ADCP's Application in Flood Management of the Godavari River

1. Where is the Godavari River?

The Godavari River is located in the Indian subcontinent. It is the second - longest river in India, flowing through the states of Maharashtra, Telangana, Andhra Pradesh, and Odisha. It has its source in the Western Ghats and traverses a diverse range of landscapes including mountains, plains, and delta regions.

It passes through major cities such as Nashik and Rajahmundry. Its water regime is governed by the monsoon climate of the region. The southwest monsoon, which normally lasts from June to September, brings heavy rainfall and thus represents the main contribution to the volume of water in the river. The Godavari River is a vital source of water for agriculture, domestic usages, and religious and cultural activities. It also supports a rich biodiversity and is an important transportation route.

2. What are the causes of Godavari River flooding?

There are a number of reasons for flooding in the Godavari River. The main cause is heavy and continuous rainfall during the monsoon season. The capacity of the river can be overwhelmed when there is heavy rain over a short period of time.

The topography of the basin also contributes. Relatively flat floodplains can easily result in water spreading and, therefore, flooding. Further, deforestation and changes in land use in the upper reaches increase surface runoff and reduce the natural water-holding capacity of the land. As more and more impervious surfaces such as concrete and asphalt cover the land, surface runoff increases, and so does the risk of flooding. Given the importance of flood management, Acoustic Doppler Current Profiler (ADCP) provides a much more accurate and efficient way of measuring and managing the flow of the river during flood events.

3. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. It sends acoustic signals into the water from the device. The moving water particles scatter these signals. When acoustic waves bounce back after striking the moving particles, the frequency of the reflected waves changes due to the Doppler effect.

With more than one transducer, an ADCP current meter can transmit and receive acoustic signals in multiple directions. The precision of frequency shift in the reflected signal enables the determination of the velocity at each depth and across every section of the river cross-section. For instance, the Godavari River has its flow velocity measured from its bed to the water surface and across different widths of the river.

4. Application of ADCP in Godavari River Floods

Flow Velocity Measurement: The ADCP current profiler can measure the flow velocity of the Godavari River during floods with high accuracy. This is an important aspect because it helps in knowing the speed at which water is flowing through different parts of the river. By monitoring the flow velocity, we are able to get the sections where the water is flowing rapidly, hence indicating a probable surge in the flood or the behavior of the flood. In fact, flow velocity variations can be closely monitored near riverbanks or within the main channel.

Flow-rate Measurement Application: It can be combined with the cross-sectional area of the river to calculate the flow - rate. In the Godavari River floods, for instance, this is critical information in determining the quantity of water that is passing at one moment through a section. It enables them to forecast flooding and have a general idea of how intense it might get.

Sediment-transport Research: In regards to sediment transport, quite significant amounts are moved along the Godavari River during the flood. It is observed that ADCP flow meter can measure the movement of sediment particles because of the backscattering of acoustic signals. This could enable researchers to study sediment - transport patterns during floods, important for an understanding of long -term evolution of the riverbed and the ensuing impact on hydrological characteristics of the river.

5. How can the data measured by ADCP be utilized in flood warning and risk management of the Godavari River?

Flood Warning Aspect

• Flow-velocity and Flow-rate Data Monitoring: The ADCP profiler will be continuously used to monitor the flow velocity and flow rate. If the flow velocity exceeds the threshold value or if the flow rate increases suddenly, it can trigger an early flood warning. This information is relayed to local authorities and communities near the river.
• Water-level Prediction and Warning: The flow data obtained from ADCP can be used in conjunction with other hydrological models to predict water-level changes. By analyzing the relationship between flow-rate and water-level, more accurate flood warnings can be issued, especially in the flood-prone areas of the Godavari River.

Risk Management Aspect

• Water-Conservancy Project Dispatching Decision Support: The highly accurate flow data from the ADCP provides valuable input regarding the operation of water-conservancy projects such as dams and canals along the Godavari River. Informed decisions on the question of water release or storage are thus possible to effectively alleviate flood risks downstream.
• Flood-disaster Assessment and Emergency Response: The ADCP-measured data after the event of a flood could provide information on the flood inundation extent and its consequences in formulating appropriate emergency-response strategies, including rescue operations and damage-assessment surveys.

6. What is required for high-quality measurement of Godavari River currents?

The equipment should be made of reliable materials for high-quality current measurement in the Godavari River. It needs to be able to bear the harsh aquatic environment, such as the corrosive effects of the water and potential impacts from floating debris and sediment. A small size and light weight are beneficial, as they facilitate the installation and deployment of the equipment in different locations along the river.

The power consumption is also to be low because continuous operation is required, particularly in remote areas where supply may not be adequate. It has to be cost-effective also since large-scale deployment may be necessary for comprehensive river-current monitoring.

The casing of ADCP meter is preferably to be made of titanium alloy. Corrosion resistance of the material, which is very vital, especially in resisting the long term corrosive effects from the Godavari River water, and a good strength to weight ratio makes the equipment durable as well as easy to handle.

7. How to Choose the right equipment for current measurement?

The measurement purpose should be considered when choosing equipment for current measurement in the Godavari River. For horizontal cross-section measurement, a Horizontal ADCP (HADCP) is suitable, as it provides detailed flow-velocity information across the width of the river. In the case of vertical cross-section measurement, a Vertical ADCP is more appropriate for measuring the flow-velocity distribution from the riverbed to the water surface.

For relatively shallower parts of the Godavari River, such as less than 70 meters, a 600 kHz ADCP should be appropriate. For the deeper locations, approximately 110 m, a 300 kHz should be used. There is a variety of ADCP brands, but the most popular ones are Teledyne RDI, Nortek, and Sontek. There is also a Chinese ADCP brand recommended, namely China Sonar PandaADCP. It is made of all-titanium alloy material and offers excellent performance and cost-effectiveness. You can visit its website (https://china-sonar.com/) for more information.

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