How do we measure the coastal currents of Machala?

1. Where is Machala?

The largest port city in southwestern Ecuador, Machala, is found on the coast of the Pacific Ocean. Situated near the Gulf of Guayaquil, one of the region's largest gulfs, Machala benefits from a trade and transportation-preferred location. The El Oro province in which Machala resides is famous for its diverse ecosystem, ranging from coastal mangrove to dry forest.

Geographically, the area near Machala is a pretty flat coastal lowland which slope upwards to foothills of Andes Mountains gradually. There are sandy beaches along the coast and estuaries along with outcrops on the rocky seashores. The shores have mangrove swamps along it, and those are the factors maintaining the surrounding in a well-balanced status. These supply nursery for huge fish population, protect the shoreline from erosion, and hold polluting elements in it.

Machala is rich in history. There were people who originally inhabited the region, and their presence can still be felt in local tradition, art, and food. Spanish colonizers arrived in the 16th century and brought with them new agricultural and trading methods. Machala grew into a successful commercial center over time, with a strong economy driven by fishing, agriculture, and foreign trade. Banana farming is famous in the city, which is exported worldwide.

2. What is the state of the coastal currents off Machala?

Local currents along the coast of Machala are produced by a multi-dimensional interaction between a number of factors. The Humboldt Current, one of the largest Pacific Ocean currents, is significant here. It is a cold, nutrient-rich current flowing north along South America's west coast. As it approaches Machala, it interacts with bathymetry and local topography and produces the local coastal currents.

Pacific Ocean tides are also involved. While the tidal range in the open ocean is quite small here, it is sufficient to cause water-level variations along the coast. These can create tidal currents, particularly in shallow estuaries and around narrow channels between islands.

The Gulf of Guayaquil geometry and seabed bathymetry have a strong impact on the coastal currents. The gulf geometry, which is on the middle of the shallow and wide towards the mouth, has a capability to trap and deflect the flow of the current. Submarine structures such as reefs, sandbars, and channels have the capability to converge or disperse the flow of currents. For example, reefs are capable of acting as a barrier and causing the water to flow in a particular manner, while channels tend to accelerate the current.

The presence of rivers and streams that flow into the ocean near Machala also affects the coastal currents. The input of freshwater can create a plume that changes the salinity and density of the coastal waters, which results in the development of a distinct coastal current.

3. How to monitor the coastal water current of Machala?

Surface Drifting Buoy Method

Surface drifting buoy method is an age-old technique for monitoring coastal water currents. Researchers throw buoys with tracking instruments into the sea. Through observations of the drift of these buoys with the passage of time, they are able to find out the direction and velocity of the surface currents. But there are limitations to this method. It only provides information of the surface layer of the water column, and the buoys are very susceptible to wind interference. The wind can push the buoys in a direction that is not representative of the true movement of the underlying currents.

Moored Ship Method

The moored ship method employs a moored ship as a platform for current measurement. The instruments are dropped from the ship to measure the water flow at various depths. While the method can produce detailed vertical profiles of the currents, it has several shortcomings. Its spatial range is limited to the area around the moored ship, and the existence of the ship could interfere with the natural flow of water, which could taint the measurements. In addition, keeping a ship moored for an extended duration can become logistically cumbersome and costly.

Acoustic Doppler Current Profiler (ADCP) Technique

ADCP profiler has been a more advanced and efficient tool for coastal current measurement. ADCPs can measure current in water over a broad vertical range with high-resolution details of water column velocity structure. ADCPs can be mounted on various platforms, from ships and buoys to the seafloor. Ship - mounted ADCPs can continuously take data as the ship travels, covering a broad area in a short period of time. Bottom - mounted ADCPs can provide fixed - point, long - term measurements so that scientists can track long - term trends within the coastal currents.

4. How does the working principle of ADCPs based on the Doppler principle?

ADCPs operate on the Doppler principle. They emit acoustic pulses into the water. The pulses bounce off suspended particles such as sediment, plankton, or bubbles in the water. When the water is in motion, the frequency of the reflected pulses shifts. By measuring this shift in frequency, the ADCP flow meter can calculate the velocity of the water relative to the instrument.

Most ADCPs have multiple transducer beams, usually four or more, at various angles. The multi-beam configuration enables the measurement of the three-dimensional velocity of the water. By combining the signals from these beams, the ADCP can generate a full image of the current velocity at multiple depths in the water column. The information gathered by the ADCP may be analyzed in real-time or archived for subsequent analysis, which is of considerable importance in establishing the dynamics of the coastal currents.

5. What's required for high-quality measurement of Machala coastal currents

For accurate measurement of Machala's coastal currents, the measuring instrument should possess some significant characteristics. It should be made from reliable materials, possess small sizes, light weight, low power consumption, and low cost. These features enable the use of many instruments to provide complete spatial coverage.

Titanium alloy-cased ADCPs are highly recommended. Titanium alloy possesses good resistance to corrosion, which is essential for long - term deployment within the harsh marine environment. Titanium alloy resists the corrosive action of saltwater, and it shields the ADCP 's internal workings from damage. Titanium alloy is also light yet strong, making it ensure portability and durability of the instruments. These factors enable one to achieve accurate and long - term measurements of Machala coastal currents.

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

Usage - Based Choice

The choice of ADCP depends on its usage. Ship-mounted ADCPs are the best for ship-borne measurements. They can provide real-time data as the ship moves in the water, scanning a large area in a relatively short period of time. For long - term observation at a fixed station, bottom - mounted ADCPs are more suitable. They are able to provide continuous data for a long time, and researchers can gain knowledge about long - term trends in the coastal currents. Floating ADCPs are used to track the motion of water masses in broad regions, providing useful information about large - scale circulation patterns.

Based on Depth Selection

The frequency of the ADCP should also be chosen based on water depth. For water depths less than 70m, 600kHz ADCPs can be used. They can provide high-resolution measurements in shallow water. For depths up to 110m, 300kHz ADCPs are applicable. For deeper waters up to 1000m, 75kHz ADCPs can be employed.

There are numerous well-known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. To others who must look for budget-friendly options, however, the ADCP manufacturer China Sonar's PandaADCP is actually worth looking into. Made entirely of titanium alloy, it provides excellent performance at a very affordable price. It's an excellent choice for budget-conscious users who also require good-quality ADCPs for the measurement of coastal currents. To learn more, go to their webpage: https://china-sonar.com/.

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