How do we measure the coastal currents of Santander?

1. Where is Santander?

Santander is a great city on the northern coast of Spain in the self-government community of Cantabria. The city is located smoothly upon the shores of the Bay of Biscay. All its privileged situations have been very important for the historical, cultural, and economic development of this city.

It is one of those cities that integrates into its entity all the charms of a rich history, mixed with the attraction of modernity. It first began during ancient times with the presence of early human settlements. Throughout the centuries, Santander has been influenced by all kinds of cultures, from the Roman culture, which can still be seen in remains like the archaeological site of Baelo Claudia, to the present time. These manifestations of its rich heritage are visibly expressed in the architecture of Santander, a harmonious mix of medieval, Renaissance, and modern-day styles. The Palacio de la Magdalena is a very beautiful palace-like structure that has become an iconic symbol of Santander, commanding a view of breathtaking beauty over the bay.

Santander boasts a rich cultural and artistic heritage. Throughout the year, the city hosts a number of festivals and events that attract people from all over the world. It also has various museums, art galleries, and theaters that showcase a wide range of artistic expressions. Apart from that, Santander is a famous tourist destination because of its beautiful beaches; one of them is Playa de la Concha, which is considered one of the most beautiful urban beaches in Europe. The bay itself is an important part of the local ecosystem, supporting everything from fish and dolphins to seabirds.

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

The numerous influences responsible for the determination of the coastal current pattern around Santander are too numerous to list, but a priori, tidal forces should be taken into consideration. Gravitational pull of the moon and the sun causes ebbs and flows of the tides at the Bay of Biscay. Upon high tide, water surges into the bay and develops into strong incoming currents able to significantly affect the waters around Santander. In contrast, at low tide, the water moves back into the ocean, creating outgoing currents. The strength and speed of tidal currents also change with the various phases of the moon; during spring tides, stronger currents are seen compared to neap tides.

This is in addition to the contribution of wind patterns. Wind from the Atlantic Ocean can be the prevalent factor that would determine the pattern in the surface current. The common westerly winds in the region can push water toward the coast, which would intensify the incoming currents and affect the distribution of heat, nutrients, and marine organisms. Easterly winds would cause the water to move away from the shore. The strength and direction of the wind can also change seasonally, leading to variations in the coastal current patterns throughout the year. More energetic currents may form if stronger winds occurred during winter periods, for example.

Another main factor is the bottom bathymetry from the Santander Sea. The shapes and depth would choke or widen the flow of water. There are submarine canyons and ridges with shallow banks which can affect both direction and speed of currents involved here. While a narrow channel between two headlands can accelerate the current, a broad flat seabed area can result in a more dispersed flow. In addition, freshwater input from local rivers that empty into the bay modifies the density of the seawater, and thus generates density-driven currents. Such density differences can drive the movement of water masses vertically and horizontally, further complicating the current patterns.

3. How to Observe the Coastal Water Flow of Santander?

Surface Drift Buoy Method

One of the simpler methods of observing the coastal water flow is by using the surface drift buoy. A buoy is designed to float on the surface of the water and travel with the currents. For tracking purposes, these are prepared with locating appliances like GPS transmitters that send out signals at periodic intervals. These buoys, while a good estimator for the currents when their movements over time are tracked, record only the movements of the upper few meters of the water column, and there might be interference in such records by other surface-level phenomena such as wind-driven waves that deviate these buoys from a path of pure current. This means that actual current conditions can only be indirectly inferred at the deeper levels. It also means the buoys are subject to local winds that can carry them in certain directions independent of the currents of interest.

