Why We Measure River Flow in New Delhi?

1. Where is New Delhi?

Geographic Background

New Delhi, the capital of India, is located in the northern region of the country at about 28.61°N latitude and 77.21°E longitude. It is located in the Indo - Gangetic Plain, a vast region of gently sloping to flat land formed by thousands of years of deposition of alluvial sediments carried by the Ganges, Yamuna, and other rivers. The city enjoys a semi - arid climate with distinct seasons. Summers are extremely hot, and the temperature generally crosses 40°C during April to June. Winters, from November to February, are very cold with temperatures falling to 5 - 10°C. Monsoon, typically occurring between July and September, brings the majority of annual rainfall, though the amount varies significantly year to year.

Humanities and culture

New Delhi is culturally a cosmopolitan city and a city steeped in history. It has been a center of political power ever since, with a number of historic buildings that represent different phases of Indian history. The Red Fort, a world heritage property, was built in the 17th century by the Mughal Emperor Shah Jahan and is an example of the grandeur of the Mughal architecture. India Gate, war memorial, and the President of India's official residence, Rashtrapati Bhavan, are some of the other popular places. There are also markets like Chandni Chowk where one gets to witness the rich handicrafts of India, spices, and food culture. New Delhi is culturally rich, with numerous diverse forms of festivals round the clock, such as Diwali, Holi, and Eid, which depict the unity and diversity of the populace that inhabit the city.

Hydrology and River Overview

Yamuna River is the primary river system which has a prominent part in New Delhi. The Yamuna River arises from the Yamunotri Glacier in the Garhwal Himalayas and moves south - east across the foothills of the Himalayas prior to moving into the Indo - Gangetic Plain. The Yamuna River has a multifaceted but important role in New Delhi. It was formerly the largest supplier of freshwater in the city, used for domestic, irrigation, and industrial purposes. But over the years, due to rapid urbanization and industrialization and inappropriate disposal of wastes, the river is now highly polluted.

The current of the river is crucial to maintaining the environmental balance of the region. It supports a variety of aquatic organisms, although pollution has affected the ecosystem. For human use, while it is still utilized as a source of water for certain areas, water quality has become a significant issue. The river also has several tributaries, although in the New Delhi area, the focus is on the Yamuna itself. The merging of the river with other water bodies and its location within the regional water system render it a vital element to monitor and regulate.

2. How is the River Flow Near New Delhi?

Factors of Influence

Rainfall and Runoff

The flow of the river near New Delhi is significantly dependent upon the monsoon. Excessive monsoon rains in the catchments of the Yamuna River, including Himalayan catchments and northern plain catchments, during the monsoon season lead to high rises in river levels and flow velocities. However, the rainfall can be extremely erratic from year to year. During poor monsoon years, river flows decrease, leading to water shortages, especially since the city's water demand continues to rise. Urbanization has also affected the runoff properties. As more and more land becomes impervious cover like roads, buildings, and concrete structures, less rainwater can penetrate the soil, and the surface runoff happens quicker with a high likelihood of enhancing flooding during intense rainfall events.

Topography and River Morphology

The softly inclined surface of the Indo-Gangetic Plain upon which New Delhi is located results in a comparatively slow movement of rivers within the city itself. The width of the Yamuna River within New Delhi can vary, and in some places it has become narrower due to urban encroachment. Depth of the river also changes and the riverbed consists of a mixture of sand, silt, and clay. The bridges, embankments, and the man - made structures have, in turn, changed the natural river morphology and altered the pattern of flow and generated stagnation zones, which result in concentration of pollution.

Reservoir Operations

There are a few dams and reservoirs in the upper reaches of the Yamuna River, such as the Tehri Dam. These reservoirs are used for various purposes like generation of hydroelectric power, irrigation, and supply of water. They regulate downstream flow of the river by accumulating water during monsoon seasons and releasing water at a slow rate during dry seasons. However, the regimes of release from these reservoirs can also have extremely significant impacts on New Delhi river flow. Large-scale releases suddenly, for example, cause flooding in downstream reaches, while reduced releases during dry periods aggravate water shortages.

Historical Hydrological Events

There was a widespread flood in the Yamuna River in 2013 in New Delhi. Heavy monsoon rains upstream and the reduced capacity of the river because of encroachment and pollution-induced sedimentation led to the river overflowing. According to Delhi Disaster Management Authority reports, parts of low-lying areas around the river were inundated and displaced thousands. There were many such slum colonies near riverbanks that were severely affected, and roads and bridges were also damaged. Care must be taken to note such events because this will help in developing better flood - control structures, urban planning to avoid flood - prone areas, and improved water management for preventing floods and droughts.

