How to measure water current of Lerma River?

1. Where is Lerma River?

The Lerma River is an important watercourse in central Mexico. It passes through the states of Michoacán and México, among others. The river runs through a varied landscape including agricultural areas, urban parts, and areas of outstanding natural beauty.

The agricultural sectors are particularly dependent on the source for irrigation to support corn, wheat, and most vegetable crops. As the river meanders through most urbanized cities like Toluca, it has had a great influence on its city-building and supplying water to them. There is a variety of vegetation lining the banks of the river, including reeds and grasses in many forms. The Lerma River also provides a home to many species of animals, such as fish-species carp and catfish, and birds like herons and kingfishers.

2. What is the flow rate of the Lerma river?

The flow rate of the Lerma River is very irregular. It gets much swollen and increases its flow during this wet season, normally between June and September in the region, by heavy rainfall and runoff contributions that mostly take place over the catchments area. The water rushes with a relatively high velocity along the bed downstream, with quite substantial discharge. The high - flow period might see velocities reaching [provide an estimated range like 0.8 - 2.0 meters per second] and discharges in the range of [mention an estimated volume such as 50 - 200 cubic meters per second].

During the dry season, which occurs between October and May, the rate of flow reduces drastically; the river becomes shallow with an average flow velocity considered to be from 0.1 - 0.5 meters per second, and the discharge could go as low as 10 - 30 cubic meters per second during this period. This dramatic variation in flow rate signifies fluctuating water availability levels for agricultural and domestic consumption.

3. How to measure water current of Lerma River?

There are several methods to measure the water current of the Lerma River.

The velocimeter method: Involves application of the traditional technique in using mechanical or electrical velocimeters. These instruments, at different depths and over different locations of the area of the river, receive placement. This method gives an estimate by direct measurement of the speeds of flow at the various set points. This process could be very laborious since a lot of time shall be spent on just some minute areas of the entire coverage area of the river.

Acoustic Doppler Current Profiler (ADCP) method: ADCP current meter is more advanced and efficient. It sends acoustic signals into the water column and analyzes the Doppler shift of the reflected waves, hence enabling it to measure the velocity of water at several depths simultaneously. In comparison with the velocimeter method, ADCP can provide a more comprehensive and detailed view of the flow conditions in the river in a much shorter time.

Buoy method: Buoys equipped with sensors or tracking devices are placed on the surface of the Lerma River. The observation of the movements of the buoys for a certain period provides an approximation of the speed and direction of surface current. This method mainly deals with the surface flow and is not representative for deeper depth conditions.

Of the available methods, the ADCP current profiler is at this time the most progressive and efficient means of measuring Lerma River water current; this is because, with relatively less effort, it provides detailed multi - depth data.

4. How do the Doppler Principle ADCPs Work?

The ADCPs operate on the principle of the Doppler effect. They emit acoustic pulses of a known frequency into the water. When these sound waves encounter moving particles in the water, such as sediment particles or small organisms, the frequency of the reflected waves changes. This is what is called the Doppler shift.

If the particles are moving towards the ADCP flow meter, then the reflected frequency is higher than the emitted one, and vice versa. By accurately measuring this shift in frequency, considering the angle at which the acoustic signals were emitted and received, the ADCP meter can determine how fast the water is at each depth. Multiple transducers on the ADCP profiler are usually mounted in various orientations to measure flow velocities in different directions, including horizontal and vertical components. This is possible because it can produce a detailed profile of the current in the water flowing within the river.

5. What is necessary for high-quality measurement of Lerma River currents?

The equipment to be used for measuring the currents of the Lerma River should possess certain qualities for high-quality measurement. First, the materials on which the measuring devices are made should be of good quality and reliable. They should be strong enough to bear the hazardous conditions of the river atmosphere, including possible impacts from floating debris and changes in temperature and quality of water.

Second, the equipment should be small in size, light in weight, and have low power consumption. A compact design makes deployment and retrieval easier, particularly in a region where access to the river might be somewhat difficult because of the terrain or lack of infrastructure. Low power consumption means that the equipment can run for long hours without the need for constant battery replacement or an external power source.

Another important factor in large-scale measurement is the cost of the device. In general, for ADCPs, titanium alloy is a perfect casing material. There are several advantages of using a titanium alloy. It has excellent corrosion resistance; therefore, it can stand in the river water for quite a long period of time without significant damage. It is also strong and durable, able to resist mechanical stresses such as those caused by water currents and even accidental impacts. Also, it is relatively light in weight compared to a lot of other metals, which makes it suitable for equipment used in water current measurement.

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

When choosing the right equipment for measuring the current of the Lerma River, consider the following. Thus, Horizontal ADCP can be employed for measurements in the horizontal cross-section of flow. The ADCPs which are to measure flow features correctly in the horizontal plane take this form. On the other hand, for flow measurements concerning the vertical section, a Vertical ADCP would be highly appropriate. Since one considers measuring the flow properties along every point on a vertical, this model can be taken.

Besides, different frequencies of ADCPs are suitable for different water depths. For instance, an ADCP with a frequency of 600 kHz is well-suited for water depths within 70 meters. It can provide clear and accurate measurements in the relatively shallower parts of the Lerma River. Meanwhile, an ADCP with a frequency of 300 kHz is more appropriate for water depths up to 110 meters, enabling effective measurement in the deeper sections of the river.

There are well-known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, for a cost - effective yet high-quality option, the China Sonar PandaADCP is worth considering. It is made of all-titanium alloy material, ensuring its durability and reliability and offering an excellent cost-performance ratio. You can find out more about it on its official website: https://china-sonar.com/.

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