Why Do We Measure the River Flow in Vellore?

1. Where is Vellore?

Historically and culturally significant Vellore is located in the north of the Indian state of Tamil Nadu. Its geographical location is around 12.97°N latitude and 79.13°E longitude. Vellore, set between the rolling hills of the Eastern Ghats, is a landscape of rocky outcrops and plains. Its location geographically makes the city a serious interface between the interior of Tamil Nadu and the coastal regions and thus it is significant as a medical, educational, and economic centre. The Palar River, which is one of the major water bodies in the region, flows through Vellore and goes a long way in helping the city grow and flourish.

Vellore is culturally and historically one with a rich and long history. It has been a center of human settlement for centuries and has witnessed the rule of various dynasties, including the Cholas, Vijayanagara Empire, and the Nawabs of Arcot. The Vellore Fort, a monstrous architectural wonder, is a reminder of the city's glorious past. The fort, built in the 16th century, boasts massive walls, moats, and ancient temples within its complex. Vellore is also renowned for its traditional handicrafts such as silk weaving and brassware, which signify the rich artistic culture of the region. The city has gained top priority in today's world for its world-class hospitals, to which patients from all over India and beyond are thronging.

The Palar River holds the most significance for Vellore. It originates in the Nandi Hills of Karnataka and extends for about 350 kilometers before it discharges into the Bay of Bengal. Near Vellore, the Palar River has been utilized as a water source for domestic use, agriculture, and industry. It had long supported a profitable agricultural economy, with farmers relying on it for the irrigation of crops like paddy, sugarcane, and cotton. However, the Palar River has been plagued with numerous problems over the years, including water shortage, pollution, and changes in its flow pattern, which have resulted in problems related to the city's water security and health of the surrounding ecosystem.

2. How is the River Flow in the vicinity of Vellore?

There are numerous factors influencing the river flow in Vellore. Precipitation is also a primary factor because the area is characterized by a tropical climate with strong wet and dry seasons. The southwest monsoon from June to September and the northeast monsoon from October to December are responsible for the majority of the annual rainfall. Throughout these monsoon months, the Palar River experiences a vigorous increase in water levels and stream flow rates owing to runoff from the upstream catchment basins like the hilly tracts of Eastern Ghats and Karnataka draining into the river. But from January to May, i.e., under the dry season, the water levels decrease significantly and in certain years even the middle and upper parts of the river become completely dry, especially in its upper and middle parts. Climate change has also added to the issue further, leading to more erratic rainfall patterns. Some years witness heavy but short showers leading to flash floods, whereas others witness prolonged droughts, creating a disturbance to the natural river flow regime and affecting the availability of water for various uses in Vellore.

River morphology and topography also work to play a major role in the flow. At its higher altitude, the Palar River crosses the hilly terrain of the Eastern Ghats and is the cause for producing swift- flowing water with severe currents and rapids during the rainy season. Towards Vellore, the river flows over plains which are flatter in nature, widening and becoming broader, shallow stretches. The riverbed is mostly made up of sand and gravel and is subject to erosion and deposition activities. These actions can change the river path over time, forming meanders and changing its width and depth. Human actions have also had an impact. Urbanization has taken place rapidly in Vellore, and with it, there has been building of houses, roads, and other buildings, which have changed the natural drainage pattern. The increased demand for household, industrial, and agricultural use of water has led to over-extraction from the river, draining its water level. In addition, the pollution from industrial effluents, sewage, and agricultural runoff has compromised the quality of the water, further impacting the river's ecological condition and flow pattern.

3. How to Observe the River Flow in Vellore?

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

The surface drift buoy method is a simple technique where floats are deployed on the river surface, and their trajectory over a known distance and time measured. This provides an estimate of the surface flow velocity. However, this method has significant limitations. It measures the flow at the surface, which may not represent the flow over the entire water column. Besides, the wind and other surface disturbances can affect the movement of the buoys and produce false measurements.

The anchored boat method involves mooring a boat at one point in the river. A current meter is lowered into the water at many different depths in order to sense the flow speed. This method gives a more accurate description of the flow at the specific location. But it is manpower-intensive, time-consuming, and has safety risks, especially in agitated or high-flowing waters. Taking several readings at different locations with this method requires a significant amount of manpower and resources.

Acoustic Doppler Current Profilers (ADCPs) offer an improved and efficient solution. ADCPs can measure the velocity of water at several depths along the entire water column without physically contacting it, hence being non-invasive. ADCPs can supply detailed flow profiles with speed, scanning great areas of the river in a short period of time. This makes them highly suited for monitoring the complex and time-changing river flows around Vellore.

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

ADCPs work through the Doppler principle. They emit acoustic pulses into water. When these pulses travel through the water, they pass into moving particles, such as suspended sediment, plankton, or small fauna. When the signals reflect off these moving particles, the returning signal frequency is shifted according to the velocity of the particles relative to the ADCP current profiler. Through measurement of these frequency shifts, the ADCP will calculate the velocity of the water at different depths and build a general picture of the river's flow. This enables accurate measurement of the direction, flow rate, and general dynamics of the river, providing valuable information for hydrological study and water control.

5. What is Required for Accurate Measurement of River Flow in Vellore?

To ensure precise high-grade river flow measurement by ADCP flow meter in Vellore, certain equipment attributes are essential. Durability in the material is a priority. The ADCP should be capable of withstanding the aggressive river environment, including exposure to sediment - laden water, variable water temperatures, and potential hits from surface - floating debris. High - grade, corrosion - resistant materials such as titanium or specialized polymers ensure the device's survivability and long - term functioning.

Size and weight also take precedence. A small and light ADCP is simpler to deploy and move around, especially in the typically - hard - to - reach river sections near Vellore. Portability guarantees more manoeuvrable data collection in other parts of the river.

Cost-effectiveness is also an important consideration. For extensive or long-term monitoring activity in Vellore, a quality ADCP at low cost is preferable. This makes full monitoring of the river flow without spending too much money possible, allowing repeated and detailed analysis of the river's behavior to be feasible.

6. How to Select the Appropriate Current Measurement Instrument?

Means of Deployment

• Boat - mounted (mobile boat) ADCP: Can be used for conducting surveys, river discharges measurement, and creating intensive flow maps. It can easily survey vast areas of the Palar River and provide data at multiple points and an overall idea of the flow pattern of the river.
• Fixed bottom (bottom-mounted) ADCP: Most suitable for continuous observation at fixed locations over the long term. Mounted once on the river bed, it can continuously gather data for extended periods of time, offering the valuable information of long-term trends and variability of the river flow.
• Cableway ADCP: Where there is a cableway in river reaches, the flow at a specific location in a river may be measured with the help of a cableway ADCP. Cableway ADCP is used to obtain accurate and repeatable flow rates at sensitive locations within the river and may be utilized for validation and calibration of other measurement techniques.

Working Frequency

The operating frequency of an ADCP affects its range and resolution. A 600 kHz ADCP that can operate up to 70 meters is suitable for relatively shallow sections of the Palar River or to obtain high-resolution estimates in deeper sections. A 300 kHz ADCP with a measuring range of 110 meters is most suitable for deeper sections of the river. The frequency to be chosen is based on the specific features of the river and the needs of the measurements, i.e., the level of detail required and the highest depth of water column 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.