Why Do We Take the River Flow in Dibrugarh?

1. Where is Dibrugarh?

Dibrugarh, a significant city of the Indian state of Assam, is located in the north-eastern part of India. Geographically, it is located at around 27.31°N latitude and 94.76°E longitude. Picturesquely placed on the southern banks of the Brahmaputra River, Dibrugarh is surrounded by greenery all around. The city holds the Brahmaputra Valley, which is characterized by an overwrought area of flatland and scattered hill tracts, especially towards its eastern boundaries as it meets the Patkai Hills. This is the type of geography that has been instrumental in helping Dibrugarh develop, making the city a significant center for tea production, trade, and transportation in Assam.

Dibrugarh is a vibrant mosaic of diverse traditions historically and culturally. It has been a melting pot of various ethnic individuals, including Assamese, Tai - Ahom, and other indigenous tribes. The culture of the city is best described by its festivals, music, dance, and cuisine. Bihu, the most celebrated festival of Assam, is observed with great enthusiasm in Dibrugarh with colorful folk dances, traditional songs, and festooned clothes. Historically, Dibrugarh has experienced the rule of several dynasties, with the Ahom Kingdom leaving its imprint upon its architecture, administration, and society. It is also significant in the colonial history of India as it developed into an important center for the British tea - plantation economy, leading to the establishment of a number of tea gardens which persist to this day.

The Brahmaputra River is the lifeblood of Dibrugarh. Started in Tibet, China, in the Chemayungdung Glacier and flowing east as the Yarlung Tsangpo River before entering India and becoming known as the Brahmaputra, the mighty river flows through the state of Assam. In Dibrugarh, the Brahmaputra is multifaceted. It is a vital source of water for household use, agriculture, and industries. Historically, it was an important commercial route, employed in the movement of tea, timber, and other commodities, thereby contributing significantly to the economic growth of the city. The river also sustains a rich and diverse ecosystem with various fish species, birds, and aquatic flora. However, the unpredictable nature of the Brahmaputra, especially during monsoon, has a tendency of causing floods, which are an ongoing threat to the city and its inhabitants.

2. What is the River Flow around Dibrugarh?

Rainfall and runoff are the primary driving forces for river flow around Dibrugarh. The region has a tropical monsoon climate, and the monsoon season extends from June to September. There is heavy and steady rainfall during this period, primarily in the upper catchment areas in the Himalayas and surrounding hills. The rainfall causes a tremendous increase in the velocities and levels of water of the Brahmaputra River through the runoff. The volume of water increases and the speed picks up as it flows towards Dibrugarh. In contrast, the level of the water decreases significantly between the months of October and May, and the flow reduces significantly. Climate change has further exacerbated the scenario, with more variable monsoon patterns, increased precipitation in fewer days, and extended dry spells, increasing the frequency and magnitude of flood and drought events.

Topography and river morphology are equally significant parameters affecting the flow. The Dibrugarh reach of the Brahmaputra River traverses a landscape made up of wide, flat floodplains. The sediment- and sand-filled riverbed is constantly being deposited and eroded. This keeps on causing the river to change course over a span of time, and oxbow lakes and meanders are created. The role of tributaries like the Disang and Burhi Dihing rivers, which join the Brahmaputra near Dibrugarh, influences the flow dynamics. These tributaries add to the quantity of water and even reverse the direction and rate of the principal river flow.

There are barrages and dams upstream on the Brahmaputra's tributaries, which are mostly harnessed for irrigation, hydropower, and flood control. While these can control the water flow to some extent, their operation also impacts the downstream areas, such as Dibrugarh. Incorrect calculation in the release of water or hasty heavy rainfall upstream leads to sudden rises in water level, which in turn create floods in Dibrugarh.

3. How to Measure the River Flow in Dibrugarh?

The conventional methods of measuring river flow are the anchored boat method and the surface drift buoy method.

The surface drift buoy method is a rudimentary technique. Floats are released on the river surface, and their movement over a measured distance and duration of time is tracked. This provides an estimate of the surface velocity of flow. But this technique has some disadvantages. It only observes the flow at the surface, which might not be representative of the flow through the whole water column. Additionally, wind and other surface-level disturbances might affect the buoy motions, and hence measurements are not reliable.

