How then will we measure the current off the coasts of Palawan?

1. Where is Palawan?

Palawan is an idyllic, elongated island province of the Philippines, extending southwest from Mindoro and northeast of Borneo. It is known for its pristine beauty and is still referred to as the "Last Frontier."

Geographically, the place is enclosed to the west by the South China Sea and to the east by the Sulu Sea. The beaches along the coastline of the island vary from an enchanting wonderland of white sand to limestone cliffs and concealed lagoons. The waters of Palawan are every color of the spectrum, from the brightest turquoise of shallow reefs to the dark blue of the open sea. The Palawan Underground River is a UNESCO World Heritage Site and evidence of the very peculiar karst topography of the area.

Diverse ecosystems filled this island. Mangrove forests are normally the outline of many of the coastlines, protecting shorelines from erosion and serving as a vital nursery for fish. Fringing most of the coastline, coral reefs are among the most biodiverse on the planet, inhabited by an array of marine life, including colorful corals, tropical fish, and sea turtles.

It is home to a number of ethnic peoples, the Tagbanwa and the Palawano. These respective indigenous peoples have a mix of culture that is inextricably linked with all the resources of the island. The local economy is supported by fishing, tourism, and agriculture. Indeed, the laid - back island lifestyle is a major tourist draw for beach resorts, island hopping opportunities, and exposure to the still unspoiled wilderness.

2. How are the coastal currents around Palawan?

Various factors influence these coastal currents in Palawan. For one, tides determine the flow of these currents. Semi-diurnal tides cause predictable tides to ebb and flow into this particular body of water. During high tide, the sea brims over and brings with it the nutrient-rich sediments inland onto the shoreline, nourishing the various ecosystems of the coastline. Conversely, when it is low tide, waters recede, which in turn uncovers part of the seabed and alters characteristics of the currents.

The great influence is also introduced by monsoon winds. The southwest monsoon, locally known as Habagat, and the northeast monsoon, known as Amihan, introduce winds of opposite directions, which influence the coastal currents. Whereas Habagat can push the currents in one direction because of prevailing winds, often carrying warmer waters from the South China Sea, Amihan winds are able to reverse or change this flow and sometimes lead to upwelling events. Because the winds drive surface waters away, deeper waters rich in nutrients can rise to the surface. Productivity in the marine ecosystem may then be enhanced.

The seabed topography is another consideration in the case of Palawan. The occurrence of coral reefs, seamounts, and channels, which may bypass and accelerate the current. The complicated form of the coastline, with all its bays and coves, influences the currents through their complicated shapes. For instance, a current may be deflected sideways around a headland, creating areas of stronger flow on one side and calmer waters on the other. In addition, the inflow of fresh water from minor rivers and streams can influence the salinity and hence density of coastal waters and thereby affect the currents.

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

For the precise measurement of the coastal water currents in Palawan, determination of its velocities and flow rate is necessary. As the methods conventionally used for current measurement have drawbacks, ADCP can be more advanced and convenient.

3.1 How do ADCPs using the principle of the Doppler work?

The Acoustic Doppler Current Profiler(ADCP) work on the principle of the Doppler. They pr​oduce acoustic signals into the water column. These signals interface with particles such as plankton and sediment that are in suspension within the water. As the water current moves these particles, the frequency of the reflected acoustic signal changes relative to the originally produced signal. This Doppler shift has a direct relationship with the velocity of the particles and therefore with the velocity of the water current.

Commonly, an ADCP current profiler emits several beams of acoustic signals at different angles. By this method, they are able to calculate the velocity of the water current in three-dimensional space. This is because, from the multi-beam Doppler shifts, the ADCP current meter is able to calculate in great detail the actual profile of current flow conditions both horizontally and vertically within the column of water. Subsequently, data can be used to calculate the flow rate of the coastal currents, which is an essential constituent in many applications: marine navigation, coastal engineering, and environmental studies, among others.

3.2 What is required to have high - quality measurement of Palawan coastal currents?

High-quality measurement of the coastal currents near Palawan necessitates that a number of equipment requirements be met. The material constitution of the ADCP current profiler is expected to be reliable to endure such a harsh marine environment: when exposed to saltwater, under great pressure at different depths, and against impacts of floating debris.

Another important aspect is the size and weight of the ADCP flow meter. The smaller and lighter a device, the easier it is to deploy and handle. For example, if it is to be installed on a boat or buoy, a lighter ADCP meter would be more practical. Low power consumption is equally crucial, especially for long-term measurement purposes. This will enable the device to run continuously without frequent battery replacement or an enormous power supply.

Other key factors include cost-effectiveness. The ADCP price should be reasonable to accommodate the measurements that are normally done on a large scale. The casing of the ADCP profiler is made from the alloy of Titanium. It has excellent corrosion resistance suitable for marine conditions that easily corrode metals, especially seawater. It is also strong and durable, capable of withstanding water pressures and stresses underwater. Its relatively low density is helpful in maintaining the overall weight of the ADCP relatively low, a plus for ease of deployment.

3.3 How to Choose the right equipment for current measurement?

In identifying the right equipment to be used for measuring the coastal currents of Palawan, several aspects must be considered.

According to the deployment method, there are several types of ADCPs. Ship-borne ADCP is installed on a ship and may be used in those surveys where the ship can navigate along the coast. With this type of ADCP, the currents along the coast can be viewed over a large area and in a wide range.

The bottom-mounted ADCP, or sit-on-bottom ADCP, is laid on the seabed and continuously monitors the currents that pass over it. It is ideal in monitoring specific locations like near a coast structure or an area of particular interest from the point of view of marine ecological studies.

The buoy-mounted ADCP can be attached to a buoy and float freely in the water while measuring the currents surrounding it. This is advantageous for sites that are inaccessible by ship or where continuous monitoring from a fixed position in the water is required, like in open waters near the coast of Palawan.

Apart from the deployment method, the other important consideration is the frequency of the ADCP. For water depths of up to 70 meters, a 600 kHz ADCP would be workable. This frequency offers high-resolution measurements in shallower waters. In water with depths up to 110 meters, a 300 kHz ADCP can be used. It offers a balance between resolution and depth of penetration. For the much deeper waters up to 1000 meters, there is designed a 75 kHz. ADCP for such depth. It is capable of penetrating more into the water column for the measurement of currents.

There are well - known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with good quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, which not only ensures its durability and resistance to the marine environment but also provides an incredible cost - performance ratio. You can find more information about this product on their website: https://china-Sonar.com/.

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