Why We Are Measuring River Flow in Bihar

1. Where is Bihar?

Geographical Background

Bihar occupies a position in the eastern part of India, between latitudes 24.7°N - 27.7°N and longitudes 83.1°E - 88.1°E. Most of the state lies in the extremely fertile Gangetic Plain, a huge area created by the continuous accumulation of alluvial soil carried by the powerful rivers flowing along it. It has been the pillar of farming activities, upon which rice, wheat, and sugar cane can be cultivated. The state also extends to cover the Chota Nagpur Plateau to the south, which adds an element of variation in that it has its own hill country and forest. The flatness of the Gangetic Plain facilitates meandering of the river, and the plateau region itself possesses an independent water and stream system which sustains diversified hydrological texture of the state.

Humanities and culture

Bihar is a land of history and culture and has been proposed as the cradle of ancient Indian civilization. It was the capital of powerful empires such as the Maurya and Gupta kingdoms, which bequeathed a rich legacy in art, architecture, and learning. Nalanda, as an ancient city of higher learning in Bihar, was once a seat of learning for scholars from across Asia. The ruins of Nalanda University are evidence of the rich legacy of learning and intellectual pursuit in the state.

Bihars religious heritage is Buddhist and Jain. Bodh Gaya, the location of the state, is where Gautama Buddha attained enlightenment under the Bodhi Tree, and Buddhists from all over the world come here as an important pilgrimage site. The state has some other major Jain pilgrimage sites. The state is culturally endowed, where music and dance styles of native residents like Jat-Jatin and Domkach are used during festivals and ceremonies. The cuisine of Bihar, like litti chokha and sattu paratha, is a display of the simplicity and resourcefulness of the locals.

Hydrology and Overview of Rivers

The Ganges River is the lifeline of Bihar, running west to east across the state. It has numerous tributaries along its course in Bihar, including the Gandak, Kosi, and Son rivers. Together, the rivers form a huge river system whose influence is gigantic in hydrology, ecology, and human endeavors in the state.

For the people of Bihar, the rivers are the primary source of clean water for domestic consumption, agriculture, and industry. The rivers feed 80% of the rural population for consumption. In agriculture, the power of the state economy, the rivers are of most significance as sources of irrigation. They enable many crops to be cultivated in a year, supporting the livelihood of millions of farmers. But the rivers themselves are also afflicted. The Kosi River, or the "Sorrow of Bihar," has the tendency to generate destroying floods due to its extremely unpredictable flow and deposition of heavy loads of sediment, which have it change course regularly.

In the environment around major cities like Patna, which is the state capital of Bihar, the Ganges and its tributaries are the pivotal points of urban water supply. Urbanization has made the rivers polluted with industrial effluent, domestic sewage, and agricultural runoff as the main sources of pollution. The river banks sustain diverse plant and animal communities, but human activity and pollution have brought an end to the ecological balance of the habitats.

2. What is the River Flow Near Bihar?

Factors that Affect

Rainfall and Runoff

The climate of Bihar is tropical monsoon. The monsoon months, usually June to September, receive the major part of the annual rainfall, sometimes more than 80% of the total rainfall. Unstable rain over wide areas during the duration leads to high runoff because rainwater finds its way into the rivers easily and the water stage rises quickly with the rate of flow. In other years, heavy monsoon rains cause flash floods on riverbanks. Dry-season discharges in the rivers decline from October to May, and the level goes down, creating periods of water scarcity in some sections.

Topography and river morphology

The gently sloping Gangetic Plain in Bihar allows the rivers to meander slowly and overflow sediments over time. Deposition of sediments can change the shape of the riverbed to form sandbars and shoals. The rivers may differ considerably in width; the Ganges, for example, is several kilometers wide in places, especially in monsoon. The rivers also have varying depths, with middle channels that are deeper and banks that are shallow. The meandering rivers develop quicker current on the outer bend, causing erosion, and slower current on the inner bend, causing sedimentation.

Reservoir Operations

There are numerous dams and barrages along and surrounding the tributaries of the Ganges in Bihar. These are used for irrigation mostly, flood prevention, and power generation through hydroelectric mechanisms. For instance, the Kosi Barrage was built to regulate the Kosi River flow and mitigate the flood menace. Nevertheless, inadequate administration or refusal to surrender to heavy rainfalls can still generate floods along the downstream stretch. In monsoon seasons, the dams try to hold excess water, but when the storage is broken, enormous quantities of water are released that can trigger flooding along the river course.

