important economic activity of their inhabitants before the rise of tourism-related activities linked with the sea.

2. What is the situation of the coastal currents near Lloret de Mar?

Influence of the Mediterranean Circulation

The coastal currents around Lloret de Mar are influenced by the general circulation of the Mediterranean Sea. The general direction and speed of the water flow is determined by the Western Mediterranean Gyre. Thermohaline circulation, due to differences in temperature and salinity, also plays a role in local currents. It was understood that this local-scale exchange at the Strait of Gibraltar is fundamental for the larger-scale Mediterranean circulation, impacting the coastal currents indirectly as well.

Wind - Driven Currents

The local winds influence coastal currents immensely. This very strong northerly wind-mMeteorology named Tramontana is representative of the region. This could be the case when the Tramontana blows, pushing the surface waters to create currents that alter the normal flow patterns. The wind-driven currents can therefore be quite forceful and, in some instances, lead to upwelling. Upwelling is a process whereby deeper, nutrient-rich waters are brought to the surface, increasing the productivity of the marine ecosystem and thus affecting the distribution of fish and other marine organisms.

Tidal Currents

The tidal forces also play a part in the coastal current situation near Lloret de Mar. Though the tidal ranges in the Mediterranean Sea are relatively small, tides may somehow interact with the coastline topography. The shape of the bays and inlets in this area can amplify the tidal currents. Particularly, narrow channels and areas close to river mouths may experience stronger tidal-driven currents.

3. How to Observe the Coastal Water Flow of Lloret de Mar?

Surface Drifting Buoy Method

The surface drifting buoy method is one of the oldest ways to measure the flow at the surface. They are designed to float on the surface of the water and travel with currents. These buoys can normally be fitted out with GPS or other position-following devices to record positions over time. By analyzing the displacement of the buoys, one can determine the direction and speed of the surface currents. This method does have its limitations. The buoys may be tossed around by winds and waves, so their movement at any particular time may not represent the true current direction and speed. If the weather is windy, the effect of the wind on the buoy's movement can be considerable.

Moored Ship Method

In the moored ship method, the ship is anchored at a certain point in water near the Lloret de Mar shore. It employs current meters and all similar instruments on board that record the flow of water at higher as well as lower levels. It provides a continuous record of currents at one point. This is helpful for providing all the detailed data about the vertical structure of currents. However, it is a costly and time-consuming procedure. Maintaining a ship at a station requires the expenditure of the crew that operates it, the fuel used in it, along with others. The ship itself will cause interference with the flow of the current in that region.

ADCP Method

Acoustic Doppler Current Profiler (ADCP) is more advanced and superior. The ADCPs transmit acoustic signals into the water. These signals reflect off particles in the water, such as plankton, sediment, or even bubbles. By analyzing the frequency shift of the reflected signals-the Doppler shift-the velocity of the water can be determined for a range of water depths. Current velocity profiles across a vertical can be provided by an ADCP, which offers much more information on the current structure than surface-measurement methods. They can be deployed from ships, attached to buoys, or placed on the seabed depending on the measurement requirements.

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

ADCPs work on the principle of the Doppler effect. An ADCP sends out an acoustic signal into the water; the signal travels through the water column. As this signal hits particles moving with the water-the water is in motion-the frequency of the reflected signal changes.

If the particles are moving towards the ADCP, then the frequency of the reflected signal is higher than the original emitted frequency-a positive Doppler shift. If the particles are moving away from the ADCP, then the frequency of the reflected signal is lower-a negative Doppler shift. This frequency change is measured by the ADCP, which calculates the velocity of the water using the known speed of sound in water; the latter depends on such factors as water temperature, salinity, and pressure.

Most ADCPs are fitted with several transducers that measure the velocity components in different directions. By combining these, one can calculate the three-dimensional velocity of the water flow at any depth. In this way, the current patterns around the near-coastal zone of Lloret de Mar will be mapped with a fine resolution.

5. What is required to measure the currents along the coastal area of Lloret de Mar?

Equipment Reliability

Any measuring to be done near Lloret de Mar should be of high quality, requiring the equipment also to be reliable. The marine environment is so unfriendly: saltwater corrosion, strong currents, and wave action can easily destroy test equipment. This means that devices like ADCPs should be able to function within these conditions over time. Once the equipment starts malfunctioning or degrading in performance, the collected data might also turn faulty and thus lead to poor interpretation of the current dynamics.

Small in Size, Light in Weight, and Low in Power Consumption

The instrument of measurement should be small as well as light. For example, a small and lightweight ADCP is easier to deploy whether on a small boat, a buoy, or even at the bottom of the ocean. It will also interfere less with the natural flow of currents. Low power consumption is important, particularly for long-term monitoring. In the marine environment, power sources can be limited, so a device that uses less power can operate for longer without the need for frequent battery replacements or a large power supply.

Low Cost

It means that the price should be low for the equipment in order to perform large-scale measurements. This can be done by deploying several devices along the Lloret de Mar coastline in order to obtain more valuable information about the current patterns. If the cost is higher, then not many deployments may be possible and data collected may not be complete.

Material for Casing

The casing of the equipment, such as an ADCP, is preferably made from a material like titanium alloy. Titanium alloy has excellent corrosion resistance, which is vital for long-term operation in the saltwater environment near Lloret de Mar. It is also relatively lightweight and of high strength, thus enabling the equipment to bear the mechanical stresses of the marine environment, such as the impact of waves and currents.

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

Based on Usage

• Ship-borne ADCP: It is installed on a ship and therefore suitable for making measurements over a large area as the ship moves. In this regard, it can be useful in mapping the overall current patterns along the Lloret de Mar coast. For instance, if one intends to study the general circulation in a large section of the coastal waters, then a ship-borne ADCP can cover that wide area.
• Bottom-mounted ADCP: Also known as a moored ADCP, it is placed on the seabed. It is ideal for long-term, continuous monitoring of the currents at that one point. If you want to know the long-term trends and variations in the currents near a certain point on the coast, then a bottom-mounted ADCP is what you need.
• Buoy-mounted ADCP: It is attached with a floating buoy and drifts with the surface currents. It provides information about the current pattern in the surface layer. It is mainly used for monitoring of shorter-term or more flexible type, specially in locations where the access by ship is difficult or when the data about the surface current is highly valued.

Based on Frequency

• 600kHz ADCP: This frequency is suitable for waters of less than 70 m depth. For the areas in front of the littoral to Lloret de Mar, especially in bays and near the coast, a 600kHz ADCP will adequately measure the currents.
• 300kHz ADCP: It is a device designed for waters with depths of about 110m. In areas where the coastal waters have a moderate depth, a 300kHz ADCP can offer a good balance between measurement range and resolution of the current data.
• 75kHz ADCP: In very deep waters of up to 1000m, this would be suitable. Still, over the deeper parts of the Mediterranean Sea close to Lloret de Mar, a 75kHz ADCP would therefore also be highly appropriate for measuring currents at much greater depths.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. For a cost - effective and high - quality option, the Chinese brand China Sonar PandaADCP is recommended. It's made of titanium alloy and offers excellent reliability and performance at an affordable price. 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.