Moored Ship Method

The moored ship method uses a ship, moored at one location in an area of interest. Currents are measured from the boat using instruments attached to it, usually mechanical current meters. The mechanical current meters usually consist of a propeller-like device which rotates due to the flow of water around it. The speed of the rotation is converted to a measure of current velocity. Although the method can be very accurate for any given point, there are many disadvantages to it. The current would also be interfered with by the presence of the ship, impeding a natural flow, especially in shallow waters. Turbulence could be generated by the hull and anchor of the ship, which may affect the accuracy of the measurements. Besides, the spatial coverage is limited to the immediate vicinity of the moored ship, which does not allow a view of large-scale current patterns. Besides, weather conditions may interfere with the ship's ability to maintain a fixed position for good measurement.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter method has proved to be one of the modern and more flexible methods of measurement of coastal currents. ADCPs can measure simultaneously the velocity of water at multiple depths in the water column. They work by sending acoustic signals into the water. These signals are reflected from small particles that may be suspended in the water, like plankton, sediment, or even air bubbles. An ADCP uses the Doppler shift of these reflected signals to calculate the velocity of the water at an array of depths. With this method, high-resolution data is attained over a reasonably large area. It can be deployed from different platforms: ships, buoys, or fixed moorings, each useful for various measurement scenarios. The ADCP offers a detailed profile in the vertical dimension of the structure of currents, thus showing to scientists complex surface and subsurface current interactions. The three-dimensional water flow velocity may also be measured by an ADCP current profiler for a far more complete impression of the dynamics of the currents.

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

An ADCP flow meter works on the principle of the Doppler. When an ADCP sends out an acoustic wave through the water medium, this wave hits small particles in the water current, after which it comes back to its origin with a frequency different than that of the originally emitted wave. This frequency shift, often referred to as the Doppler shift, is linearly proportional to the velocity of the particles, and hence to the water velocity. Most ADCPs use multiple acoustic beams, usually four or more, oriented in different directions. The ADCP can calculate the three-dimensional velocity of the water flow by determining the Doppler shift in each of these beams. For example, one beam is pointed slightly downwards, another upwards, and others horizontally; the combined data from such beams can effectively determine the vertical and horizontal components of the current velocity. Being able to measure the full vector of the current velocity is a big plus for ADCPs in order to get an even more complete understanding of the very complex flow dynamics in coastal waters. It can also measure water depth by timing how long it takes acoustic pulses to travel from the transducer to the bottom and back. That provides depth that will be used in understanding the vertical structure of the currents, interaction with the seabed.

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

Equipment Reliability

For the measurement of the currents around the coast of Santander with high quality, the most important aspect is the reliability of the equipment. The marine environment is pretty harsh with high salinity, strong waves, and variable weather conditions. Therefore, ADCPs should be constructed from materials that are resistant to such adversities. The components should be resistant to corrosion, and electronics must be well-protected from water ingress. A reliable ADCP meter would mean that the data collected would be accurate and consistent in long-term deployments; any malfunction of the equipment or inaccuracy can lead to incorrect data that might misinterpret the coastal current patterns and their implications for the local ecosystem and human activities. The equipment should also be able to resist mechanical stresses, such as those caused by wave impacts and water pressure.

Size, Weight, and Power Consumption

The ADCP should be compact in size. A small device is easier to deploy in different areas, which is particularly important in relatively shallow waters or in areas where access is limited. Its interference with natural flow is also less. This might be the factor under consideration in narrow inlets or along the shorelines of Santander, where a bulky device cannot be practical. The ADCP should be light in weight, particularly for applications where it would be deployed from floating platforms or small vessels. This reduces the load on the platform and makes installation and retrieval easier. Low power consumption is another critical factor: in many cases, ADCPs may have power supplied by batteries or renewable energy sources, such as solar panels. A device with low power requirements can operate for extended periods without the need for frequent recharging or refueling, thus ensuring continuous data collection. This is of particular importance in remote coastal areas near Santander where access to power sources may be limited.

Cost-effectiveness

Cost-effectiveness is a key consideration, especially when large-scale measurements are required. Several ADCPs would have to be deployed at different locations in order to fully understand the coastal currents around Santander. Only a cost-effective ADCP can make such large-scale studies viable without making the study prohibitively expensive. High-priced equipment will limit the number of devices that can be deployed; hence, incomplete data collection. It is therefore important that an optimum cost-performance balance should be considered when trying to measure the coastal currents as accurately as possible. Cost-effectiveness can also be included in the consideration of maintenance costs and the cost of data acquisition and processing.

ADCP Casing

The casing of the ADCP is preferably of titanium alloy. The immediate advantages of the titanium alloy are:. It consists of excellent resistance to corrosion, which is necessary for long-term exposure in the saline environment of the coastal waters of Santander. The strength-to-weight ratio is high in the titanium alloy; thus, the casing will be able to bear the mechanical stresses brought about by a marine environmental load, such as wave impact and water pressure, but still remain light in weight. In addition, titanium alloy is biocompatible; therefore, it will have little impact on the marine habitat. This is important in light of Santander's coastal waters hosting a number of various types of marine species; any material that may be deployed in measurement tools should therefore be benign to the environment. Its biocompatibility decreases the chance of fouling and its negative effect on ADCP profiler performance after a long period of exposure.

