ADCP in the Dniester River Flood Management

1. Where is the Dniester River?

The Dniester River is one of the largest rivers in Eastern Europe, beginning in the Carpathian Mountains, traversing Ukraine and Moldova, and emptying into the Black Sea.

Geographically, in its head area, it passes through mountainous and forested regions. Further downstream, it crosses through open plains and reaches where intensive farming is practiced. On its way, it covers several cities like Chernivtsi in Ukraine and Tiraspol in Moldova. The river is one of the most strategic water sources for irrigation and domestic water supply and transport, as well as a source of electric power for the districts through which it runs.

The catchment areas of the Dniester River develop within a temperatecontinental climate. Rainfall is distributed throughout the year and is somewhat heavier in spring and summer due to frontal systems and thunderstorms. Spring also contributes to the water volume of the river, owing to snow-melting in the Carpathian Mountains. Fluctuations are common, and flooding can happen in case of heavy rainfall or rapid snow-melt.

2. What are the causes of flooding in the Dniester River?

Heavy Rainfall: Heavy and continuous rainfall over the catchment area of the river contributes to the causation of floods. Thunderstorms and frontal systems can provide a lot of water in the shortest period. The infiltration capacity of the soils in that particular region may be surpassed, thus increasing the surface runoff and the rise in the water level of the river.

Snowmelt: Spring snowmelt in the Carpathian Mountains can bring a sudden volume of water into the headwaters of the Dniester River. If the snow melts too rapidly because of a sudden rise in temperature, for instance, then the river cannot cope with great volumes of water, thus creating flood situations downstream.

Topography: Floodplains and low-lying areas along the river provide space for water to spread out and collect. The middle and lower reaches comprise relatively flat plains where the flow of water is slow and thus very liable to flooding. Besides that, the tributaries can add more water during the high-flow period and worsen the flood condition.

Human Activities: Deforestation in the upper catchment area reduces the capacity of the forest to intercept and retain rainwater. A variety of agricultural activities, such as incorrect land drainage and over-irrigation, result in soil erosion and increased surface runoff. Urban development and construction reduce natural water flow and decrease the flood-carrying capacity of the river.

The ADCP current profiler is an instrument of great value while understanding and managing the flow of the river during flood events.

3. How do the ADCPs using the Doppler Principle work?

The working principle of Acoustic Doppler Current Profiler (ADCP) is based on the principle of Doppler. The instrument sends an acoustic signal into the water. Due to flow, the signal finds moving water particles and bounces back to the ADCP. The frequency of the reflected signal is altered due to the Doppler effect.

The ADCP measures the frequency difference of the signal that is sent out and received. Using the frequency shift, it calculates the velocity of the water at each depth. The device normally has many transducers that send and receive acoustic signals in different directions, giving a profile of the water velocity across a section of the river.

For example, the reflected signal would have a higher frequency than it does upon emission if the water is flowing towards the ADCP current profiler, and vice versa if the water flows away. Precise measurement of these changes in frequency and appropriate applications of relevant algorithms yield the actual velocity of the water at various points within the measurement range of the ADCP flow meter.

4. The application of ADCP in the Dniester River floods

Velocity measurement

This will be important in the measurement of the velocity of the water flow during flood events in the Dniester River with high accuracy. It measures continuously in the water flow velocity at different depths and locations, hence providing real - time data about the actual movement of the water. This is crucial information for flood dynamics in predicting the direction and intensity that floodwaters will move.

Application of Flow Measurement

ADCP current profiler is also capable of measuring flow in the Dniester River. It does this by combining the measured water velocities at discrete points across a river section with the known cross-sectional area of that section to calculate the total volume of water flowing through the section per unit time. The information obtained from ADCP flow meter has prime importance in assessing the general volume of water in a flood and in making decisions about flood control and water resource management.

Application in Sediment Transport Research

Other than flow and velocity measurements, ADCP doppler finds application in sediment transport research along the Dniester River during floods. Water carries sediments when it flows. In general, the ADCP current profiler shall detect changes in the backscattered acoustic signal with the presence of sediments. From these changes, an estimation of the amount and its movements may give crucial issues for long-term evolution of the riverbed and the influence of floods on the river sedimentary environment.

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

Flood warning

Monitoring of Velocity and Flow Data: The real-time velocity and flow data from ADCP meter are monitored continuously. If the water velocity is in excess of a certain threshold that is measured, or if the flow rate indicates a big rise, this can signal the peak flood is approaching or that there may be a possible flooding situation. This allows necessary precautionary measures to be taken well in advance by the relevant authorities, such as evacuating people in low-lying areas or reinforcing flood defenses.

Water Level Prediction and Warning: Measured flow data correlated with historical data of water level and appropriate hydrological models can be used to predict future water levels from ADCP data. If the predicted water level is 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 Making: The accurate flow and velocity data from the ADCP profiler can help make decisions on the operational issues concerning water conservancy projects, such as the operation of dams and sluices. For example, depending on the measurement of water flow, regulation in the ways that water is released from a dam can be done to control the water level in the Dniester River, thus lessening or even mitigating the impact from floods.

Flood disaster assessment and emergency response: the ADCP data collected after any flood event could be analyzed for intensity, extent of inundation, velocity of flood flow, amount of sedimentation, and so on. This is highly desirable when emergency response plans are being formulated and actually executed for post-flood reconstruction and rehabilitation work.

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

First of all, what is needed for high-quality measurement of the Dniester River currents includes several aspects. First of all, reliable materials of the equipment in use are needed. The casing of the ADCP flow meter is very important. The casing should be made of titanium alloy. There are some reasons for that: titanium alloy has a number of advantages. High strength which shall enable the equipment to put into consideration the pressure and impact of the running water in the river. Besides material reliability, it is highly corrosion-resistant, something necessary considering the water environment of Dniester River, possibly having different corrosive substances.

Besides material reliability, size, and weight of the equipment must be as small as possible and light in weight. Such a device will be much more convenient to install and operate in variable positions on a river and particularly for areas inaccessible. Low power consumption also is an important factor that enables it to work continuously without changing batteries or connecting to a power source quite often. Furthermore, the cost of equipment should be relatively low to enable large-scale measurement. The lower the cost, the more ADCPs are able to be deployed along Dniester River, providing more ranges of detailed data for flood management.

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

There are many aspects that one had to consider while going to select the appropriate equipment for current measurement in the Dniester River. If the type of measurement required is for horizontal cross-section measurement, then a Horizontal ADCP or HADCP should be selected. In case it is for vertical cross-section measurement, a Vertical ADCP doppler will be applicable.

The second factor is that different frequencies are suited for different water depths. A 600 kHz ADCP, for instance, will be good to go in water depths within 70 m. If the water depth in the Dniester River happens to be within that range and if the measurement requirements match, it will be appropriate to consider a 600 kHz ADCP. Whereas for above 70 m going up to 110 m, it will be more appropriate to use 300 kHz ADCP since providing a more accurate measurement in that depth.

There are some well-known ADCP current meter brands available in the market such as Teledyne RDI, Nortek, and Sontek. However, for those who look for something budget-friendly perhaps China Sonar PandaADCP fits the bill. 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.