How to Measure Water Current of Narmada River?

1. Where is Narmada River?

The Narmada River is one of the most important rivers in India. It originates from the Amarkantak Plateau in Madhya Pradesh and, after running westmost across the Indian subcontinent through the states of Madhya Pradesh, Maharashtra, and Gujarat, it ends.

This river cuts across a variety of topography. It flows through thick forests housing various types of flora and fauna. The riverbanks host many small and big settlements. Cities like Jabalpur in Madhya Pradesh and Bharuch in Gujarat have come up along its course. The Narmada River forms an important source of water supply for these urban and rural centers, providing water for drinking as well as irrigation and industrial purposes.

It holds a place of eminence culturally in Hindu mythology and is considered a holy river. A number of temples and places of pilgrimage, festivals like Narmada Jayanti, are conducted along its banks to commemorate the river. The flow of the river has been intrinsic to the cultural and religious heritage of the region since time immemorial and continues to be at the heart of the people's spiritual lives.

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

The flow rate of the Narmada River is seasonal. During the monsoon, which generally lasts from June to September, the river receives a heavy amount of water from its catchment area. The water level rises, and the flow becomes quite strong with high velocity. This period is vital for the recharging of groundwaters and filling up all the reservoirs and dams constructed across the river for storage and irrigation purposes.

During the non-monsoon months, the rate of flow diminishes. However, the river still possesses a regular flow that is critical for the survival of the ecosystems and the water requirements of the local people. The average flow rate depends on the amount of rain in the upper reaches of the river, the efficiency in the management systems of water like dams and canals, and the nature of topography of the river basin that decides the rate of runoff and collection of water.

3. How to measure water current of Narmada River?

There are several ways through which the water current of the Narmada River can be measured:

Velocity Meter Method: The most classic way is by using the mechanical or electronic velocity meter. This has to be placed at various strategic positions in water to determine the speed of the running water. However, a number of placements at several locations and depths are essential to obtain a proper realization about the current. It may be rather time-consuming and may not always give a continuous profile of the current throughout the column of water.

Acoustic Doppler Current Profiler (ADCP) Method: The ADCP method is an advanced and efficient way of measuring 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 the measurement of water current across different sections of the river in greater detail and accuracy.

Buoy Method: In this technique, buoys are set in the river and their movements are monitored 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 provide accurate velocity measurements at different depths and can be affected by external factors such as wind and waves, which can influence the movement of the buoys.

Among these, the ADCP method is more advanced and convenient for the measurement of the water current of the Narmada River.

4. How do ADCPs using the Doppler principle work?

ADCPs work by using the Doppler effect. An acoustic signal that is emitted from the ADCP transducer into the water causes the sound waves to interact with the moving particles of water. Since the water is in flow, the frequency of the reflected sound waves back to the transducer shifts; this shift is what is commonly referred to as the Doppler shift.

Thus, for a given flow direction either to or away from the instrument, the frequency of reflected waves in motion will be higher or lower when compared to the frequency being emitted. With the facility for precise measurements of frequency shift at a range of angles and multiple depths, the ADCP is therefore in position to determine the water's velocities along different directions and along the depth range in that water column. This enables it to create a detailed profile of the water current, thus providing valuable information on the speed and direction of the flow from the surface to the riverbed.

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

The equipment for measurement of the currents of the Narmada River should have some characteristics that ensure high-quality measurement. The materials used in its construction should be reliable to give correct and repeatable measurements. Small size is an advantage for easy deployment and retrieval in the river, especially at sites which are difficult to access. The equipment should be lightweight to simplify the installation process and reduce the effort needed for handling.

It ensures that the equipment will have low power consumption, hence can operate for extended time without the need to frequently change the batteries or setting a complex power supply setup. Cost-effectiveness also enables more widespread use and allows larger-scale measurement campaigns.

Titanium alloy will be good for the casing of ADCP. Titanium alloy has several advantages. It is very resistant to corrosion, which is vital since the equipment is in constant contact with water that could contain a variety of minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, which will enable a robust yet light casing. Furthermore, it is able to resist mechanical stresses during deployment and operation in the flowing water of the Narmada River.

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

Choosing the right equipment for the measurement of the current of the Narmada River, the following two aspects are the most important concern:

First, depending on the purpose of use, in horizontal cross - section measurement, the Horizontal ADCP, HADCP, will be suitable. The horizontal ADCP is designed to measure the flow velocities over a horizontal plane in the river quite accurately, which helps in ascertaining the lateral distribution of the current. For a vertical cross-section measurement, the Vertical ADCP is more appropriate because it will focus on profiling the current from surface to bottom along a vertical line in the water column.

Different frequencies of ADCPs are suited for different water depths. For instance, 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 Narmada River. An ADCP with a frequency of 300 kHz is more appropriate for deeper waters up to 110 m, which can be useful in areas where the river has 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.