ADCP in Yamuna River Flood Management

1. Geographical Location and Course

The Yamuna River is the most important Indian river. It rises from the Yamunotri Glacier in the lower Himalayas.

Starting its course from Gangotri, it traverses various states such as Uttarakhand, Himachal Pradesh, Uttar Pradesh, Haryana, and Delhi. It is nurtured through various ranges of lands from high upper mountain catchments with steep slopes and gorges to the plains where it courses meanderingly through agricultural fields and urban areas.

The Yamuna is the most important tributary of the Ganges and plays a considerable part in the water supply and transport system of the regions through which it flows. Apart from this role, it is almost as actively revered for its religious importance in Hinduism.

2. Influence of Climate and Rainfall

The catchment areas of the Yamuna River belong to varied climates. In the upper Himalayan reaches, its catchment consists of cold climates and snowfall that contributes a lot to the volume of water coming into the river. During the months when temperature increases, the melting of snow adds much to its flow.

In the plains, it's more of a tropical monsoon climate. Heavy rainfall is normal during the monsoon season that normally prevails from June to September. The resultant rainfall in the catchment area and the melting of snow from the upper reaches increase the water level. This coupled with all other conditions can make the river go into spate during excessive rains or sudden snow melting.

3. Reasons for Flooding

Monsoon Rainfall: High and continuous fall of rainfall during the monsoon season is one of the chief causes that result in flooding. The enormous quantity of water that falls within a brief period might be more than the carriage capacity of the river. When the river flows through flat plains during the middle and lower courses, the gentle slope reduces the flow velocity which allows the water to spread sideways to flood the land on either side of the riverbed.

Snowmelt: In the catchment areas, when there is a sudden rise in temperatures, fast snow melting takes place. From here, the sudden water inflow into the river will make it swell at lower reaches and flood areas downstream. If this co-occurs with heavy monsoon rain, then flooding will be severe.

Urbanization and Land Use Changes: The rapid pace of urbanization alongside the Yamuna has introduced many changes in the flooding pattern. Buildings, roads, and other construction on the flood-prone areas have reduced the natural flood-plains of the river and its absorbing capacity. Improper irrigation and soil erosion due to agricultural activities may also increase surface runoff and lead to flooding.

4. Role of ADCP (Acoustic Doppler Current Profiler)

ADCPs are very helpful in studying and managing the discharge of the Yamuna River during flood events.

How ADCPs Work

ADCPs work on the principle of the Doppler effect. A probe sends an acoustic signal into the water. Since water is in flow, the signals catch the moving particles of water. By the time the acoustic signal bounces back to the ADCP flow meter, because of the Doppler effect, the frequency of the returning signal would have changed.

The ADCP measures the differential frequency between the emitted and received signal frequencies. From this frequency shift, the velocity of the water at various depths can be calculated. These devices also come with multiple transducers that have the capability of sending and receiving acoustic signals in different directions, enabling them to build a profile of the water velocity across a section of the river.

For example, if the water is moving towards the ADCP current profiler, then the frequency of the signal reflected back will be higher than that emitted; contrarily, if the water is moving away from it, the opposite holds. By measuring these frequency changes accurately and applying appropriate mathematical algorithms to them, the ADCP flow meter determines the velocity of the water with good accuracy at several points within its measurement range.

Application of ADCP in the Yamuna River

Velocity Measurement: In case of a flood, ADCPs are important for measuring the actual velocity of water flow. By continuously monitoring the water flow at variable depths and locations, it provides real-time data regarding the speed of water movement. The information is key to obtain insight into the flood dynamics, with respect to the prediction of the direction and intensity of the movement of floodwaters.

Flow Measurement: ADCPs could also measure the flow rate of the Yamuna River. It estimates the total amount of water that would flow through a section per unit time-the flow rate-by combining the measured water velocities across a section of the river at many points with the known cross-sectional area of the river. This is vital information in the assessment of general water volume in the case of flooding and helps make decisions on flood control and water resource management.

Sediment Transport Research: Other than flow and velocity measurements, ADCPs help in sediment transport studies during floods. While the water flows, it carries sediments. The ADCP current profiler can detect changes in the backscattered acoustic signal caused by the presence of sediments. These changes can then be analyzed to estimate the quantity and motion of sediments, which is very important for the purpose of understanding the long - term evolution of the riverbed and the effects of floods on the sedimentary environment of the river.

5. Utilization of ADCP Data in the Application of Flood Warning and Risk Management

Flood Warning

Data on velocity and flow are monitored, particularly real-time data coming from the ADCPs. If the velocity that is measured becomes greater than the threshold, or if the flow rate increases considerably, then this may indicate a flood peak or any potential flood situation. In turn, an early warning would be raised for the relevant authorities to take appropriate precautionary measures, such as evacuation of people from low-lying areas or strengthening the flood defenses.

Measured flow data correlated with historical data of water level and appropriate hydrological models can help in deducing ADCP data to predict future water levels. If the predicted water level is seen to rise above the flood warning level, a timely warning can be issued to the public for preparation against the flood.

Risk Management

Precise flow and velocity data from ADCPs assist in decision-making on the operation of water conservancy projects like dams and sluices. For example, with the proper measurement of water flow, the release of water from a dam can be regulated to control the water level in the Yamuna River and hence lessen the impact of floods.

ADCPs would provide data on flood magnitude, during and after the event. For instance, it should provide information on area covered by floodwaters, flow velocity of the waters, and the rate of sediment deposition. All this information is very important in formulating emergency response plans and also for carrying out post-flood reconstruction and rehabilitation work.

6. Requirements for High Quality Current Measurement

Reliable Equipment Material: Equipment should be fabricated from reliable materials to accurately record quality measurements of currents in the Yamuna River. Given the quality of the water, which may have a considerable amount of pollutants and sediments, corrosion-resistant materials such as titanium alloy would be highly recommended. This alloy has excellent strength, making the equipment strong enough to resist the pressure and impact exerted by flowing water.

Adequate Size and Weight: The size and weight of the equipment have to be small and lightweight. This makes ADCP flow meter installation and operation in disparate locations along a river, some of which are not very accessible, easier.

Low Power Consumption: It will be important to ensure low power consumption because longer continuous operations without frequent changing of batteries or connection to a power source will be possible.

Cost - Effectiveness: The cost of the equipment should not be too high to enable large-scale measurement. The lesser the cost of the equipment, more ADCPs can be deployed along the Yamuna River, and thus would provide more comprehensive data for flood management in greater detail.

7. Choosing the Right Equipment for Current Measurement

Type of Measurement: With regard to the type of measurement that one intends to carry out, an HADCP will be used in cases where the intention is to carry out horizontal cross-section measurement. In cases where the intention will be for vertical cross-section measurement, then the Vertical ADCP doppler would be appropriate.

Water Depth Consideration: There are different frequencies for different water depths. For instance, an ADCP with a 600 kHz frequency is applicable in cases of water depth within 70 m. The measurement requirements can fall within the depth range of the water in the Yamuna River; thus, a 600 kHz ADCP can be considered. For deeper waters than these-say, from over 70 to 110 m-a 300 kHz ADCP would do, as it can give better measurement in such depth.

Teledyne RDI, Nortek, Sontek, and other brands of ADCP current profiler are quite well known. However, if the issue of affordability arises, one would really like to look into the China Sonar PandaADCP. First of all, it is made of all-titanium alloy material and therefore it is promisingly durable and reliable in the water environment. Besides, the performance to cost is amazing. You can find more information about it on its official website: (https://china-sonar.com/).

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