How to Measure the Water Current of the Markha River

1. Where is the Markha River?

The Markha River is situated in the Ladakh region of India. It passes through a high-altitude desert landscape and is part of the local hydrological system.

The land the river flows through is very hostile, comprising cold winters that last a number of months and summers that are relatively short. Villages along the Markha River are very thinly spread out, while nomadic communities are more present. The river is an important water source for these communities, providing water for domestic use and for their livestock. The topography of the area comprises mountains and valleys and the Markha River a distinctive feature in this semi-arid terrain.

2. What is the character of the flow rate in the Markha River?

The discharge in the Markha River is variable according to seasons and climate. During spring and early summer, the flow is significantly increased by the melting of snow from surrounding mountains. The breaking of ice and snow launches an immense quantity of water down the channel and produces a relatively -high flow.

During the late summer and fall, as the snowmelt influence diminishes, the flow rate decreases. During the winter, the flow rate is greatly reduced and may freeze over entirely under extremely cold conditions. The average flow rate can vary in range from just a few cubic meters per second during the low-flow winter period to several hundred cubic meters per second at the peak of the spring snowmelt.

3. How to measure water current of the Markha River?

Velocity Meter Method

This conventional method involves the use of mechanical or electronic velocity meters. These are strategically positioned at select points in the river, whereby the actual velocity at that point is directly measured. Nevertheless, complete information about the general water current requires multiple measurements taken at various levels of depth and across different parts of a river. The length and variability in conditions within the Markha River make this convention somewhat labor- and time-intensive.

ADCP Method

ADCP profiler represents a more sophisticated and handy method of water current measurement. It uses the sound waves to detect the movement of the water particles. While producing acoustic signals and analyzing the Doppler shift of the reflected signals, it is able to measure the velocity of water simultaneously at several depths. This gives a very accurate profile of the water current, and allows for a much better analysis of the flow conditions over the entirety of the river. ADCPs can be mounted on boats, provided the river is navigable, bridges, if available, or deployed on buoys for continuous monitoring.

Buoy Method

In the buoy method, buoys are set in the river with sensors that measure the movement of the water around them. These buoys float on the surface, and they are able to carry some indication from the surface current. However, they may not capture the full complexity of the water current as accurately as the other methods, especially when it comes to understanding the variations in velocity at different depths.

Out of these, the ADCP current meter is an advanced and effective tool for measuring the water current of the Markha River.

4. How do Doppler principle-based ADCPs work?

ADCPs work on the principle of the Doppler effect. When an Acoustic Doppler Current Profiler (ADCP) sends out an acoustic signal into the water, the sound waves travel through water and reflect back from moving water particles. Because the water particles are in motion, the frequency of the reflected sound waves changes due to the Doppler effect.

The reflected wave frequency will be higher if the water particles are moving towards the ADCP flow meter. Conversely, if the water particles are moving away from it, the reflected wave frequency would be lower. By precisely measuring this change in frequency, the ADCP is able to calculate the velocity of the water particles at different depths.

From these, the ADCP meter then combines the individual velocity measurements at various depths to develop a complete profile of the current in the water. This can provide a very detailed insight into how the water is flowing, not only at the surface but even through the vertical section of the river.

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

Since the Markha River Currents measurement should be of high quality, the equipment needs to have the following characteristics.

High material reliability of the equipment is essential. The equipment must be resistant to unfavorable conditions in the river, such as water, sediment, and temperature fluctuations. The variable flow of the Markha River and the presence of ice and debris during high-flow and freeze-thaw periods require durable equipment.

It is also desirable to achieve small size, lightweight, and low power consumption. The compact and lightweight device provides the user with ease of handling and deployment, especially in such remote and harsh conditions of the Ladakh region. Low power consumption allows it to keep the equipment running for long periods of time without the need for replacing batteries often or finding a continuous power source.

Cost-effectiveness is a crucial aspect. A lesser expense for the sensor opens up the possibility of utilizing more measurement equipment for wider area coverage to monitor the river.

In terms of casing, the ADCP flow meter can be made from titanium alloy. It is for this reason that titanium alloy has a high resistance to corrosion, which is quite essential since the equipment will always come into contact with water from the Markha River, as well as other substances that could be corrosive in nature. In addition, it is relatively strong and durable enough to withstand physical impacts and pressure changes expected during its deployment and operation. The density of the titanium alloy is relatively low, which also contributes to the general objective of keeping the equipment lightweight.

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

In selecting the appropriate equipment for measuring the Markha River current, some influential factors must be considered.

Based on the Purpose of Use

In case the intention is to measure the horizontal cross-section of the river current, a horizontal ADCP current profiler should be used. HADCPs are designed to give precise measurements of water flow in the horizontal plane and, thus, are useful for understanding the overall movement of water across a given section of the river.

If the purpose of the measurement is to assess the river current vertical cross-section, a vertical ADCP current meter shall be chosen. Vertical ADCPs can accurately record water velocity at each specific depth, which provides a depth profile of water flow vertically across the river.

Based on Frequency

The choice of frequency depends on the depth of the water in the Markha River. Usually, for water depths up to 70 meters, a 600 kHz ADCP should be quite adequate. This 600 kHz frequency provides good resolution and accuracy in the measurement of water current in relatively shallower waters.

The ADCP 300 kHz is better suited for deeper waters, for instance, over 70 m to approximately 110 m. The 300-kHz lower frequency can penetrate deeper into the water and further guarantee reasonable measurements of water current.

There are renowned brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective option with excellent quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, ensuring durability and reliability. With its remarkable cost - performance ratio, it provides a great alternative for measuring the water current of the Markha River. You can find more information about it on its official website: https://china-sonar.com/.

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