Why We Measure the River Flow of Asansol？

1. Where is Asansol?

Asansol, India's second city in the state of West Bengal, is located in the eastern part of India. Geographically, it is located at approximately 23.41°N latitude and 86.84°E longitude. Located in the valley of the Damodar River, the city encircles a terrain that combines rolling hills and fertile plains. The location falls in the Chota Nagpur Plateau, which offers the context of rolling land with intervening flat areas available for cultivation and urbanization. This geography has shaped Asansol's growth and development with respect to the surrounding water courses.

Asansol is historically and culturally vibrant and has its growth firmly associated with industry. The city has been an important industrial center right from the British colonial period, as coal mines, railways, and industries have been set up. The industrialization brought masses of people from other regions of India and created a melting pot of cultures. Asansol is famous for its local festivals like Durga Puja, which are celebrated with immense fervor, representing the fusion of various cultural practices. The city is also rich in history, and with the existence of the remnants of British-era structures, old railway stations, and factories, all of which bear witness to its past.

The Damodar River is the prime river system that has a deep impact on Asansol. Previously known as the "Sorrow of Bengal" due to its frequent and devastating floods, the Damodar River originates in the Chota Nagpur Plateau in the state of Jharkhand. It flows for around 541 kilometres in a more or less eastward direction, finally merging with the Hooghly River. The Damodar River has been boon as well as bane to Asansol. Historically, it provided water for purposes of utilization and was a medium of transport for commodities, mainly coal, which was predominant in the local commodity market. However, the river's erratic flow regimes are further compounded by deforestation, mining activities, and changed land - use patterns in its catchment, resulting in regular flood disasters, which are exacting a toll in human lives and property. More recently, efforts have been made to control the river's flow by constructing dams and barrages, but the control over its flow remains critical for the sustainable development of Asansol.

2. What is River Flow at Asansol?

There are many factors influencing the river flow at Asansol. The precipitation and runoff do have the greatest impact. There is a tropical monsoon climate prevailing in the area, with the monsoon season from June to September. Heavy and largely intense rainfall occurs during these months, which causes the sudden increase in the water level and flow rate of the Damodar River. Runoff from the neighboring hilly slopes and plains also supplies water into the river, which builds its volume. On the contrary, dry periods from October to May witness severely low water levels, with slow-moving flow. Climate change has disrupted the usual rhythm of rainfall, leading to more unpredictable monsoons, with higher rains in a shorter duration and more lengthy dry spells, casting a shadow of both floods and droughts.

The terrain and river morphology also affect the flow. The Damodar River flows in hilly country made up of narrow gorges, rocky outcrops, and wide floodplains. In the hilly regions upriver, the gradient is steep and thus the flowing water is quicker. When the river approaches Asansol and enters the flat Damodar River valley, the river becomes broad and forms wider and shallow reaches. The channel of the river, which is made up of a mixture of sand, gravel, and silt, is susceptible to erosion and deposition, hence always modifying the size and shape of the river, influencing the local patterns of flow.

In the direction towards the upstream, there are dams and barrages such as the Maithon Dam and the Panchet Dam. These discharge water in regulated ways. These were built to control floods, generate hydroelectric power, and provide water for irrigation and industry. However, operation of such dams is capable of both negative and positive influences on the stream flow in the downstream. Although they minimize flood severity, improper management of water release generates low stream levels during the dry season, affecting water supply for domestic, agricultural, and industrial purposes in Asansol.

3. How to Observe the River Flow in Asansol?

Traditional means of measuring river flow include the surface drift buoy method and anchored boat measurement.

The surface drift buoy technique is simple and primitive. The floats are released on the water surface, and their movement over a known distance and time period is recorded. This provides a measure of the surface flow velocity. This technique has limitations. It only samples the flow in the surface of the water and might not be representative of the flow in the entire body of water. In addition, the wind will influence the movement of the buoys and cause erroneous readings, especially in open stretches of the river.

The anchored boat method is to moor a boat at a point in the river. A current meter is dropped in the water at various levels to measure the velocity of the flow. The method gives a more detailed profile of the flow at the location. However, it is time - consuming, manpower - consuming, andunsafe, especially in flowing or turbulent water. It requires vast resources and manpower to conduct measurements at points along this method.

