ADCP in the Management of Jinsha River Floods

1. Location of Jinsha River

The Jinsha River is one important part of the Yangtze River system in China. The river lies in the southwestern part of the country. Its source is from the Qinghai-Tibet Plateau.

Geographically, it passes through a set of complex and diversified landscapes: while in the upper parts, it runs through areas of high elevation with towering mountains and deep valleys, further downstream, it has to course its way through undulating regions comprising mixed mountainous terrains and plateaus. In the process, it supports an essential local water supply both for human enterprises and ecological regimes.

For climate and rainfall, the variation in altitude presents a wide range of climates for the area over which the Jinsha River flows. The climate is relatively cold, with much snowfall during winter, and presents itself on the plateau during the upper reaches. During the warm seasons, the melting of snow adds to the water body. In the lower and middle reaches, it is partly influenced by monsoon climate with a marked wet season from May to October. Because of greater rainfall in this period, coupled with snowmelt from the upper reaches, there are fluctuations in water levels, and when there is excessive input of water, there may be flooding.

2. What are the causes of flooding of the Jinsha River?

Heavy Rainfall and Snowmelt: Heavy rainfall in the catchments during the wet season, coupled with rapid snow melting in the upper reaches, contributes to floods. This is because enormous quantities of water are brought within a short period into the river, hence raising its water level. Mountainous topography in the upstream catchments accelerates runoff processes and sweeps a high volume of water downstream with great speed.

Topography and River Characteristics: The valleys and comparative narrow parts along its course make the water collect in some places and flow with more force. Besides, the Jinsha River has many tributaries, and when those also have high water during heavy rains or snow melting, they carry more water, adding to the flood situation.

Man-Made Effects: The practices that involve deforestation of the catchment area reduce the area's ability to intercept and retain rainwater. This will also increase soil erosion. Eroded soil sediments are deposited in the river, reducing its carrying capacity. Moreover, infrastructure such as building roads and certain water conservancy projects inappropriately will damage natural water flow and drainage.

The ADCP current profiler is a more advanced and convenient measurement method for understanding and managing the flow of the river during flood events.

3. How does an ADCP using the Doppler Principle Work?

Principle of Doppler is the basis on which ADCPs work. The device transmits a sonic signal into the water. When in flow, the water acts with its moving particles. Due to the Doppler effect, the frequency of the reflected signal changes when the acoustic signal is reflected back to the ADCP flow meter.

The ADCP measures the frequency difference between the emitted signal and the returned signal. With this frequency shift, it calculates the speed of the water at each depth. The ADCPs normally have several transducers that are capable of sending out and receiving acoustic signals in various directions. In that way, they can create a profile of water velocity across a section of a river.

For example, if the water is coming towards the ADCP profiler, it will return a signal at a higher frequency from the one that was emitted. If the water is flowing away from the ADCP flow meter, the returning signal will be at a lower frequency. Accurate measurement of these frequency shifts with proper algorithms allows determination with a high degree of accuracy exactly how fast the water is in different portions of its measurement range.

4. About which aspects are ADCP used in floods of the Jinsha River?

Velocity measurement

ADAcoustic Doppler Current Profiler (ADCP) plays an important role in measuring the velocity of water flow with high accuracy during flood events within the Jinsha River. It monitors real-time water velocity at different depths and locations within the flow. Information of this nature remains paramount for any serious analysis in understanding dynamics related to floods, such as the direction or intensity of the movement of floodwaters.

Flow Measurement Application

Such measurements can also be extended to the determination of flow rates in the Jinsha River by ADCP current profiler. Combining the measured water velocities at different points across a section of the river with known cross-sectional area of the river, the total volume of water flowing through the section per unit time-the flow rate-can be calculated. This is very important information needed to determine the total volume of water in a flood and necessary for making decisions on control and management of water resources.

Application in Sediment Transport Research

Besides the flow and velocity measurements, the ADCP flow meter can be useful in the study of sediment transport along the Jinsha River during flooding. While water flows, it carries with it sediments. The ADCP can detect the variations in the backscattered acoustic signal produced due to the presence of sediments. From this, the concentration and the movement of sediments can be estimated, which are important to understand the long-term evolution of the riverbed and the impact of floods on the sedimentary environment of the river.

5. How to apply data measured by ADCP in the flood warning and risk management of the Jinsha River?

Flood Warning

Velocity and Flow Data Monitoring: In the real-time mode, ADCP doppler will continuously monitor the real velocity and flow data. In case the measured water velocity exceeds beyond a certain limit or if the flow rate increases drastically, then these are indications that a flood peak is imminent or will arrive shortly. This thus allows for an early warning to be raised to enable the relevant authorities to take necessary precautionary measures, such as evacuation of people from low-lying areas or reinforcing flood defenses.

Water Level Prediction and Warning: Measured flow data correlated with historical water level data can be used to predict future water levels by applying appropriate hydrological models. In case the predicted water level is expected to exceed the flood warning level, necessary warnings can be issued to the public in time for preparation against the flood.

Risk Management

Support of Decision Making for Scheduling of Water Conservancy Project: The accurate flow and velocity data from ADCP flow meter can help make decisions on the operation of water conservancy projects such as operating dams and sluices. Based on the measured water flow, for instance, regulation of water release from a dam can control the water level in the Jinsha River to mitigate the impact of floods.

Flood Disaster Assessment and Emergency Response: Based on the ADCP data, the extent of inundation, velocity of flood water, and the sediment depositions caused by a flood event can be calculated. This information is highly valuable while formulating the emergency response plans as well as for post-flood reconstruction and rehabilitation works.

6. What is needed to measure the current of Jinsha River with superior quality?

The measurement of Jinsha River currents with superior quality requires a variety of factors. First, equipment should be of reliable material. This involves the casing of ADCP meter, which should be made of titanium alloy. Its strength is so high that it can bear the pressure and impact caused by water flow in the river. Besides, its corrosion resistance is very high, which will be necessarily required because there could be all kinds of corrosive elements in the water environment of Jinsha River.

Besides material reliability, the size and weight of equipment should be small and light. Thus, the ADCP flow meter  will be installed and operated easily at various points of the river; in particular, it is meant for hard-to-reach areas. Low power consumption is necessary for the device because the possible operation should be longer without frequently replacing batteries or connecting to a power source. The cost of the equipment also should not be high to enable large-scale measurement. That is to say, for less cost, more ADCPs could be mounted along the Jinsha River to offer more broad and detailed data to manage the flood.

7. How to Select the Appropriate Equipment for Measuring Current?

According to the Jinsha River, various factors must be kept in mind when it comes to the selection of proper equipment for current measurement. Firstly, according to the type of measurement needed, if it is a measurement on the horizontal cross-section, the HADCP should be chosen. In contrast, if it is about a vertical cross-section, then Vertical ADCP will be appropriate.

Frequency also varies for different water depth levels. For example, the 600 kHz ADCP is suitable for water depths within 70 m. If the water depth of the Jinsha River falls within this range and the measurement requirements are within this range, a 600 kHz ADCP should work. Where the water is deeper, such as at over 70 m up to 110 m, a 300 kHz ADCP would be more fitting since it provides more accurate measurement in that depth.

Some popular manufacturers of ADCPs include Teledyne RDI, Nortek, and Sontek. However, for a low-cost solution, the best option is the China Sonar PandaADCP. The entire body is made of titanium alloy material for ensuring the product is durable and reliable in the water environment. Moreover, it provides an amazing cost-performance ratio. For further information, please refer to: https://china-sonar.com/.

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