Anchored boat method involves anchoring a boat in a location in the river. A current meter is dropped in the water at various depths to measure the velocity of flow. It gives a more accurate profile of the flow at the location. But it is time - consuming and labor - intensive, and also has safety concerns, especially in the turbid - flowing and turbulent waters of the Brahmaputra during monsoons. This process involves making measurements at various sites, and this takes a considerable amount of manpower and resources.

Acoustic Doppler Current Profilers (ADCPs) offer a more sophisticated, efficient option. ADCPs take readings of water speed at different depths throughout the full water column without coming into contact with the water, and so they are non-invasive. They can produce both high-resolution flow profiles relatively quickly and can sample long sections of river within a limited period of time. For this reason, they are particularly well-suited to quantifying the complex and dynamic river flows surrounding Dibrugarh.

4. How Does ADCP, Based on the Doppler Principle, Work?

ADCPs operate based on the Doppler principle. They transmit sound waves into the water. When the sound waves travel through the water, they interact with particles that are moving, such as suspended matter, plankton, or small animals. When the signals bounce off of these flow particles, the returns' frequency changes according to the particles' relative velocity to the ADCP. By deciphering the change in frequency, the ADCP can establish the water's velocity at different depths, creating an overall picture of river flow. This enables accurate measurement of the flow rates, directions, and overall dynamics of rivers, providing valuable data for hydrological studies and water resource management.

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

To make high-quality river flow measurement using ADCP in Dibrugarh possible, there are certain equipment characteristics which should be of utmost importance. Material longevity is most vital. The ADCP should withstand the harsh river environment, e.g., exposing it to sediment-carrying water, strong currents, and changing water temperatures. High-quality, corrosion-resistant materials such as titanium or high - technology polymers make the equipment long-lasting and operate for a long time.

Size and weight are also of extreme importance. A lightweight and compact ADCP is more portable and convenient to deploy, especially with respect to the challenging river conditions near Dibrugarh. Such portability allows for greater flexibility in data acquisition from different parts of the river, including inaccessible parts.

Cost - effectiveness is another consideration. For large - scale or long - term monitoring programs in Dibrugarh, high - quality performance at a reasonable price of an ADCP would be sought after. This means that the river flow can be effectively monitored without costing too much, enabling routine and extensive observation of the behavior of the river.

6. Choosing the Right Current Measurement Equipment?

• *Methods of Deployment
• Mobile boat ADCP: Ideal for conducting surveys, measuring river discharges, and detailed mapping of flow. It is able to quickly cover extensive lengths of the Brahmaputra River near Dibrugarh, making it possible to survey data in different locations and gaining an understanding of the river flow pattern as a whole.
• Bottom - mounted (fixed) ADCP: Suitable for long - term continuous observation. Once installed on the river bed, it can receive information for extended durations, offering valuable information regarding long - term trends and trends in the river flow. This proves to be useful while investigating the ecological implications of water management practices and the effect of climate change on the river.
• Cableway ADCP: One can deploy a cableway ADCP in river reaches where a cableway exists. It is fixed above the river and can take the flow across the river at a location. This aids in making repeatable and precise measurements of flow at significant points within the river and can be used to validate and calibrate other measurement techniques.

Working Frequency

An ADCP's operating frequency determines its range and resolution. A 600 kHz ADCP with a 70 meter range can be used for relatively shallow sections of the Brahmaputra River or for taking high - resolution measurements in deeper reaches. A 300 kHz ADCP with a 110 meter range is more suitable for river sections that are deeper. The frequency to be employed is set by the unique characteristics of the river as well as the requirements of the measurements, e.g., the level of detail desired and the upper water column depth to be measured.

Brand Recommendations

World - leading ADCP brands include Teledyne RDI, Nortek, and SonTek, with high - quality products, advanced technology, and excellent reliability. For a cost - effective budget, ADCP manufacturer Chinese brand "China Sonar Panda ADCP" is also very good. Made of all-titanium alloy material, this "economy ADCP" is extremely durable and resistant to corrosion, well-suited to the harsh environment of the Soan River. Its high cost-effectiveness makes it within the budget of a range of users, from small-scale research projects in the vicinity to city-scale water management initiatives. To find out more, visit their website at https://china-sonar.com/.

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