How to Measure Water Current of Mantaro River?

1. Where is Mantaro River?

The Mantaro River is one of the most important water resources in Peru. It flows across landscapes that vary from highland to fertile valleys, hosting a rich biodiversity. Well, it originates in the Andean highlands and cuts right through the heart of the country.

It crosses many settlements and cities during its course. These urban and rural areas depend on the Mantaro River for many reasons. The river is a source of domestic water for drinking, cooking, and cleaning among the inhabitants of this region. The agriculture of this region also depends on this river. It supplies water to the fertile valleys where wheat, barley, and a variety of vegetables are grown. It has a very complex network of canals that divert water from Mantaro for irrigation, which sustains farmers' livelihoods and the economy within the locality.

The Mantaro River is culturally important, and its place is held dear in the traditions and heritage of the local communities. There has been a long coexistence of indigenous cultures with this river, passing on stories and legends of its importance. The riverbanks are often the site of local festivals and religious ceremonies, highlighting its importance as a symbol of life and prosperity.

2. What are the general features of the flow rate in Mantaro River?

The Mantaro River is one such river in nature whose flow rate often presents huge seasonal and annual variability. Normally, during the wet season-occurring from November to April in the region-the flow considerably increases in this river. Rainfall in the upper catchment areas and the melting of glaciers in the high Andes contribute to a rise in the level of water. The current becomes very strong during this period, carrying enormous amounts of sediment and nutrients downstream.

During the dry season, which extends from May to October, the flow rate decreases. The river, however, still flows with contributions from groundwater and the release of water from reservoirs. The average flow rate is affected by a multitude of factors. The amount of precipitation in the upstream regions, the rate of glacial melt, the topography of the river basin (which determines how water is collected and drained), and the operation of water management structures such as dams and canals all play a role in shaping the flow characteristics of the Mantaro River.

3. C‌mo medir la corriente de agua del Ro Mantaro?

There are various ways to measure the Mantaro River water current, such as:

Velocity Meter Method

This traditional technique employs 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, to get a comprehensive understanding of the current, multiple placements at different locations and depths are necessary. This can be very time-consuming and may not provide a continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP flow meter technique is one of the newer, much more efficient ways of measuring water current; it depends on the reflection of sound waves to measure the velocity of water simultaneously at different depths. By emitting an acoustic signal and analyzing the Doppler shift of the reflected signal, a detailed profile of the current can be created from the surface down to the riverbed. In this way, the actual measurement of water current over various sections of the river is far more accurate and comprehensive.

Method of Buoy

The method will then involve placing buoys in a river and observing their motions over time. From here, this could give an indication of the speed and direction of flow, since the buoys will shift in one direction because of the water current. This technique also has a number of drawbacks. The velocity at varying depths may not be delivered accurately, and environmental conditions like wind and waves can alter the traveling buoy.

Among these methods, the ADCP current meter method is the more advanced and convenient option for measuring the water current of the Mantaro River.

4. How do ADCPs using the Doppler principle work?

The basic operating principle of ADCPs is the Doppler effect. When an acoustic signal is transmitted from the ADCP flow meter transducer into the water, the sound waves interact with the moving water particles. As the water is in flow, the frequency of the reflected sound waves back to the transducer changes-a phenomenon referred to as the Doppler shift.

If the water is moving towards the transducer, then its reflected waves will have a higher frequency compared to the frequency at which it was emitted. Conversely, if the water is moving away from the transducer, then the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP meter is able to calculate the velocity of the water in different directions and at different levels within the water column. This enables it to make a highly detailed profile of the water current and thus derive precious information about the speed and direction of flow from the surface down to the riverbed.

5. What's needed for high-quality measurement of Mantaro river currents?

The equipment for high-quality measurement of Mantaro River currents should possess certain characteristics. The materials used in its construction need to be reliable to ensure that the measurements are accurate and consistent. A small size is beneficial as it allows for easier deployment and retrieval in the river, especially in areas with difficult access. The equipment should also be lightweight to simplify the installation process and reduce the effort required for handling.

The power consumption shall be low in order for the equipment to work for long periods without frequently replacing batteries or having complex and costly arrangements of power supply. Cost - effectiveness is another important factor because it could facilitate the wider use and larger-scale measurement campaigns.

Regarding its case, the best material used on ADCP profiler is a Titanium alloy. The advantages of a Titanium alloy include. It is highly resistant to corrosion, which is very important because the equipment is in constant contact with water that may contain many minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, allowing for a durable yet lightweight casing. Besides, it is resistant to the mechanical stresses during deployment and operation in flowing water in the Mantaro River.

6. How to Choose right equipment for current measurement?

When it concerns selecting the right equipment for the Mantaro River current measurement, two factors are mainly considered.

Accordingly, as for usage purpose, in horizontal cross-section measurement, Horizontal ADCP is suitable. It is specially designed to accurately measure flow velocities across a horizontal plane in the river, as it helps to understand lateral distribution of the current. In the case of vertical cross-section measurement, the Vertical ADCP is more appropriate because it focuses on profiling the current from the surface to the bottom along a vertical line in the water column.

Second, ADCPs with various frequencies suit different water depths. An example is that the ADCP meter, having a frequency of 600 kHz, suits water depth up to 70 m; with th0is, one would carry out quite accurate current measurement in relatively shallower parts of Mantaro River. While at the same time, 300 kHz will be more suited in deeper waters of up to 110 m, useful in such zones where the river would also have greater depth.

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.