Why Do We Measure River Flow in Delhi?

1. Where is Delhi?

Geographical Background

Delhi is a union territory in the northern part of India, situated at approximately 28.61°N latitude and 77.21°E longitude. It is a peculiarly situated city, surrounded by the states of Haryana on three sides and Uttar Pradesh in the east. Delhi lies in the Indo - Gangetic Plain, and it is characterized by the flat landscape formed by the centuries-old accumulation of alluvial deposits by the rivers. The flat landscape has been conducive to city expansion but means that Delhi is prone to the consequences of river flows, especially instances of heavy rainfall. The location of the city places it in a region that experiences a monsoon-dominated climate, an influence that affects the water bodies that are inside and around it.

Humanities and culture

Delhi is also culturally rich, with a long history of heritage that goes many centuries back. Delhi has been the capital of various empires like the Mughals and the British, leaving behind a heritage of majestic structures. Legendarily built structures such as the Red Fort by Mughal Emperor Shah Jahan and Qutub Minar, a World Heritage Site, demonstrate the architectural prowess of times past. Art, music, and literature thrive in the city as well, with the traditional forms of qawwali music and Urdu poetry existing alongside modern-day cultural movements.

Delhi's culture is a vibrant mix of traditions from across India. Festivals like Diwali, Eid - ul - Fitr, and Christmas are celebrated with great enthusiasm, which is a sign of religious diversity and unity of the city. Street foods of the city like chaat, parathas, and kebabs are loved by natives as well as visitors. The crowded bazaars of Delhi, including Chandni Chowk, give one a feel for the city's vibrant cultural past, with vendors selling handicrafts, textiles, and jewelry in the traditional style.

Hydrology and River Overview

Yamuna River is the largest body of water in Delhi. It begins at the Yamunotri Glacier in the Himalayas and runs south through the state of Uttarakhand before entering Delhi. Yamuna River is the largest water body in Delhi and serves a crucial function in water supply, ecosystem, and overall health of the city. However, the river has been grappling with serious pollution problems due to urbanization and industrialization over the decades.

Despite being polluted, the Yamuna remains a vital source of water for Delhi. Most of the city's household, industrial, and agricultural water requirements are being met from the river, albeit after being thoroughly treated before supply. The river also has a fragile ecosystem, with certain species of fish, birds, and other aquatic creatures struggling to survive in the polluted water. In addition, the floodplains of Yamuna in Delhi act as a natural shield during rainy seasons, absorbing surplus water and reducing the risk of flooding in the city.

2. What is the River Flow Around Delhi?

Factors Affecting

Rainfall and Runoff

Delhi is a semi-arid region with a monsoon season extending from June to September. During these months, the city receives the bulk of the annual rainfall, which typically accounts for 75 - 80% of the total rainfall. Excess runoff is caused by heavy monsoon rains, leading to the flooding of the Yamuna River. Rainfall intensity and duration can vary significantly from year to year and thus lead to random changes of river flows. On the other hand, the dry season between October and May witnesses a steep decline in the river flows, and water levels go down, sometimes leading to water scarcity in the city.

Topography and River Morphology

The flat character of the Indo - Gangetic Plain on which Delhi stands causes the Yamuna River to flow comparatively slowly, with a low slope. The slow flow allows sediment to settle on the river bed and banks over time. The width of the river in Delhi varies from section to section, some sections of it being wider and others being narrower. The meandering character of the river in the city also has its impact on the current, the outer bends having quicker - flowing water that brings erosion and inner bends having slower - flowing water that leads to sedimentation. Bridges, embankments, and other man-made features in Delhi also change the natural flow patterns of the river as it originally existed.

Reservoir Operations

Several dams and barrages constructed on the Yamuna River upstream of Delhi, such as Hathnikund Barrage in the Haryana state, are used for water storage, irrigation, and generation of power. The release of water from these reservoirs is highly regulated such that a steady supply of water to Delhi and other downstream areas is ensured. However, changes in dam operation, especially during years of low rainfall or high water use, have the ability to significantly change the river flows in Delhi. Low water releases have the potential to exacerbate water shortages and environmental conditions in the city.

Historical Hydrological Events

Delhi has experienced numerous floods and water - related problems over the years. There were heavy monsoon rains in 2013, which resulted in extensive flooding in parts of Delhi as the Yamuna River overflowed its banks. The floods, according to the Delhi Disaster Management Authority, affected thousands of people, displaced families, and caused extensive damage to infrastructure, including roads, bridges, and buildings. Alternatively, drought-like conditions also occurred in years with below-average rainfall, inhibiting water supply for domestic, industrial, and agricultural use. Ongoing monitoring of these events is required to create effective flood-control as well as water-management practices in Delhi.

