Why Do We Monitor River Flow in Karnataka?

1. Where is Karnataka?

Geographic Background

Karnataka is located in the southwestern part of India, between approximately 11.5°N - 18.5°N latitude and 74°E - 78.5°E longitude. The state possesses a diverse geographic landscape. The Western Ghats make up its western boundary, a coastal parallel mountain range that is a critical region of ecological catchment, giving rise to the high level of biodiversity and numerous rivers. Karnataka possesses a long Arabian Sea coastline composed of sandy shores, while the interior features plateaus as well as plains. The state has a tropical climate, and between March and May it has hot summers with a maximum of as high as 40°C. Between June and September, the state receives the southwest monsoon, which supplies the majority of the rains to the state's yearly water supply, and therefore notably fills up the water resources of the state, while the northeast monsoon has a relatively lesser impact.

Humanities and culture

Karnataka has an ancient and rich culture that goes thousands of years back. It is renowned for its beautiful historic monuments, such as the UNESCO - World - Heritage - site Hampi ruins. The Hampi ruins were the capital of the Vijayanagara Empire and have a vast number of temples, palaces, and other structures showcasing the opulence of the past. The state is also a hub of traditional crafts and art. Yakshagana, a traditional theatre form, is a combination of dance, music, and drama to depict mythological and historical stories. Karnataka is famous for silk manufacturing, especially in states like Mysore, where the Mysore silk sarees are greatly prized due to their excellence and craftsmanship. The state celebrates numerous festivals in its zest, like the Ugadi and Kannada New Year, and Dasara at Mysore, renowned for its pageantry and cultural displays.

Hydrology and River Overview

Krishna and Cauvery are the two major river systems of Karnataka. The Cauvery River originates in the Brahmagiri Hills of the Western Ghats and passes through the southern part of the state and is generally referred to as the "life-giving river." It is a significant source of water for domestic, agricultural, and industrial uses that sustains the cultivation of crops like paddy, sugarcane, and coffee in the rich Cauvery basin. Krishna flows in the northern part of Karnataka, as is not the case with the Bhima River. It is created in Maharashtra and flows through Karnataka before it meets its destiny in the Bay of Bengal. The Tungabhadra, which is a tributary to the Krishna, is another prominent river that contributes to the water supply and irrigation of the state. These rivers supply not just human uses but also diverse aquatic ecosystems and sustain diverse fish communities, birds, and other wildlife.

2. What is the River Flow Around Karnataka?

Influencing Factors

Precipitation and Runoff

The southwest monsoon is the primary force behind river flow in Karnataka. Variable and intense rain during this season can lead to a high spate of river levels and velocities. However, the volume of rainfall varies from year to year by a huge margin, leading to variations in river flows. At times of poor monsoon, river flows decline, and water scarcity results, especially for agriculture, which is the dominant sector of the state economy. Urbanization and deforestation in the river catchments have altered natural runoff patterns. The increase of urban and town impervious surfaces reduces rainwater infiltration, causing faster surface runoff and greater potential for flooding during heavy rain.

Topography and River Morphology

The steep western slope of the Western Ghats and the relatively flatter interior region govern the direction of flow of the rivers in Karnataka. In the Western Ghats hills, rivers possess a great velocity, eroding valleys and accelerating and accumulating volumes of water while flowing downhill. Once they reach the plains, the flow velocity decreases, and the rivers can widen, with wider channels formed. Varying widths and depths of the rivers occur in their courses. The sections are deep and narrow in some, such as in Western Ghats' gorges, and shallow and wide in plains. The riverbeds consist of rocks, sand, and silt, and the roughness of the riverbed governs the flow resistance, and thus the overall flow pattern.

Reservoir Operations

There are a number of dams and reservoirs built along the rivers in Karnataka for irrigation, power generation, and water storage purposes. Among the most important buildings is the Krishna Raja Sagara (KRS) Dam on the Cauvery River. It is utilized for water storage for irrigation in Mandya and Mysore districts and for hydroelectric power generation. These reservoirs regulate the downstream river discharge by storing water during monsoon and releasing it gradually during the dry season. Reservoir release management is a delicate matter, nonetheless, with numerous times negotiations having to be conducted with the neighboring states due to the interdependent nature of river basins.

Historical Hydrological Events

Floods and droughts have happened in Karnataka. Heavy monsoon rains caused severe floods in some regions of the state in 2019. The inundation of rivers like the Cauvery and its catchments caused low - lying areas to be inundated, displacing many people and impacting crops and infrastructure. Droughts, however, are a long - standing problem, especially in the northern and interior regions of the state. Protracted periods of low precipitation can lead to water shortages for drinking, irrigation, and industrial uses, affecting the livelihoods of millions of people. Observation of these events is extremely crucial for preparing effective flood-control and drought-mitigation policies, as well as for sustainable water-resource management.

