Why Is River Flow in Rajasthan Measured?

1. Where is Rajasthan?

Geographic Background

Rajasthan, the biggest state of India by area, lies in the northwestern part of the nation, encompassing approximately between 23.3°N - 30.12°N latitude and 69.30°E - 78.17°E longitude. The state lies in the arid and semi-arid geography, with most of it being part of the Thar Desert, also known as the Great Indian Desert. The Aravalli Range, which is among the oldest of the world's mountain ranges, runs through the state from southwest to northeast, providing some relief from the otherwise flat sandy terrain. Rajasthan has a harsh continental climate, with searing summers when temperatures above 50°C prevail between April and June, and cold winters from November to February with temperatures falling to as low as 0°C in some regions. Precipitation is minimal and highly irregular, with the majority of the state receiving less than 500 mm of rainfall annually, and water resources are consequently very valuable.

Humanities and culture

Rajasthan is a place with rich history and rich culture. It was once a collection of maharaja states, and their memories are visible in the massive palaces, forts, and havelis (mansions) that dot the state. Jaipur, the capital, known as the "Pink City" because its buildings are rose-colored, is typical of the blend of Rajput and Mughal architecture. Udaipur, at times also called the "City of Lakes," is famous for its lakes and stunning palaces, whereas Jaisalmer, with the golden sandstone buildings, serves as a reminder of the desert heritage of the state.

Rajasthani culture is a colorful palette of folk heritage. The local festivals and celebrations would not be complete without traditional dances like the Ghoomar, women's dance in long, flowing, multi-hued skirts, and the Kalbeliya, a snake - charming - named dance by the Kalbelia tribepeople. The state also has traditional handicrafts, like intricately block-printed clothes, lovely jewelry, and hand-sculpted wooden furniture, showcasing the skill and imagination of local artisans. The Pushkar Camel Fair, which is among the world's largest livestock fairs, is as much a conference of business as a celebration of Rajasthani culture and attracts tourists from all over the globe.

Hydrology and River Overview

The Chambal River is one of Rajasthan's major river systems flowing through the north-east part of the state. It starts in the Vindhya Range in Madhya Pradesh and moves northwestwards to become a part of the state border between Rajasthan and Madhya Pradesh before merging into the Yamuna River. The other significant river is the Luni River, which is the only major river entirely within Rajasthan. It originates in the Aravalli Range at Ajmer and flows westwards into the Thar Desert, where it often dries up before it reaches the Arabian Sea during the dry season.

They are also vital for the ecosystem and human utilization of Rajasthan. The Chambal River, ecologically, contains a range of aquatic life ranging from the Ganges River dolphin, certain species of fish, to numerous migratory birds. The river and wetlands that run alongside it are responsible for maintaining the ecological balance of the area as well. For human use, they are the primary sources of water for domestic consumption, agricultural uses, and industrial use. However due to the arid climate and lack of water, water from these rivers is highly controversial. Agriculture, characterized by drought-resistant crops like bajra (pearl millet) and jowar (sorghum), is dependent on the river water available for irrigation. The rivers are also utilized in some areas for the generation of hydroelectric power, though the scale of such projects is relatively small.

2. How is the River Flow Near Rajasthan?

Influencing Factors

Precipitation and Runoff

The most significant factor influencing river flow in Rajasthan is precipitation. Rainfall is extremely low in the state, and it is highly irregular in volume as well as space. June to September monsoon rains are the sole source of water for the rivers. River stages rise in good monsoon years, and there is sufficient water available for various uses. In drought years, which are very common, river flows decline significantly, drying up sometimes even wholly. Urbanization and deforestation in catchment basins have also altered the natural runoff patterns. The increase in impervious surfaces in urban and metropolitan areas lowers rainwater infiltration, leading to higher but often truncated surface runoff.

Topography and River Morphology

Rajasthan's semi - arid and arid topography with large deserts and the Aravalli Range affects the river flow. The Luni River, which runs through the desert, has to battle with high infiltration and rate of evaporation in the sandy soil, leading to its flow reducing rapidly as it moves downstream. The Chambal River, on the other hand, flows over a relatively more stable terrain in regions of Rajasthan but is spurred by the rock and broken country of the Vindhya and Aravalli tracts. The depth and width of such rivers vary considerably, as the Chambal is deeper and wider at certain places compared to the Luni, which is generally shallow and seasonal. The river beds are sandy, gravelly, and occasionally rocky outcrops, which influence the resistance to flow and the pattern of flow.

Reservoir Operations

Various dams and reservoirs have been built across the rivers in Rajasthan for power generation, irrigation, and water storage. For example, Bisalpur Dam on Chambal's tributary Banas supplies water to Jaipur and other regions for domestic and agricultural use. The reservoirs regulate river flow downstream by retaining water during the monsoon season and discharging slowly during the dry season. But their operation is regulated strictly to fulfill the needs of different sectors as the state has long been suffering from water scarcity.

Historical Hydrological Events

Rajasthan has experienced the worst of droughts and occasional floods in its past. Some parts of the state suffered from a drought in 2019 when the Luni River dried out in most reaches. This caused major water shortages for both the people and the animals, affecting the harvests of crops and the lives of thousands of people. The Chambal River, on the other hand, has also been responsible for floods in years with excess monsoons. Heavy rains in the upper catchments of the Chambal in 1986, for instance, caused flooding in the Chambal river and northeast Rajasthan, leading to crop loss, damage to public property, and displacement of local populations. Continuous monitoring of such occurrences will be crucial in developing drought-mitigation and flood-control policies, as well as for providing sustainable water resources management in the state.

