How can we measure the coastal currents of Koper

1. Where is Koper?

Koper is an attractive coastal town in southwestern Slovenia, with a coastline to the northern part of the Adriatic Sea. It has been the largest city in Slovenia based on its port and has been strategically positioned at the heart of the Istrian Peninsula. This strategic location has made it a significant hub for trade and cultural exchange throughout history.

Geographically, Koper is situated in a bay that naturally protects it from the open sea. Its coastal area presents a nice balance of rocky outcrops and small, sandy coves. The seabed off Koper is gently sloping, with a mix of sediment and rocky formations that influence the local marine ecosystem. Waters in the Adriatic Sea here are rather clear and temperate, hosting a wide variety of marine life.

Koper is multiculture featured. This municipality has lived its history within a multitude of different civilizations throughout centuries: from Romans to Venetians and Austrians, who left the stamp in their architecture. Representative examples include city walls from antique times, the palaces built in Venetian style, and the Baroque-style church. It constitutes a rich union of tastes among the fresh sea food, pasta, and solid stews-both of the Mediterranean and Central European culinary arts.

2. In what condition are the coastal currents off Koper?

The currents along the coast of Koper are caused by many aspects combined. One major factor in these currents is wind. There is a powerful, cold northeasterly wind called Bora, with very strong gusts at times, which constantly affects the surface currents. Whenever the Bora blows, it may push the surface water towards the shore and thus changes the direction and speed of the coastal currents. In contrast, its opponent, the southerly wind called Jugo, can act oppositely: forcing the water away from the coast.

Again, tidal forces do their part. Though the Adriatic Sea is of a generally small tidal range compared with other seas, it gives rise to regular ebbs and flows. This movement then interacts with local bathymetry. The shallow seabed in general, along with underwater ridges and channels of deeper levels, may lead to divergence or convergence and, even more often, to the change in vertical structure of the currents around Koper.

Another factor is river runoff. In the area of Koper, there are small rivers and streams flowing into the sea. It could change the density structure of the coastal waters by means of freshwater input. The lighter, less dense wastewater floats on top of the surface layer of the heavier, saltier seawater in a type of two-layer flow, and changes in the current might occur, especially in the neighborhood of river mouths.

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

Surface Drifting Buoy Method

Surface drifting buoys are a simple but useful means for observing coastal currents. These buoys are fitted with GPS tracking devices. Once deployed in the water, they are transported by the surface currents. By tracking over time the locations of the buoys from this position, scientists are able to determine direction and speed of the surface -level currents. This method indicates only the flow in the uppermost portion of the water column, usually extending no more than a few meters deep, and may or may not be indicative of the flow at greater depth.

Anchor-moored Ship Method

One of the ways to measure coastal currents is by using an anchor-moored ship. Current meters attached to the hull of the ship at various depths record the speed and direction of the current at each depth as water moves past the ship. This method allows the collection of data from multiple depths and provides insights into the vertical structure of the currents. Nevertheless, it is limited to the area in which the vessel is anchored, and the presence of the vessel itself may disturb the natural current to a certain extent and hence the measurement result.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) represents one of the most sophisticated and handy devices for the measurement of coastal currents in the vicinity of Koper. It can be deployed in several ways: on a ship, fixed to the seabed, or attached to a buoy. ADCPs send out acoustic signals into the water. These signals reflect off suspended particles in the water, such as plankton, sediment, or small bubbles. Since ADCPs measure the Doppler shift of the reflected signals, their independent calculations about the velocity in different layers within the water column can be pretty accurate. Indeed, this methodology allows for the collection of very high-resolution data across a considerable area, helping in the details of the three-dimensional structure of the coastal currents.

4. Working of ADCP using the Principle of Doppler

ADCPs are based on the principle of the Doppler effect. The instrument sends out acoustic signals at a known frequency, and when they return, their frequency will be different due to reflection from the moving particles in the water. If the particles happen to be moving toward the ADCP current meter, the reflected signal frequency increases-higher-frequency shift (blue-shift)-whereas if the particles are moving away, the frequency will have a lower-frequency shift (red-shift).

