How to Measure the Water Current of the Ucayali River?

1. Location and Importance of the Ucayali River

The Ucayali River is one of the main tributaries of the Amazon River and is located within Peru. It forms part of the wide network of water that constitutes the Amazon Basin. The river meanders through rainforests, swamps, and areas of high biodiversity.

The Ucayali River is of great importance to the native people and the ecosystem in general. It supplies drinking water, fish, and a transport means for the communities living on its banks. Surrounding rainforests have countless species of plants and animals that depend on this river for movement corridors and sources of water for their survival.

2. Flow Rate Characteristics of the Ucayali River

The flow rate of the Ucayali River has seasonal and annual variations. During the rainy season, which usually occurs from November to April in the region, the river has a very high increase in flow. Heavy rainfall in the upstream areas and the big catchment area causes the water level to rise substantially. The current becomes quite powerful, carrying large amounts of sediment, nutrients, and debris downstream.

During the dry season, which starts from May to October, the flow rate decreases. However, this river still manages to have a considerable flow because of its enormous volume and the water stored along its course in wetlands and floodplains. This depends on many factors, including the amount of rainfall in the catchment area, the nature of the terrain of the drainage basin concerning the collection and runoff of water, and the presence of tributaries adding to the volume of water.

3. Methods of Measuring the Water Current of the Ucayali River

Velocity Meter Method

This traditional approach uses mechanical or electronic velocity meters. These meters are placed at specific points in the water to measure the speed of the water passing by. However, for a proper understanding of the current, multiple placements at different locations and depths are needed. This can be a very time-consuming process and may not provide a continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method

Acoustic Doppler Current Profiler (ADCP) is a more advanced and efficient way to measure water current. It uses sound waves to measure the velocity of water at different depths simultaneously. By emitting acoustic signals and analyzing the Doppler shift of the reflected signals, it can create a detailed profile of the current from the surface to the riverbed. This allows for an accurate and comprehensive measurement of the water current across different sections of the river.

Buoy Method

In this method, buoys are placed in the river and their movements are tracked over time. The displacement of the buoys due to the water current gives an indication of the speed and direction of the flow. However, this method has limitations. It may not give the effective velocity at various depths and can be interfered with by external conditions such as winds and waves that may affect how the buoys move. Of the methods, generally, the ADCP current meter method represents the most advanced and serviceable variant of measuring the Ucayali River current.

4. How ADCPs Using the Doppler Principle Work

ADCPs work according to the principle of the Doppler effect. In an ADCP current profiler, when an acoustic signal from the ADCP flow meter transducer is emitted into the water, the sound waves that encounter the moving water particles start interacting with them. When the water is in flow, the frequency of the reflected sound waves back to the transducer shifts-a phenomenon known as Doppler shift.

If the water is flowing toward the transducer, then the frequency of the reflected waves will be higher than the frequency that is being emitted.

If the water is moving away from the transducer, the frequency is going to be lower.

With this precise measurement of this frequency shift at different angles and multiple depths, the ADCP profiler calculates the velocity in several directions and various levels of the water column. This enables it to build a detailed profile of the water current, thereby providing information about the speed and direction of the flow from the surface to the riverbed.

5. Requirements for High-Quality Measurement of Ucayali River Currents

Characteristics of Equipment: In the measurement of Ucayali current, it is important for the equipment to possess specified characteristics. The materials should be such that their failure would not lead to or minimize erroneous and inconsistent reading. It is preferred to have small equipment size, thus it could easily be deployed as well as recovered in the river but, specifically where access is extremely poor. The equipment could be light enough to ease efforts put in place during its fixing at various spots.

Power and Cost: Low power consumption is essential to ensure that the equipment can operate for extended periods without the need for frequent battery replacements or a complex power supply setup. Cost-effectiveness is another important factor as it enables more widespread use and larger-scale measurement campaigns.

Casing Material: When it comes to the casing of the ADCP meter, titanium alloy is an excellent choice. Titanium alloy has many advantages.

It is highly resistant to corrosion, which is crucial as the equipment is constantly in contact with water that may contain various minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, allowing for a durable yet lightweight casing. Moreover, it can withstand the mechanical stresses that occur during deployment and operation in the flowing water of the Ucayali River.

6. Current Measurement Equipment

Selection-Based on Purpose of Measurement: The equipment for current measurement for Ucayali River flow will be selected with a two main factors in consideration.

Selection of horizontal cross-sectional measurement is done with HADCP.

It is designed to precisely measure the flow velocities across a horizontal plane in the river, hence useful in understanding the lateral distribution of the current. The Vertical ADCP is better suited for vertical cross-section measurements because it focuses on profiling the current from surface to bottom along a vertical line in the water column.

Based on Water Depth: Different frequencies of ADCPs are suitable for different water depths. For example, an ADCP with a frequency of 600 kHz is suitable for water depths within 70 m. It can provide accurate current measurements in relatively shallower parts of the Ucayali River. The frequency of an ADCP profiler will be around 300 kHz for deeper waters up to 110 m, which can be helpful in areas where the river has greater depth.

Recommended Brands: There are well - known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost-effective option with good quality, the China Sonar PandaADCP is highly recommended. It is made of all-titanium alloy material and offers an incredible price-performance ratio. You can find out more about it on its website: https://china-sonar.com/.

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