How to Measure the Water Current of the Liard River

1. Where is the Liard River?

The Liard River is one of the major rivers in northwestern Canada. It originates in the northern Rocky Mountains of British Columbia and flows to the Yukon Territory.

The river makes its way through the great and very remote wilderness that comprises boreal forests, muskegs, and tundra types of landscapes. It forms a part of the key natural features in this area. It supplies water along its stream for many different animal species. Moose, caribou, and wolves depend on the Liard River for their drinking water. The riverbanks are also habitats for various bird species, such as bald eagles and ospreys.

The Liard River serves as one of the basic transport ways in this sparsely populated area. Historically, it was one of the main water routes taken by fur traders and indigenous peoples. Nowadays, the river still provides access to remote communities and camps. Besides, it hosts a fishery, which includes species such as Arctic grayling and northern pike.

2. What is the flow rate of the Liard River like?

The Liard River discharge shows seasonal and climatic fluctuation. During the spring and early summer, snowmelt from the Rocky Mountains leads to significant increases in the flow of the river. As the snow and ice melt, a large volume of water moves downstream and results in a relatively high-flow period.

During the late summer and fall, the influence of snowmelt declines, and the precipitation patterns turn slim. Still, the river keeps up a base flow which sustains aquatic life and aids in all activities of the local communities or wildlife living in the area. During winter, the flow rate may be reduced further. If it gets very cold, parts of the river may freeze over. The average flow rate has been known to vary from a few hundred cubic meters per second during the low-flow periods up to several thousand cubic meters per second during the peak of the spring snowmelt.

3. How to measure water current of the Liard River?

Velocity Meter Method

In this conventional technique, mechanical or electronic velocity meters are used. These devices are placed at various points on the river to directly measure the velocity of the water in that part. But for a proper understanding of the general trend of the water current, several measurements must be taken from different depths and over different sections of the river. With the length and challenging, oftentimes remote conditions of the Liard River, this could be a very labor-intensive and time-consuming approach.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP profiler is a more sophisticated and handy means of measuring water currents. The ADCP flow meter detects the movement of water particles using sound waves. By emitting acoustic signals and analyzing the Doppler shift of the reflected signals, it can measure the velocity of water at multiple depths simultaneously. This will give a very thorough profile of the water current, enabling more accurate assessment of flow conditions throughout the river. ADCPs can be mounted on boats - where the river is navigable, bridges (if available), or deployed on buoys for continuous monitoring.

Buoy Method

In the buoy method, buoys with sensors to measure the movement of water around them are placed along the river. These buoys float on the surface and can provide some indication of the surface current. In capturing the full complexity of water current, it may not be as good as the other methods, especially for understanding velocity variation at different depths.

Among these methods, the ADCP current profiler stands out as a more sophisticated and efficient option for measuring the water current of the Liard River.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. An ADCP sends an acoustic signal into the water. The sound waves travel in water and interact with moving water particles. Due to the movement of the water particles, because of the Doppler effect, the frequency of the reflected sound waves will change.

If the water particles are moving towards the ADCP current meter, the frequency of the reflected wave will be higher than the emitted frequency. In contrast, if the water particles are moving away from the ADCP, the frequency of the reflected wave will be lower. By accurately measuring this shift in frequency, the ADCP can determine the speed of the water particles at specific depths.

The ADCP then combines these individual velocity measurements at varying depths to provide a complete profile of the water current. In such a way, it becomes possible to have a detailed realization of how the water is flowing, not only at the surface but through the vertical section of the river.

5. What is needed for high-quality measurement of the Liard river currents?

Since this is a high-quality measurement for Liard River currents, the measured equipment should possess some essential characteristics.

The equipment to be used for taking measurements must possess a high degree of material reliability. This is because it will be exposed to the harsh water environment that might involve exposure in water, sediment, and variable temperature. In this regard, the Liard River variable flow and ice and debris during the high-flow and freeze-thaw periods also demand durable equipment.

A small size, light weight, and low power consumption are desirable. A compact and lightweight device is easier to handle and deploy, especially in the remote and often challenging Arctic - like conditions of the region. Low power consumption ensures that the equipment can operate for extended periods without the need for frequent battery replacements or access to a continuous power source.

Yet, cost-effectiveness is of prime relevance. The cheaper an option, the wider usage of the measurement equipment for monitoring can be done on a river.

For casing the ADCP, titanium alloy is one of the best choices. It provides very high resistance to corrosion, which is an essential factor in dealing with water bodies like Liard River, where every moment in operation the equipment is in contact with water and other substances that may be corrosive. It is strong, durable, and capable of resisting physical impacts and changes in pressure during deployment and actual operation. This, together with the relatively low density of titanium alloy, contributes to the overall objective of making the equipment lightweight.

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

The selection of correct equipment for measurement of the Liard River current has several things that have to be taken into consideration.

Based on the Purpose of Use

An HADCP should be the choice if the intention is the measurement of a river current's horizontal cross-section. HADCPs are fully adapted to the job of accurate measurement in the plane of the water flow and help in the understanding of the overall water movement across any particular section of the river.

If the focus is on measuring the vertical cross - section of the river current, a vertical ADCP should be selected. Vertical ADCPs can accurately measure the velocity of the water at different depths and provide a very detailed profile of how the water is flowing vertically within the river.

Based on Frequency

The choice of frequency depends on the depth of the water in the Liard River. A 600 kHz ADCP would normally be quite adequate for waters as shallow as 70 meters. The 600 kHz frequency provides good resolution and accuracy in measuring the current in relatively shallower waters.

It is recommended that for waters deeper than 70 meters up to about 110 meters, it is more appropriate to use a 300 kHz ADCP. Its lower frequency of 300 kHz can better penetrate water deeper and still yield reliable measurements of the water current.

There are known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective option with excellent quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, ensuring durability and reliability. With its remarkable cost - performance ratio, it provides a great alternative for measuring the water current of the Liard River. 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.