3. How is the River Flow in New Delhi Observed?

Traditional Methods

Surface Drift Float Buoy Method

The surface drift float buoy method is a simple technique to measure river flow. A buoy is floated on the Yamuna River, and its travel over a certain distance and time is measured. The velocity of the buoy is then assumed as the surface velocity of the river. This is a ready-to-use technique with uncomplicated equipment but with limited applications. It only records the surface flow and not the variations in the velocity at various depths. Wind and other surface disturbances also influence the accuracy of measurement, particularly in the urban setting of New Delhi where there could be other pollutants and debris influencing the movement of the buoy.

Anchored Boat Method (Staff Gauge/Current Meter)

In the anchored boat method, a boat is fixed at a particular location in the river. A current speed is lowered into the water at different depths to take a reading of the speed, and a staff gauge is used to record the water level. It provides a high-resolution record of one point's speed but is time consuming, labor intensive, and dangerous, especially in a mucky and sometimes very rapid river like the Yamuna in New Delhi.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

Acoustic Doppler Current Profiler (ADCP) is a more efficient and modern method for river flow measurement in New Delhi. In comparison with traditional methods, ADCP can provide continuous velocity profiles from the bottom to the surface of the river non - invasively. It can quickly cover extensive tracts of the river, and this is significant to identify the complex patterns of flow in the Yamuna River, especially pertaining to pollution and urban- induced alterations. ADCPs are also secure in that they do not place workers close to the potentially dangerous river water.

4. How Does an ADCP Work Using the Doppler Principle?

An ADCP is a Doppler principle instrument. It emits sound pulses of a specific frequency. As these sound pulses propagate and encounter moving particles in the water, such as sediment or small organisms, the frequency of the backscattered sounds changes with the relative motion of the particles. If the particles are moving towards the ADCP, the frequency of the backscattered sound increases; if moving away, it decreases. By looking at these frequency changes, the ADCP can calculate the velocity of the water at different depths. The equipment typically includes a number of transducers that are tilted in different directions so that the instrument can measure the three-dimensional components of the velocity and accurately determine the net flow pattern of the river.

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

Equipment Requirements

Material Reliability

Because of the possibility of contamination and corrosive nature of water from Yamuna River in New Delhi, ADCP current meter gear needs to be designed with very durable material. Special metals that have resistance to corrosion like stainless steel or special alloys and resilient plastics need to be employed to ensure durability of the ADCP under such circumstances.

Small Size and Lightweight

New Delhi's riverbanks and the demand for simple installation in various points are in favor of using small and light ADCPs. They can be carried and shifted easily, either on a small boat or in areas with restricted access along the river.

Cost - Effectiveness

For real-time and extended-scale monitoring of the New Delhi Yamuna River, cost-effective ADCPs are crucial. Good-performing equipment available at reasonable prices allows more deployments to be made, which will offer extensive data collection for effective water management.

6. Selection of Right Current Measurement Equipment

Deployment Methods

Boat-Mounted (Moving Boat) ADCP

A boat - mounted ADCP flow meter would be most suitable to conduct surveys of the Yamuna River in New Delhi. It is capable of quickly measuring the discharge and surveying the flow features across the width of the river, which is extremely beneficial in understanding the general water flow as well as for flood - monitoring and pollution - assessment.

Bottom - Mounted (Fixed) ADCP

To monitor the river flow continuously in the long term, an ADCP can be fixed bottom - mounted on the riverbed. This gives significant information regarding the long - term trends in river flow, which is crucial for water resource management and ecological studies in New Delhi.

Cableway ADCP

In certain parts of the Yamuna River where cableways exist, one can utilize a cableway ADCP. This is ideal in areas where boat deployment is not possible or where fixed - bottom installation cannot be done, making exact flow measurements possible.

Working Frequency

For the Yamuna River of New Delhi, a 600 kHz ADCP is usually a good option because it has a good compromise between range (up to 70 meters horizontally) and resolution, which in turn is sufficient to measure the flow in the relatively wide and shallow parts of the river. A 300 kHz ADCP, having a longer range of up to 110 meters, can be used for wider or deeper parts of the river but with inferior resolution.

Brand Recommendations

Reliable and high-quality ADCP brands by world-renowned companies such as Teledyne RDI, Nortek, and SonTek are extremely popular. Amongst Chinese brands,the ADCP supplier’s "China Sonar Panda ADCP" is an excellent value-for-money brand. As it's an all-titanium alloy structure, it's extremely durable and corrosion-resistant, and therefore a suitable option for Yamuna River's tough environment in New Delhi. It is also highly cost-effective, so it is affordable for different monitoring projects. To learn more, you can check their website at https://china-sonar.com/.

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