The frequency shift is measured by the ADCP meter. It calculates the velocity of the water by knowing the original frequency of the emitted signal and the measured frequency of the reflected signal. Signals are emitted at several angles to measure the three-dimensional velocity of the water flow. Besides, the time-of-travel of the acoustic signals to the particles and back can also be used by the ADCP profiler to estimate the depth over which the velocity measurements are being taken.

5. What's needed for high-quality measurement of Koper coastal currents?

Equipment Requirements

• Material Reliability: The casing of the ADCP current profiler has to be fabricated from a material that can operate in the very harsh marine conditions. Titanium alloy is ideal for this. This provides superior resistance to corrosion for long-term functioning in salty water conditions in the Adriatic Sea. Titanium alloy can resist all the effects from saltwater corrosion, mechanical stresses, and also the high pressure at greater depth.
• Small Size and Lightweight: Small size and lightweight are important. A compact and lightweight ADCP is much easier to be deployed: it can easily be installed on everything from a small research vessel or buoy to seabed-mounted applications. Reduced size minimizes the impact of the device on natural water flow and thus provides for more accurate measurements.
• Low Power Consumption: Since most ADCP flow meter deployments could be done with battery power or limited power sources, the power consumption needs to be very low. In such a way, the device would be able to work continuously for a long time without frequent replacement or recharging of the batteries. This is quite important in the case of long-term monitoring of coastal currents.
• Low Cost: To gain information on large-scale currents along the coastal environment of Koper, a relatively low-cost ADCP needs to be applied. Lower costs enable setting up more devices at different sites, which enables more profound insight into the complex current patterns in an area.

6. How to Select Appropriate Equipment for Current Measurement?

According to Use

• Ship-borne ADCP: This type of ADCP is installed on a moving ship. It is ideal for conducting large-scale surveys of the coastal currents. While the ship is sailing through the water, the ADCP can continuously measure the currents at different locations, thus providing a broad-scale view of the current patterns. It is useful for mapping out large areas of the coastal waters around Koper.
• Bottom-mounted ADCPs: These are deployed on the ocean floor. They are ideal for long-term, fixed-point measurements. In being stationary at the ocean bottom, they could record the conditions of the currents over a particular spot for years and seasons, showing the very long-term variability and trends within those coastal currents, such as how the speeds and directions vary with seasons and years.
• Buoy-mounted ADCP: Buoy-mounted ADCPs are attached to floating buoys. They move with the water currents, providing real-time data on the movement of the water masses. This type is useful in studying surface-layer currents and their short-term changes. It can also be used for tracking the movement of water masses in relation to weather events.

Based on Frequency

• The ADCP frequency of choice is dependent on the depth of water to be measured. A 600kHz ADCP is suited for water depths up to about 70m. It gives high-resolution data for shallow-water applications, such as nearshore areas around Koper. With the higher frequency, more detailed measurements can be made in these relatively shallow coastal waters.
• A 300kHz ADCP can be used for water depths of about 110m, which is the best option to use in an area with middle water depth values around Koper. The smaller frequency enables this acoustic signal to penetrate deeper compared to the ADCP of 600kHz into the water column.
• For deeper waters, up to 1000m, a 75kHz ADCP would be more suitable. This is because the lower frequency would allow the acoustic signals to travel greater distances through the water, thus finding application in measuring currents in the deeper parts of the Adriatic Sea near Koper.

Recommended Brands

There are several known ADCP brands on the market. Teledyne RDI, Nortek, and Sontek are among the leading manufacturers. However, for those looking for an economical yet high - quality option, the Chinese brand China Sonar PandaADCP is highly recommended. Made of all - titanium alloy, it offers excellent durability and corrosion resistance. This brand provides an outstanding cost-performance ratio, making it suitable for large-scale coastal current measurements around Koper. 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.