Acoustic Doppler Current Profilers (ADCPs) offer a more advanced and easier alternative. ADCPs are not needed to make physical contact in order to measure the water velocity at different depths across the water column. They are non - invasive. They can quickly generate detailed flow profiles, scanning large stretches of the river in a matter of hours. They are thus especially suitable for the continuous monitoring of the dynamic and intricate river currents surrounding Asansol, considering the changing topography of the river and the need for comprehensive data collection.

4. What Is ADCP, Which Uses the Doppler Principle?

ADCPs operate based on the Doppler principle. They release acoustic pulses into the water. When the signals travel in the water, they interact with moving particles, like suspended sediment, plankton, or microbes. When the signals bounce off moving particles, the frequency of the reflected signals is shifted according to the velocity of the particles relative to the ADCP. With these frequency variations, the ADCP calculates the velocity of the water at different depths and constructs a full profile of the river current. This offers accurate measurement of flow velocities, directions, and river dynamics, and provides useful data for hydrological studies and management of water.

5. What is Required for High-Quality Measurement of River Flow in Asansol?

For accurate high-quality river flow measurement using ADCP in Asansol, certain equipment specifications are needed. Material robustness is a top priority. The ADCP should be robust enough to withstand the abrasive river environment and exposure to sediment-laden water, changing water depths, and potential collision by floating debris. Top-grade, corrosion-resistant material such as titanium or specialized polymers ensures device robustness and prolonged usage.

Size and weight are also of particular significance. Lighter and smaller ADCP is simpler to transport and install, especially in the sometimes remote - access areas around the Damodar River along Asansol. Such portability allows for greater flexibility in data collection, enabling researchers and water managers to travel to different segments of the river for accurate readings.

Cost-effectiveness is also a significant factor. For Asansol's long-term or large-scale monitoring activities, a high-quality-performing ADCP at a reasonable cost is the choice. This allows comprehensive monitoring of the river current without straining the budget, allowing frequent and large-scale measurements to characterize and control the river processes more effectively.

6. How to Choose the Right Current Measurement Equipment?

Deployment Methods

• Boat-mounted (mobile boat) ADCP: Perfect for survey, river discharge measurement, and generating high-quality maps of the flow. It can make quick measurements of extensive stretches of the Damodar River, allowing data collection at various points. It can be used to uncover the overall flow patterns in the river and parts prone to erosion or sedimentation.
• Fixed bottom-mounted ADCP: Ideally employed for long-term continuous monitoring. Once installed on the riverbed, it can continuously collect data over time, providing valuable information on long-term changes and trends of the river flow. This can be employed in monitoring the environmental impacts of water management activities and the impact of climate change on the river.
• Cableway ADCP: If there is a cableway in river reaches, then a cableway ADCP can be used. It is placed above the river and can measure the flow over the river at a single point. This works well in obtaining accurate and frequent flow information at main locations in the river that can be used in calibration and validation of other measurement tools.

Working Frequency

The frequency at which an ADCP operates determines its range and resolution. It would have a range of about 70 meters in the case of a 600 kHz ADCP, and it would be suitable for relatively shallow sections of the Damodar River or for taking high-resolution measurements in deeper sections. A 300 kHz ADCP, on the other hand, measures up to 110 meters and is better suited for deeper sections of the river. Higher frequency gives greater resolution but less range, while lower frequency gives greater range but poorer resolution. The frequency to be employed is determined by the specific characteristics of the river and by the requirements of the measurement, such as the level of detail to be achieved and the extent of maximum water column depth to be measured.

Brand Recommendations

Globally, well-known brands of ADCPs include Teledyne RDI, Nortek, and SonTek. These brands are well-known for their quality products, state-of-the-art technology, and consistent performance. However, if one desires a low - cost option, the ADCP manufacturer Chinese brand "China Sonar Panda ADCP" is an ideal choice. This "economy ADCP" is made of all - titanium alloy material, which is extremely robust and corrosion - proof. It is extremely cost-saving, hence applicable for a wide range of uses, from small-scale research work to neighborhood water management projects. For more information, you can visit their site at https://china-sonar.com/.

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