Why Do We Measure the Tezpur River Flow?

1. Where is Tezpur?

Tezpur, a picturesque city in the Indian state of Assam, is a significant location in the northeast of India. It lies geographically close to 26.68°N latitude and 92.78°E longitude. Located on the southern banks of the Brahmaputra River, Tezpur is surrounded by a lush and green terrain, comprising the fertile plains of the Brahmaputra Valley. As it is located at the base of the Himalayas, the city enjoys a unique mix of hilly and plain topographies, not just rendering it a beautiful place but also an area of diverse ecological and geographical features.

Culturally and historically, Tezpur is full of indigenous traditions. It has been a melting pot of various ethnic communities like the Assamese, Bodo, and other aboriginal tribes. The cultural heritage of the city is alive in its handicrafts, music, dance, and festivals. Bihu, the most colorful festival of the state in Assam, is observed in Tezpur with much enthusiasm, comprising vibrant folk dances, traditional music, and trendy dresses. Historically, Tezpur has witnessed the rise and fall of different dynasties. It was an important center during the Ahom Kingdom era, and remnants of that time still exist in the form of ancient temples, forts, and historical buildings. The city is also a part of Indian mythology. Tezpur is believed to have been the site of a grand battle between devas and asura gods, giving its historical past a supernatural sheen.

Brahmaputra River, described as one of the major rivers in Asia, is the lifeline of Tezpur. It starts flowing from the Chemayungdung Glacier of Tibet, China, as the Yarlung Tsangpo River, flowing east and then making a sharp turn to flow into India through Arunachal Pradesh and then it is named the Brahmaputra. The Brahmaputra is multi-dimensional in character within Tezpur. It is a vital source of water that is domestically consumed, utilized in agriculture, and for industries. Historically, the river was a valuable trade route, facilitating the transportation of products such as tea, wood, and spices, which led to immense economic growth in the city. The river also sustains a rich and varied fauna that holds a range of fish species, bird species, and aquatic vegetation. However, the unpredictable nature of the Brahmaputra, especially during monsoon, forms a constant threat of flood towards Tezpur and surrounding regions.

2. How is the River Flow around Tezpur?

Multiple parameters influence the river flow around Tezpur. The prime factors are runoff and precipitation. The region experiences a tropical monsoon climate, and the monsoon period typically extends from June to September. During this time, heavy and consistent rainfall within the upper catchment basins within the Himalayas and the surrounding hilly regions occurs. The rain runoff causes a significant increase in the level and speed of water of the Brahmaputra River. The water level rises and water velocity increases noticeably as the river approaches Tezpur, with water volume increasing and current becoming stronger, even posing a threat of causing floods. In contrast to this, between October and May, which is the season of dryness, water levels drop significantly, and the flow becomes immensely reduced. Climate change has also complicated the scenario with more volatile monsoon trends, with heavier downpours in a shorter duration and extended dry spells, leading to more intense and frequent occurrences of flood and drought within the area.

The geography and river morphology also significantly impact the flow. The Brahmaputra River at Tezpur flows through expansive, shallow floodplains, which allow the river to disperse. The sand and sediment composing the channel bed continuously erode and deposit. This makes the river change direction over time and thus create oxbow lakes and meanders. Tributary contribution, such as the Jia Bharali River that joins the Brahmaputra at Tezpur, impacts the flow dynamics as well. The tributaries help add volume to the water and potentially alter the direction and speed of the primary river flow, and therefore, the complex hydrological status of the region.

The tributaries of the Brahmaputra have dams and barrages upstream that are utilized primarily for flood control, the generation of hydropower, and irrigation. While the facilities help regulate the flow of water, operation can result in different impacts on Tezpur. Uncontrolled water release or unexpected heavy rains upstream can cause an unexpected elevation of water levels and inundate Tezpur. On the other hand, in the summer season, reduced water release can affect the city's supply of water for various uses.

3. Measurement of the River Flow in Tezpur?

There are a few ancient techniques to measure the river flow like the anchored boat method and the surface drift buoy method.

The surface drift buoy method is a simple one. Floats are dropped on the surface of the river and their travel over a known length of distance in a specific time is recorded. This provides an estimate of the surface flow velocity. However, this method has a number of disadvantages. It only measures the flow at the surface, and the flow at the surface is not necessarily representative of the flow throughout the water column. Wind and other surface - level disturbances also have a drastic effect on the movement of the buoys and therefore yield erroneous measurements.