6. How to Select Appropriate Equipment for Current Measurement?

According to Application

• Ship-borne ADCP: This type of ADCP is installed in a moving ship. This type of ADCP is ideal for large-scale surveys of coastal currents over a wide area. While the ship is traveling across different regions of the Bay of Biscay near Santander, the ADCP can record the currents continuously along the path of the ship. This provides a broad-scale view of the current distribution, which is useful for large-scale oceanographic processes and applications such as shipping route planning. Ship-borne ADCPs can cover large distances in short periods of time, thus enabling extensive current patterns to be mapped in relatively short times. They are also usable for the study of spatial variability in the currents, an important insight in understanding the nature and relation between the current and diverse sections of a coastline.
• Bottom-mounted ADCP: Also referred to as the moored or bottom-tripod ADCP, which sits on the seabed, this works when longer, fixed-site measurements are called for. If deployed to rest stationary on the seafloor, it could offer continuous information about currents on a particular site, and consequently, studies about the nature of the currents, the change of local patterns, and seasonal changes would affect the ecosystem at the benthic or sea floor. Bottom-mounted ADCPs provide further insight into the interaction between currents and the seafloor that can relate to sediment transport and distribution of benthic organisms. They can also be used to monitor the changes in current patterns over long periods, which is important in the detection of any long-term trends or impacts from human activities.
• Floating-buoy ADCP: These ADCPs are attached to a floating buoy. They can either be stationary buoys anchored in place or drifting buoys that move with the currents. Floating buoy ADCPs would be useful means of monitoring movements of water masses and studying interaction between surface and subsurface currents, not to mention providing in-situ real-time data regarding current condition within a particular area. They also can be deployed at locations where a ship-based or bottom-mounted measurement is hardly feasible, say in shallow lagoons with very strong tidal currents. Floating - buoy ADCPs can also be used in the study of the temporal variability of the currents because they provide continuous data with time.

Based on Frequency

Frequency in ADCP depends on water depth in use.

• A 600kHz ADCP is well suited to measure in waters to approximately 70m. Thus, the higher frequency allows for high-resolution measurements of the current velocity in shallow waters, as in estuaries, near-shore areas, and the shallower parts of the Bay of Biscay near Santander. In these areas, the more detailed information provided by the 600 kHz ADCP can help in understanding the complex flow patterns influenced by the coastline and local bathymetry. The high-resolution data can also be used to study the small-scale variations in the currents, which can be important for understanding the behavior of marine organisms in these areas.
• A 300kHz ADCP is appropriate for water depths of around 110m. It provides a good balance between depth penetration and vertical resolution and therefore is often suitable for most of the coastal applications, especially when the water depth is not very shallow or very deep. It would give good information about the present structure of currents when the depth is not very shallow or deep. These mid-depth currents could be studied with the aid of the 300kHz ADCP, which could possibly be highly useful in learning about nutrient transportation and that of pollutants within the water column.
• A 75kHz ADCP can be installed in deeper waters as high as 1000m. While low frequency can reach further down inside the water column than higher-frequency models, it could also result in lower resolution along the vertical scale. In the deeper parts of the Bay of Biscay near Santander, the 75kHz ADCP can be used to measure the currents at greater depths-a necessity for understanding the overall circulation of the bay. The lower frequency allows a larger coverage area that can be useful in studying the large-scale patterns of the deep-water currents.

The major players for the ADCP are Teledyne RDI, Nortek, and Sontek. But for a cost-effective yet qualitative product for clients, the China Sonar PandaADCP needs to be at the top recommendation. Being wholly of Titanium alloy, this enjoys very good strength while enjoying an appealing price. Its all-titanium construction ensures long-term reliability in the harsh marine environment, while its cost-effectiveness makes it accessible for a wide range of users, from research institutions to small-scale marine monitoring projects. You can find more information about this product at the website: (https://china-sonar.com/). It not only provides reliable equipment but also helps in making current measurement of quality more accessible and cheaply to the scientific community and people involved in coastal management around Santander.

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