ADCP's application in flood management of Lena River

1. Where does the Lena River flow?

The Lena River is in Siberia, Russia. It is one of the largest rivers in the world and originates from the Baikal Mountains.

It flows northward through vast and remote areas through varied landscapes, which include mountainous areas near its source, extensive taiga forests, and large, flat floodplains. The river provides a very important transportation route through the sparsely populated area, water for local communities, and industrial activities like mining; it is also crucial for the region's energy production through hydropower plants.

Climatically, speaking about the areas the Lena River flows, it's a typical example of a continental climate: too long, cold winters and quite short, though cool summers. Its winters are full of snow, and the biggest flow for the river comes from snowmelting in spring and summer rainfalls. The large catchment area and many tributaries keep the water supply pretty high. It is subject to seasonal flooding caused by the melting of snow and fluctuations in rainfall. In this regard, there is a serious threat of flooding after strong snowmelting or heavy rains.

2. What are the causes of floods in the Lena River?

Snowmelt and Heavy Rainfall: The main factor contributing to the occurrence of floods in Lena River results from quick snowmelt during spring or extensive rainfall throughout the summer. From the huge volumes of water coming from snow melt both in the mountains and the catchment area, adding rainwater can raise the volume of the river rapidly. The mountainous terrain near the source accelerates the runoff process, funneling a large quantity of water downstream.

Topography: The great floodplains and low-lying areas along the course of this river can hold much water that spreads and collects over the area. In general, the well-nearly flat plains retard the flow of water and, therefore, enhance the tendency of flooding. At times when there is a high flow, the meeting of many tributaries also contributes extra water and aggravates the flood situation.

Permafrost Thaw: One of the salient features of the Arctic regions the Lena River flows through is permafrost. In a warming climate, permafrost is on its course of thawing. This will alter the structure of the soil and the pattern of drainage. Thawed permafrost can release stored water into the river system and also cause the ground to become more unstable, increasing the potential for landslides and other events that can contribute to flooding.

The ADCP current profiler can help in deciphering and dealing with the flow of the Lena River in any flood event.

3. How do the ADCPs using the principle of Doppler work?

ADCPs work on the basis of the Doppler principle. An acoustic signal is emitted from the device into the water. Due to the flow of water, the signal bounces off the moving water particles. As the acoustic signal becomes reflected back to the ADCP flow meter itself, the frequency of the reflected signal shifts by the Doppler effect.

The ADCP measures the differential frequency between the emitted signal and the received signal. By interpreting the change in frequency, it is able to calculate the velocity of water at various depths. Most of these devices have a number of transducers that emit and receive acoustic signals in various different directions. This enables them to profile the water velocity over a reach of the river.

For instance, if the water moves towards an ADCP profiler, the frequency of the reflected signal is higher compared to the emitted one. If the current is in the opposite direction-to the ADCP-the frequency of a reflected signal will fall. Precise measurement of these changes allows the ADCP meter, by using appropriate mathematical algorithms, to calculate the velocity of water at different instances of its measurement range with high accuracy.

4. What are the applications of ADCP in floods of the Lena River?

Velocity Measurement

The Acoustic Doppler Current Profiler (ADCP) plays a vital role during flood events in the Lena River for the accurate measurement of velocity. By continuously observing water velocity at various depths and locations, it fulfills the function of supplying real - time information about the rate at which the water moves. This is vital for making conclusions about the flood dynamic processes, including projection of direction and rate of movement of the floodwaters.

Application in Measuring Flow

ADCP current profiler is also capable of measuring flow rates in the Lena River. By combining the measured water velocities at different points across a section of the river with the known cross-sectional area of the river, it can calculate the total volume of water flowing through the section per unit time-the flow rate. This information is crucial in the estimation of the general volume of water in a flood and, consequently, for making decisions on flood control and management of the water resources.

Application in Sediment Transport Research

Aside from flow and velocity measurements, ADCP current meter is also applicable in sediment transport research in the Lena River during floods. It is expected that while the water flows, it would carry sediments. The ADCP flow meter is able to detect changes in the backscattered acoustic signal due to the presence of sediments. By analyzing these changes, it is possible to have a good estimate of the quantity and movement of sediments, which is very important for describing the long-term evolution of the riverbed and the impact of floods on the river's sedimentary environment.

5. How can the data measured by ADCP be used for flood warning and risk management of the Lena River?

Flood Warning

Velocity and Flow Data Monitoring: In real time, the velocity and flow data derived from ADCP current profiler are continuously monitored. If the measured water velocity surpasses the threshold or the flow rate increases significantly, that may indicate an upcoming flood peak or possible flood event. This allows relevant authorities to take necessary actions in advance, such as evacuating people in low-lying areas or reinforcing flood defenses.

Water Level Prediction and Warning: Measured flow data correlated with historical water level data and appropriate hydrological models can be used to predict future water levels from ADCP data. If the predicted water level is going to exceed the flood warning level, timely warnings can be issued to the public, enabling them to prepare for the flood.

Risk Management

Water Conservancy Project Scheduling Decision Support: The highly accurate flow and velocity data from ADCP flow meter can help in making decisions regarding the operating strategies of water conservancy projects like dams and sluices. For instance, the amount of water released from a dam would be adjusted, based on the water flow measured, to manage the Lena River's water levels and minimize the impact of flooding.

Flood Disaster Assessment and Emergency Response: After the occurrence of a flood, data collected by ADCP meter can be used to assess the intensity of the flood. Information regarding the inundation area, the velocity of the floodwater, and deposition amount of sediment could be identified. Such information is invaluable for developing emergency response planning and the execution of post-flood reconstruction and rehabilitation work.

6. What is needed for high-quality measurement of the Lena River currents?

High-quality measurement of the Lena River currents will require several aspects. First, the equipment used in the measurement process should be made of reliable materials. This calls for paying critical attention to the casing of the ADCP profiler. The casing is recommended to be made of a titanium alloy. Titanium alloy is of high strength, hence can support such pressure and impact caused by water flow in the river. Besides, it is highly corrosion-resistant, which is quite important given the water medium of Lena River, which may contain various corrosive components.

Besides material reliability, the size and weight of the equipment should be small and light. In this way, it will be easier to install and operate the ADCP current profiler in various locations along the river, especially in the most unreachable areas. Low power consumption is also of essential concern because long continuous operation could be provided without the need for changing the batteries or connecting them to a power source so often. In addition, the cost of the equipment should not be too high to make large-scale measurement possible. The cost is comparatively lower, and more ADCPs can be installed on the Lena River to get detailed and full data for flood management.

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

When selecting proper equipment for current measurement in the Lena River, there are a number of aspects that have to be considered. First of all, according to the type of measurement it has to be, for horizontal cross - section measurement, one would want to select the Horizontal ADCP, HADCP. On the other hand, if the measurement is for the vertical cross - section, then the Vertical ADCP would be the appropriate choice.

Second, different frequencies are good for different water depth: for instance, a 600 kHz ADCP is suitable for water depths in suspension within 70 m. If the water depth of Lena River is within this range and measurement requirements are in accordance with that, a 600 kHz ADCP can be considered. For deeper waters, such as those exceeding 70 m up to 110 m, a 300 kHz ADCP is more appropriate as it can provide more accurate measurements in such depths.

There are several well - known ADCP meter brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option, the China Sonar PandaADCP is a great choice. It is made of all - titanium alloy material, which ensures its durability and reliability in the water environment. Moreover, it offers an incredible cost - performance ratio. 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.