3. How is River Flow in Rajasthan Observed?

Traditional Methods

Surface Drift Float Buoy Method

Surface drift float buoy method is the basic method of measuring the flow of a river in Rajasthan. A simple buoy such as a cork or plastic bottle is floated on the surface of the river, and the drift is noted over a measured distance and time interval. The velocity of the buoy is then taken as the surface velocity of the river. This is an easy method to employ but requires minimal equipment. It possesses very great demerits, though. For the dry rivers of Rajasthan, the excessive sand, debris, and prevailing winds can easily disrupt the movement of the buoy, leading to poor measurements. It can only measure surface flow and does not provide information on flow at varying depths.

Anchored Boat Method (Staff Gauge/Current Meter)

In anchored boat technique, the boat is kept stationary in a fixed position in the river. A current meter is allowed to drop at different depths to be measured from the water velocity, and staff gauge is used to measure the water level. Such a system delivers an exact velocity profile at a point but is highly labor - and time - intensive, and also dangerous in nature, especially in the case of shallow or fast - flowing rivers. In Rajasthan, where its rivers have strong currents in some places and shallow water with hidden rocks in others, the absence of skilled personnel and the risks involved in working under those conditions in these rivers are major drawbacks.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

Acoustic Doppler Current Profiler (ADCP) is a more advanced and efficient way of observing river flow in Rajasthan. Compared with the traditional techniques, ADCP is capable of delivering unbroken velocity profiles from the surface of the river to the river bed non - invasively. It is capable of scanning huge parts of the river quickly, which is essential to understanding the complex flow patterns of the Chambal, Luni, and other rivers in view of the effect of the arid climate, sedimentation, and human activities. ADCPs are also safer to use as they do not entail direct human contact with the river water, which may be contaminated or in poor conditions.

4. An ADCP Operation According to the Doppler Principle

An ADCP operates according to the Doppler principle. It transmits an acoustic pulse of a specific frequency. When this signal collides with moving particles in water, e.g., sediment, plankton, or small animals, the backscattered signal frequency depends on the relative motion of the particles. If the particles are moving towards the ADCP current profiler, the frequency of the reflected signal is greater; if moving away, lesser. Based on these frequency differences, the ADCP can calculate the water velocity at different depths. With more than a single transducer at multiple angles, it can even measure the three-dimensional components of the velocity and accordingly calculate the composite water flow pattern.

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

Equipment Requirements

Material Reliability

Because the dry environment of Rajasthan's rivers is extremely demanding, with exposure to sand, dust, and occasional flooding, ADCP current meter equipment needs to be made from incredibly durable materials. Hard plastics and abrasion- and corrosion-resistance metals like stainless steel or specially designed alloys must be used to withstand erosive and often corrosive environments. The equipment needs to be able to withstand extremely hot temperatures, fluctuating from extremely hot during summer and cold during winter.

Small Size and Light Weight

Rajasthan's diversified riverine topography, from meandering desert streams to large rivers with variable accessibility, makes small and light weight ADCPs more manageable. They are easily portable and can be installed on varied crafts, or even in remote locations with limited access, making extensive flow measurement possible in varied sections of the rivers.

Cost - Effectiveness

For large - scale and extensive observation of Rajasthan's limited river resources, cost - effective ADCPs are a must. Equipment offering good performance at reasonable cost facilitates widespread application, allowing full data acquisition, necessary for effective water resource management, prevention of drought, and flood management in the water - starved state.

6. How to Choose the Right Current Measurement Equipment?

Deployment Methods

Boat - Mounted (Moving Boat) ADCP

A boat - mounted ADCP is most suitable for conducting detailed surveys of the rivers. It can quickly measure the discharge and map the flow characteristics over river width, which can be utilized for flood - monitoring, pollution - assessment, and general river - flow studies. In Rajasthan, it can be used for the measurement of the Chambal River and other large water bodies, which can provide useful information for water management and understanding the impact of climate change on river flows.

Bottom - Mounted (Fixed) ADCP

In order to obtain long-term continuous monitoring of river flow, a bottom-mounted ADCP meter can be installed on the riverbed. This provides continuous records of long-term trends in river flow, which are required to know the ecological health of the rivers, predict drought or flood, and plan sustainable plans for water use, especially in a state where water is a limited resource.

Cableway ADCP

Where cableways cover sections of the rivers, a cableway ADCP can be used. This method is used where deployment by a boat is inconvenient, or fixed-bottom deployment is not practical, to make accurate flow measurements in rough river conditions, such as in narrow gorges or areas where there are strong currents.

Working Frequency

For Rajasthan rivers, a 600 kHz ADCP will normally be appropriate since it provides a satisfactorily balanced range (up to 70 meters in the horizontal plane) and resolution, which is adequate for recording the flow in relatively wide and shallow sections of the main rivers. A 300 kHz ADCP with an extended range of up to 110 meters can be used for wider or deeper river courses but at reduced resolution.

Brand Recommendations

Reputable and high-quality ADCP brands such as Teledyne RDI, Nortek, and SonTek are renowned globally. Chinese brands also include the ADCP supplier’s "China Sonar Panda ADCP," which is cost-effective. It is made of all-titanium alloy, which gives it high durability as well as corrosion resistance, and is capable of weathering the tough environment of Rajasthan's rivers. It is also very cheap and therefore accessible to use in the majority of the monitoring projects in the state. For further information, you can visit their website at https://china-sonar.com/.

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