How to Measure the Coastal Currents of Toyama?

1. Where is Toyama?

Toyama is a prefecture located on the Sea of Japan side of Honshu. The city of Toyama is a coastal city, with beautiful scenery, including the Tateyama Kurobe Alpine Route and its rich fishing grounds.

Fishing, manufacturing, and tourism support the local economy. The Sea of Japan off Toyama is a cold-water sea, which sustains catches of cod, squid, and many varieties of shellfish. There are large areas of seaweed beds.

2. What are the conditions of the coastal currents off Toyama?

Various factors influence the coastal currents around Toyama. First, there is the influence of the Tsushima Current. This warm current branching from the Kuroshio Current brings in not only warm water but also nutrients affecting the temperature and distribution of marine life.

Tidal currents are also significant. The Sea of Japan has a high tidal range, and the rise and fall of the tides create complex current patterns. The shape of the coastline and the underwater topography play a crucial role. The presence of bays, headlands, and underwater ridges can cause the currents to change direction and speed. Additionally, the wind patterns, especially the seasonal winds that blow across the Sea of Japan, can drive surface currents and affect the mixing of different water layers.

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

The method of surface drifting buoy release to observe the current of water can be done on the water surface. Buoy motion is followed for a length of time by GPS or another tracking system. However, the procedure has its drawbacks: it presents only the characteristic of current on the water surface and can be covered by wind and waves. For instance, in the case of a strong wind blowing on the buoy in a direction different from the actual current, there is a deviation in the measurement of direction and speed of the current.

It applies from measuring, basically, the current by a series of instruments lowered into the water from an anchored boat: this allows for more refined depth-wise measurements but introduces limitations into the measurement. Because an anchored boat has a fixed position and can only cover a fixed amount of distance, it may not satisfactorily represent all varieties a large coastal area can impose into flow varieties.

The method of the ADCP current meter, therefore, has proved to be an advanced and much more efficient method in measuring the currents of the coastal area. The ADCPs emit an acoustic signal into the water and then measure the Doppler shift of the reflected signal to compute the velocity of the water at various depths, thus yielding a more detailed profile of the current from surface to seabed. They are less affected by surface disturbances and are able to run continuously over longer periods with greater accuracy of the current structure.

4. How do the ADCPs using the Doppler Principle Work?

The working of ADCPs is based on the Doppler principle. They transmit high-frequency acoustic pulses into the water. In cases when these pulses come across moving water particles, the frequency of the reflected pulses changes. When the water particles are moving toward the ADCP current profiler, the frequency of the reflected signal is higher than the emitted one; if they are moving away, it is lower.

The ADCP flow meter has multiple transducers that send and receive signals at different angles. By analyzing the Doppler shifts from different directions and at different depths, the device can calculate the three-dimensional velocity of the water. This means it can determine the horizontal and vertical components of the velocity, providing a detailed understanding of the current's structure and behavior.

5. What is required for good quality measurement of Toyama coastal currents?

For high-quality measurement of the coastal currents near Toyama, the equipment should have reliable materials. Given the marine environment, with saltwater, potential exposure to storms, and the influence of tides and ocean currents, a durable casing is a must. The size of the equipment should be as small as possible for its deployment and retrieval, especially in regard to the complex coastal landscape with bays and headlands.

A lightweight design is preferred because it makes the equipment more manageable during installation and maintenance. Low power consumption is essential for long-term and autonomous operation. Cost-effectiveness is also important to enable large-scale measurements.

The casing of ADCPs is preferably made of titanium alloy. Titanium alloy has excellent corrosion resistance, which is important in withstanding the corrosive nature of seawater. It is strong and durable to stand the pressure of the water at different depths. Its lightweight nature makes it more convenient for various deployment methods.

6. How to Choose the right equipment for current measurement?

When selecting current measurement equipment around Toyama, a preliminary decision based on the purpose is important. In case a vessel is measuring currents in order to navigate or conduct short-term research, it shall be equipped with a ship mounted ADCP, which will inform real - time current details during the voyage.

In cases where measurements would be made close to the seafloor, like in investigations into sediment transport or benthic ecology, a bottom-mounted ADCP is an excellent option. It gives information about the near-bottom current. If coastal current monitoring should be realized long-term and wide-area, then the buoy-type ADCP will be the best means.

Regarding the frequency of ADCPs, for water depths up to 70m, a 600kHz ADCP is a good choice. For depths up to 110m, a 300kHz ADCP is more appropriate. And for deeper waters that might be found near Toyama, such as areas with a depth over 1000m, a 75kHz ADCP is recommended.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all-titanium alloy material and offers an excellent cost-performance ratio. You can find more information on their website: https://china-sonar.com/.

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