3. What is Monitored in River Flow in Karnataka?

Traditional Methods

Surface Drift Float Buoy Method

Surface drift float buoy method is a simple method to determine river flow. A float such as a piece of cork or an empty plastic bottle is thrown into the surface of the river, and its trajectory is measured over a distance and time frame. The velocity of the float is assumed as the surface velocity of the river. Although this method is easy to employ and has minimal equipment needs, it also has limitations. It can measure only surface current and is highly sensitive to wind and surface disturbance. Debris in Karnataka's rivers may also influence the buoy movement and produce erroneous readings.

Anchored Boat Method (Staff Gauge/Current Meter)

In anchored boat technique, a boat is anchored at a single location in the river. A current meter is lowered down to different levels in the water to measure the speed, and a staff gauge is employed to calculate the water level. This method provides a detailed scale velocity profile at a point but is labor-intensive, time - consuming, and dangerous to safety, especially in contaminated or high - velocity rivers. The need for skilled personnel and the danger of hazards in the working environment within the river are the significant drawbacks.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

The Acoustic Doppler Current Profiler (ADCP) gives new and more effective solutions to river flow measurements in Karnataka. In contrast to traditional approaches, ADCP profiler can have non-invasive continuous velocity profiles from the surface to the river bed. It can quickly cover extensive stretches of the river, which is crucial to chart the complex flow patterns in the Cauvery, Krishna, and other such rivers, mainly because of climate change, sedimentation, and human impacts. ADCPs are safer too, as they do not entail direct exposure of the river water.

4. How Does an ADCP Work Based on the Doppler Principle?

An ADCP is operationally founded upon the Doppler principle. It emits acoustic pulses of a known frequency. When these are met by moving particles in the water, such as sediment, plankton, or animals, the returned signal frequency will change in accordance with relative particle motion. If the particles are coming towards the ADCP flow meter, the returned signal frequency increases; if moving away from it, decreases. By analyzing these changes in frequency, the ADCP can ascertain the water velocity at different depths. With multiple transducers of different orientations, it can be employed to measure the three velocity components quantitatively, enabling accurate measurement of the total water flow pattern.

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

Equipment Requirements

Material Reliability

Since ADCP equipment has to endure the tropical climate and potential for water contamination in Karnataka rivers, ADCP equipment needs to be made of very dependable material. These can include corrosion-proof metals like stainless steel or specialized alloys and abrasion-resistant plastics to withstand the harsh river condition, which may involve coming in contact with chemicals from industrial effluent, agricultural runoff, and domestic sewage.

Small Size and Lightweight

The diverse riverine topographies in Karnataka, varying from narrow mountain streams to wide plains rivers, also render small and lightweight ADCPs more suitable. These are easily transported and mounted on different boats or in shallow water reaches, thereby facilitating full flow measurement at different sections of rivers.

Cost - Effectiveness

For long - term and large - scale observation of Karnataka rivers, cost - effective ADCPs are of prime importance. Hardware offering good capability at economical cost facilitates mass deployment, allowing full data acquisition, which is crucial for effective water resource management, flood control, and environmental protection.

6. How to Choose the Right Current Measurement Device?

Methods of Deployment

Boat - Mounted (Moving Boat) ADCP

A boat-mounted ADCP is most appropriate for performing comprehensive surveys of the rivers. It can make quick discharge measurements and map the flow properties across the river width, which will be useful for flood-monitoring, pollution-assessment, and overall river-flow research. In Karnataka, it can be used to survey the Krishna and Cauvery rivers, providing vital information for water management.

Bottom - Mounted (Fixed) ADCP

For getting continuous data for long - term river flow observation, a bottom - mounted ADCP can be installed on the river bed. This provides continuous details of the long - term trends of river flow, which is required to identify the ecological status of the rivers, predict floods, and design water use strategies in an ecologically sustainable manner.

Cableway ADCP

Where cableways are present in sections of rivers, a cableway ADCP can be utilized. It is used where boat deployment is complex or where fixed-bottom installation is not feasible, thus allowing for accurate measurement of flow in challenging river conditions.

Working Frequency

For the rivers in Karnataka, a 600 kHz ADCP would typically be an acceptable choice as it is a compromise between range (horizontally as high as 70 meters) and resolution and can be used to measure the flow in relatively shallow and wide sections of the major rivers. A 300 kHz ADCP, with increased range of as much as 110 meters, can be employed for wider or deeper river sections but with reduced resolution.

Brand Options

Premium ADCP brands such as Teledyne RDI, Nortek, and SonTek are well known globally due to their superior quality and reliable products. Of the Chinese brands, the ADCP supplier’s"China Sonar Panda ADCP" is an affordable option. Made of all-titanium alloy, it is extremely long-lasting and resistant to corrosion, a perfect option for the unfriendly Karnataka river environment. It is also highly cost-effective, and hence it is accessible to a large number of monitoring projects throughout the state. To find out more, visit their website at https://china-sonar.com/.

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