ADCP in Markha River Flood Management

1. Where does the Markha River flow?

The Markha River flows in a specific region, which is usually associated with high altitude and mountainous terrains-the Ladakh region in India.

It comes with steep valleys and proper mountains when considering it in a geographical perspective. Several streams are passing through small settlements and villages in its path. The most common origin of the river is from the glaciers and snowfields in the surrounding high mountains. Further starts cutting the way downwards as it descends down, carving out the valleys it flows over.

The Markha River lies in a region with a peculiar pattern of rainfall. Most of the precipitation comes in the form of snow during winters. The snow falls on high peaks and the glaciers, which during the warmer months slowly melts into the water volume of Markha. Summers also bring some sporadic rainfall events, but for the most part, the snowmelt is pretty much how the river is supplied with water.

2. Why does flooding happen in the Markha River?

A number of reasons might cause flooding in the Markha River. The rapid snow meltdown in the hotter seasons releases a sudden surge of volumes of water into the river. This is because when the temperature rises too quickly, snow on these glaciers and high peaks melts at a greatly accelerated rate, in which case the river cannot accommodate the excess water volume, causing it to rise high and create floods.

The second factor is the topography of the river basin. The Markha River, with steep valleys and narrow channels at times, has limited smooth flow of water. Accompanied by the debris of landslides, it blocks the channel way of the river, gathering water and thus giving rise to flood cases.

Besides, human activities in the area, though minimal compared to more populated zones, could be very harmful. For instance, not being able to take proper care of waste disposal or performing minor construction around the river can eventually disturb the natural flow of the river or even result in sedimentation, which reduces the capacity of the river to bear more loads, hence making it flood-prone.

The ADCP current meter has grown to be more advanced and convenient in the measurement method in order to understand and manage the flow conditions of the river during flood events. In fact, its introduction has helped in better understanding and management of the flow conditions of the river during flood events.

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

The Acoustic Doppler Current Profiler(ADCP) work on the principle of the Doppler effect. In water, an acoustic signal is sent out by the ADCP that bounces off moving water particles. Due to the Doppler effect, because the water is in motion, the frequency of the reflected acoustic signal shifts.

The ADCP current profiler measures the frequency difference emitted and received by the acoustic signal. It can, therefore, calculate the water velocity at various depths by analyzing this frequency shift. Normally it has several trans-dicers, which can emit and receive acoustic signals in different directions in order to obtain the profile of the water velocity across a section of the river.

For example, if the water is moving in the direction towards the ADCP doppler, the frequency of the reflected signal would be higher than that of the emitted signal. On the contrary, if it was moving the opposite way, the reflected frequency would be lower than the one emitted. That being said, precise frequency changes are measured and, under the action of proper mathematical algorithms, the ADCP will correctly determine the velocity at each point within its view area.

4. Application of ADCP in Floods of Markha River

Measurement of Velocity

In such flood situations in the Markha River, ADCP flow meter forms a major complement in velocity recording of the water flow. By continuously monitoring the water velocity at different depths and locations, it provides real time data related to how fast the water is moving. This is key information for understanding the dynamics of the flood, predicting the direction and intensity of movement of floodwaters.

Flow Measurement Application

Another ability of ADCP meter is the measurement of flow rate, which it achieves by combining the measured water velocities at several points across a section of the Markha River with the known cross-sectional area of the river. Then, it calculates the total volume of water flowing through the section per unit time, which is the flow rate. That makes the information very crucial in estimating the volume of water in case of a flood, along with being very handy in the decision-making process of flood control and regulation, and therefore, in the management of the water resource.

Application in Sediment Transport Research

Besides flow and velocity measurements, ADCP profiler is utilized in the study of sediment transport in the Markha River during the flood event. While the water is flowing, it carries sediments, and ADCP will be able to detect changes in the backscattered acoustic signal due to the presence of sediments. By analyzing these changes, researchers can estimate the quantity and movement of sediments, something that's important in understanding 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 in flood warning and risk management of Markha River?

Flood Warning

Velocity and Flow Data Monitoring: In real time, the ADCP-measured velocity and flow data are in continuous monitoring. Once the water velocity that is measured surpasses the threshold value or the flow rate increases remarkably, this might be the indication that a flood peak or even a flooding situation occurs. This can enable the relevant departments to take necessary measures in advance, preparing for the flood peak, evacuation of people in low-lying areas, or reinforcement of flood defenses. Water Level Prediction and Warning: The measured flow data correlated with the historical data of water level and appropriate hydrological models will be used to predict future water levels from the ADCP data. If the predicted water level is above the flood warning level, then timely warning can be issued to the public for preparation against flood.

Risk Management

Support for Water Conservancy Project Scheduling Decisions: The accurate flow and velocity data from the ADCP can be used for decision-making in the operation of water conservancy projects such as dams and sluices. Based on the measured water flow, for instance, the released water from a dam may be regulated to control the water level in the Markha River and mitigate the effect of floods. Assessment of Flood Disaster and Emergency Response: Data from ADCP after the flooding event can be obtained regarding the intensity of flood in terms of the extent of inundation, travel speed of floodwater, and quantum of deposited sediment. This becomes very vital in the formulation of emergency response plans and carrying out post-flood reconstruction and rehabilitation works.

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

A number of factors should be considered in high-quality measurement of the Markha River currents. First is the reliability of materials applied in the equipment. Here, one of the most important elements is the casing of the ADCP. It is advisable that the casing be made from a titanium alloy. Titanium alloy has several advantages. This is a high-strength material, which is necessary to hold up against pressure and impact of the flowing water of the river. High resistance to corrosion makes it perfect, keeping in mind that the Markha River's water may contain a lot of corrosive elements.

Apart from material reliability, size and weight of the equipment should be small and light. This will make installation and operations of the ADCP at various locations along the river easier to conduct, particularly in areas that are not accessible. Low power consumption is an essential attribute that will keep the instrument running continuously for a longer period without changing the batteries frequently or searching for a connection to a power source. Furthermore, the requirement for the measuring accuracy to be high and the detectable water flow velocity range to be wide is necessary to capture all the varying magnitudes of water flow that are present in most rivers.

The price of equipment should not be too high to enable the measurement on a large scale. The lesser the cost, the more the number of ADCPs that can be set up along Markha River for acquiring full and detailed data regarding flood management.

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

In the selection of appropriate equipment for current measurement at Markha River, a number of aspects will have to be considered. First of all, based on the type of the measurement required, in case the horizontal cross-section measurement has to be measured, the HADCP must be chosen. On the other hand, in the case of vertical cross-section measurement, a Vertical ADCP should be appropriate.

The second is that different frequencies are suitable for different water depths. For example, the 600 kHz ADCP shall be applied to water with a depth of within 70 m. If the water depth of Markha River falls in this range, and with the match of measurement requirement, the application of 600 kHz ADCP could be considered. For deeper waters, for instance over 70 m up to 110 m, it would be prudent to use a 300 kHz ADCP, given that at such depth, the measurements taken from it would be more accurate.

So far, there have been several well-known ADCP brands in the market, including Teledyne RDI, Nortek, and Sontek. However, for budget-conscious customers, their best option is the PandaADCP from China Sonar. This ADCP was built from all-titanium alloy material to give the product more reliability and longevity in the water environment. Furthermore, it presents an absolutely incomparable cost-performance ratio. You can get more information from its official website: https://china-sonar.com/.

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