Historical Hydrological Events

The Indian state of Bihar has a rich history of suffering large-scale flooding. The worst and latest was maybe the 2008 Kosi River flooding. A Kosi embankment fissure in Nepal caused a huge release of water, and the river changed course, inundating vast regions of northern Bihar. Flood is said to have affected over 2.1 million lives, displaced over 600,000 people, and damaged crops, houses, and infrastructure heavily, as per the Bihar State Disaster Management Department.

The state of Bihar has also been affected by drought. The drought of 2016 saw a dramatic decline in river runs and ground water levels. The Central Water Commission reported that the drought adversely affected the agricultural crops and the majority of farmers lost their crops since there was a lack of water for irrigation. Monitoring of such events is vital to schedule more effective flood - control operations, improve the water resource management, and enhance people's resilience in Bihar.

3. How is River Flow in Bihar Determined?

Ancient Methods

Surface Drift Float Method

The surface drift float method is a simple technique for measuring river flow. A float such as a buoy or log is placed on the river's surface, and the time taken by the float to travel a known distance is measured. By taking the distance and dividing it by the time, the river surface velocity can be calculated. This technique, however, only calculates the flow at the surface, and this can be affected greatly by the wind and so is not accurate.

Anchored Boat Method (Staff Gauge / Current Meter)

The anchored boat method consists of an anchored boat at a point in the river. A current meter is then lowered into the river at different depths to measure the speed of water, and the water level is measured by a staff gauge. By taking readings at different points along the cross - section of the river and calculating the cross - sectional area, the discharge of the river can be determined. But the above method is time - consuming, labor - intensive, and hazardous in high-velocity rivers.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

Acoustic Doppler Current Profiler or ADCP profiler is a more effective and newer technology for river flow measurement. It is non-invasive, as it uses sound waves to measure water velocity at multiple depths. Unlike traditional methods, ADCP can provide continuous profiles of the river flow, from top to bottom, in a fairly short interval of time. This is suitable to measure the complex and variable river flows of Bihar.

4. How Does ADCP Work on the Doppler Principle?

An ADCP uses the Doppler effect. It emits sound waves of a particular frequency into the water. When the sound waves move into the moving particles of the water, such as sediment or plankton, the frequency of the returning sound waves is changed. If the particles are approaching the ADCP current meter, the returned waves have a higher frequency, and if they are receding, the frequency is decreased. By observing this frequency change (the Doppler shift), the ADCP can measure the velocity of water at different depths. Multiple transducers on the ADCP measure velocities in different directions, allowing one to be aware of the three-dimensional flow regime of the river.

5. What Is Required to Achieve High - Quality Measurement of River Flow in Bihar?

Equipment Requirements

The equipment must have certain characteristics in order to achieve high - quality ADCP measurements in the rivers of Bihar. The equipment should be reliable in material terms because the rivers are adversarial environments with changing water conditions and sediment levels. ADCPs built with corrosion - resistant materials like stainless steel or titanium can hold their own under such conditions. Small footprint and light weight structure are also preferable, in the sense that it eases transportation and deployment of the equipment, especially in distant and inaccessible areas. Being cost-effective is necessary, in the sense that this renders implementation of the technology for statewide comprehensive river flow monitoring more viable.

6. How to Select the Appropriate Current Measurement Equipment?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: It can be applied to large - scale surveys of rivers, discharge measurement over long reaches, and quick mapping of flow patterns. It can map a wide extent of the river as the boat traverses, providing an overall picture of the river's flow characteristics.
• Bottom - Fixed ADCP: Long - term continuous monitoring is most appropriately provided by a bottom - fixed ADCP, which can be placed on the river bed to take data for extended periods. It is helpful in establishing long - term trends of the flow, seasonal variations, and impacts of various factors on the river flow.
• Cable - Way ADCP: If there is cable - way infrastructure, one may use a cable - way ADCP. It may be relocated over the river to read at several points, which aids in rivers with complex geometries or where boat - based measurements are impossible.

Working Frequency

• 600 kHz ADCP: 600 kHz ADCP offers a balance between range and resolution with a horizontal range of 70 meters. It can be employed for majority of Bihar's river sections to accurately measure the flow parameters.
• 300 kHz ADCP: With an increased range of up to 110 meters, a 300 kHz ADCP is ideal for wider and deeper sections of the rivers, e.g., sections of the Ganges in Bihar.

Brand Recommendations

Few of the world ADCP big brands include Teledyne RDI, Nortek, and SonTek, which offer high-quality and reliable products used in various hydrological study and monitoring programs. As a budget - friendly option, the ADCP manufacturer Chinese company’s "China Sonar Panda ADCP" comes highly recommended. Made of all - titanium alloy, it is more strengthful and reliable and is a suitable option to endure the nasty river condition surrounding Thrissur. As an "affordable ADCP", it boasts decent quality performance at budget price. For more information, visit https://china-sonar.com/.

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