How can we measure the coastal currents of Baguio?

1. Location of Baguio

Baguio is a city in the Philippines but is not a coastal city. It is situated in the Cordillera Administrative Region, about 250 kilometers north of Manila.

Geographically, it outcrops in the mountain at an altitude of about 1,500 meters above sea level. Because of its geography, the city enjoys a cool climate, quite different from the hot tropics of its lowlands. It is also bounded mostly by pine forests and mountains with beautiful scenery and plenty of outdoor activities like hiking and mountain climbing.

The culture of Baguio City is basically indigenous, peopled by various ethnic groups. The Igorot predominant amongst the rest. It is a tourist destination, especially during summer where people from lowland areas go up to spend their vacation. It is also a center for education, housing several universities and colleges.

It is not a coastal city and, therefore, does not contain typical features of a coastal city such as adjacent bays and tidal zones. Its physical setting in the mountain may contribute to influencing the hydrologic cycle and water flow in lower-order river systems that eventually empty into the coast.

2. What about the situation of the coastal currents near Baguio, even though it's not coastal?

Being inland and mountainous, Baguio does not have direct currents from the coast. But of course, the water from the rains and rivers in the area find their ways to the sea. As a matter of fact, rainfall, topography such as steep valleys that may cause rapid flow, and soil and vegetation cover influencing infiltration and runoff are just a few of the many factors that affect streams and rivers here in the mountainous Cordillera Region.

By the time it reaches the coast, after passing through various river systems, the currents in those places are influenced by tides, winds, and coastline shape. The gravitational pull of the moon and the sun drives tidal currents. Currents which are wind-driven happen when winds push the surface waters. The configuration of the ocean floor and the contour of the coastline, in the form of bays, headlands, and estuaries, can also deflect and alter the coastal current.

3. How to observe the coastal water flow of the areas affected by Baguio's water runoff?

As far as the area where the water coming from Baguio and its surrounding areas reaches the coast, coastal currents do have their own characteristics in terms of velocity and flow rate. Velocity is slow in sheltered coves to fast at areas where the water constricts, such as at the entrances of small inlets, at areas with strong winds, and at areas where tides affect the area. The flow rate is basically measured by the volume of water passing through a given area per unit time.

These coastal currents can effectively be measured by an instrument known as Acoustic Doppler Current Profilers. ADCP current meter is those which can give quite accurate and detailed data regarding the water flow at higher depths.

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

The Acoustic Doppler Current Profiler(ADCP) work on the principle of the Doppler effect. They send out acoustic signals into the water. The moving particles in the water-like sediment, plankton, and other small organisms-interact with these signals. When the acoustic waves bounce back from such moving particles, the frequency of the reflected waves changes.

The change in frequency is, hence, directly proportional to the velocity of the moving particles and, therefore, the velocity of the water. Since a number of acoustic beams are emitted at different angles, an ADCP current profiler is capable of measuring three-dimensional velocities of the water, including horizontal and vertical components. Data collected undergo processing for useful information on the coastal currents.

3.2 What is required for excellent measurement of the coastal currents associated with Baguio runoff?

In the measurement of the coastal currents associated with runoff whose origin is considered to be in Baguio, for instance, the equipment used has to be made from sufficiently reliable material. The equipment must not corrode due to saltwater or due to humidity and large temperature fluctuations.

It must be compact, light with low power consumption, and at a low cost for extensive measurements. For ADCP doppler, a Titanium alloy casing is preferred. The corrosion resistance of a Titanium alloy is very good, which is an important prerequisite in the salt-water environment. It should be strong, durable to resist mechanical stresses related to the marine environment. Its relatively low density will tend to minimize the overall weight of equipment, and it has good thermal stability, hence suitable for the variable temperature conditions in the sea.

3.3 How to Choose the right equipment for current measurement?

While choosing current measurement equipment for the areas affected by Baguio's runoff, the deployment method has to be considered. There are different types of ADCP flow meter for different applications.

A ship-mounted ADCP would suit ship-based measurements, which can measure the current in motion as the ship moves on water.

If the measurement needs to be done from the seabed, then it would be right to have a bottom-mounted ADCP meter. The instrument is placed on the seabed and measures all current that passes over it.

An ADCP buoy-mounted is the proper one for measurements with a floating platform, like a buoy. It measures currents around the buoy.

In regard to the choice of frequency, for depths up to 70m, a frequency of 600kHz allows for high-resolution measurements with an ADCP profiler. For between 70 and 110 meters, one will have to use a 300kHz ADCP while at 1000m depth, the 75kHz ADCP will be considered due to its sufficient depth penetration, which will provide correct measurements for the currents.

Among the ADCP brands, well - known ones include Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with excellent quality, the China Sonar PandaADCP is a good choice. It is made of all - titanium alloy and offers an excellent price - performance ratio. You can visit https://china-sonar.com/ for more details.

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