3. How is the River Flow in Delhi Monitored?

Traditional Methods

Surface Drift Float Method

The surface drift float method is a simple method of measuring river discharge. It was done by floating a device, such as a buoy or wood, on the river surface in order to measure the surface velocity of the river. The length of time that it covers a calculated distance is used in measuring the surface velocity of the river by dividing the distance by the duration. But with this method, information on only surface flow is achieved, and variables like wind can be fed into the reading and provide a deceptive measure of velocity.

Anchored Boat Method (Staff Gauge / Current Meter)

With the anchored boat method, an anchored boat is moored at a station in the river. A current meter is then lowered at various depths in the river to measure the velocity of water, and a staff gauge is used to measure the water level. Measuring some velocities at different locations of the cross - section of the river and finding the cross - sectional area, the river discharge can be computed. This method yields more accurate information but is time - consuming, labor - intensive, and hazardous to safety, especially in a busy city river like the Yamuna River in Delhi.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

The Acoustic Doppler Current Profiler (ADCP) is a better and affordable technology to estimate river flow. Non - invasive by nature, the ADCP employs the use of sound speed to calculate water speed at different depths. ADCP can capture continuous profiles of the river flow from the surface to the bed in a short time and is hence perfectly apt for the observation of the variable and complex river flows of Delhi. It enables more precise and elaborate data collection, which forms an integral part of effective water resource management in the city.

4. How Does ADCP Apply the Doppler Principle?

An ADCP current meter operates based on the Doppler effect principle. It emits sound waves at a specified frequency into the water. When the sound waves encounter moving particles in the water such as sediment, plankton, or water molecules, the frequency of the returned waves is altered. The frequency of the returned waves is higher if the particles are moving towards the ADCP and lower if moving away. By precisely measuring this frequency change (Doppler shift), the ADCP can calculate water velocity at different depths. Multiple transducers on the ADCP are utilized to measure velocity in different directions, and by utilizing these measurements, one can ascertain the three-dimensional flow structure of the river.

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

Equipment Requirements

For reliable ADCP measurements in the Yamuna River, Delhi, some equipment attributes are critical. In the case of the polluted and quite often - demanding river conditions, material durability is paramount. ADCPs constructed with corrosion - resistant materials such as stainless steel or titanium are desirable to guarantee long - term operation. A compact and light-weight design will also be useful, since it will be easy to transport and deploy, particularly in the urban setting of Delhi. Cost-effectiveness is also vital, since it will facilitate adoption of the technology at a large scale for holistic monitoring of the river flow.

6. How to Select Appropriate Current Measurement Equipment?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: Best suited to conduct large - scale river surveys, quantifying discharge over extensive reaches, and quickly mapping flow patterns. It can gauge wide sections of the Yamuna River in Delhi as the boat is relocated, providing an overview of the flow conditions.
• Bottom - Mounted (Fixed) ADCP: Of suitable use in long - term continuous observation, a bottom - mounted ADCP can be positioned fixed at the riverbed for obtaining data over long time periods. This offers insight into long - term trends of flow, seasonal variability, and impacts of numerous factors on the river flow.
• Cable - Way ADCP: In cable - way provisioned river reaches, a cable - way ADCP can be suspended and cross the river to take measurement at multiple points. It is beneficial where boat - based measurements may be problematic with heavy traffic or other restritions in the urban river.

Working Frequency

• 600 kHz ADCP: A 600 kHz ADCP offers a good trade-off between range and resolution and can take measurements with a maximum horizontal range of 70 meters. It would be useful in most river reaches in Delhi to accurately measure the flow characteristics.
• 300 kHz ADCP: With increased range up to 110 meters, a 300 kHz ADCP will be ideal for deeper and wider sections of the Yamuna River in Delhi.

Recommended Brands

Popular worldwide ADCP flow meter manufacturers are Teledyne RDI, Nortek, and SonTek, known for their high - quality, dependable instruments employed in numerous hydrological studies and monitoring campaigns. As a budget-friendly alternative, the ADCP supplier Chinese brand’s "China Sonar Panda ADCP" is a great option. Made from all-titanium alloy, it boasts better durability and reliability, making it more than capable of withstanding the rigorous river condition in and around Jammu. As an "affordable ADCP", it provides high-class performance at a low cost. Find out more at https://china-sonar.com/.

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