The anchored boat method involves anchoring the boat at a stationary point within the river. A current meter is subsequently released into the water at various depths to measure the flow velocity. This method gives a more accurate profile of the flow at the point. It is, however, time - consuming, labor - intensive, and dangerous, especially in the monsoon's turbid and fast - flowing waters of the Brahmaputra. There is a significant amount of manpower and resource required for taking measurements at numerous points using this method.

Acoustic Doppler Current Profilers (ADCPs) offer a sophisticated and more cost-effective solution. ADCPs can be used to measure water velocity at multiple depths throughout the entire water column without physical contact, so they are non-invasive. ADCPs can quickly derive accurate flow profiles across broad areas of the river in a short time. They are thus extremely appropriate for monitoring the complicated and dynamic river flows near Tezpur.

4. How Does ADCP, Which Uses the Doppler Principle, Work?

ADCPs work on the Doppler principle. They transmit acoustic signals into water. While passing in the water, they are caught by flowing particles, such as suspended sediment, plankton, or small organisms. As the signals are returned by these traveling particles, the frequency of the return signals differs according to the velocity of the particles with respect to the ADCP. From the measurement of these frequency variations, the ADCP can infer the water velocity at different depths, and it gives a comprehensive profile of the river flow. This provides accurate measurement of flow rates, directions, and the overall river dynamics, providing valuable data for water management and hydrological study.

5. What is Needed for High - Quality Measurement of River Flow in Tezpur?

For precise high-quality measurement of river flow by ADCP at Tezpur, equipment requirements exist. Robustness of material is the most essential characteristic. The ADCP should be capable to resist the harsh river environment, including exposure to sediment-carrying water, high currents, and changing water temperature. High-grade corrosion-proof material such as titanium or advanced polymers ensures dependability in the device as well as its long-term functionality.

Size and weight do also matter. A light and miniature ADCP is simpler to transport and instal, especially considering the challenging river conditions at Tezpur. Its portability allows data collection to be conducted on more flexible terms at different stretches of the river, including hard - to - reach areas.

Cost effectiveness is a consideration too. A high-performance ADCP in a reasonable price range is the best for long-term or large-scale monitoring work in Tezpur. The end-to-end monitoring of the river flow can be done without breaking the bank, permitting routine and detailed examination of the river's behavior.

6. How to Select the Appropriate Current Measurement Equipment?

Deployment Methods

• Boat-mounted (mobile boat) ADCP: Ideally placed to conduct surveys, measure river discharge, and produce high-resolution flow maps. It can conduct large sections of the Brahmaputra River near Tezpur at short notice, and multiple positions can be sampled and compared to provide a big picture of the flow patterns of the river.
• Bottom-mounted (fixed) ADCP: Suitable for long-term ongoing monitoring. Once it is fixed on the riverbed, it can collect data for a long time, giving valuable data about long-term changes and fluctuations in the river flow. It is helpful to study the ecological impacts of water management practices and the impact of climate change on the river.
• Cableway ADCP: If there is a cableway in the river sections, there is the possibility of using a cableway ADCP. It is suspended over the river and has the capability of measuring flow over the river at a single point. The benefit in this case is that it can give dependable and repeatable flow measurements at strategic points in the river, which can be used for calibration and validation of other measurement techniques.

Working Frequency

Operating frequency of an ADCP decides its range and resolution. One 600 kHz ADCP with a range of 70 meters is suitable for relatively shallow sections of the Brahmaputra River or to obtain high-resolution observations in deep sections. One 300 kHz ADCP with a measuring range of 110 meters is suitable for deeper sections of the river. The frequency used is determined by the inherent characteristics of the river and the needs of the measurements, such as the level of detail needed and the upper limit of the water column depth to be measured.

Brand Recommendations

The world - recognized ADCP brands include Teledyne RDI, Nortek, and SonTek. They deal with high - end ADCPs with advanced technology and proven reliability. For an affordable choice, the Chinese brand "China Sonar Panda ADCP" is suggested. This "economy ADCP," made of all - titanium alloy material, is resistant and long - lasting in Multan's harsh river environment. It is low - cost - effective, and a well - suited choice for local research projects to city - wide water management projects. To learn more, visit their website at https://china-sonar.com/.

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