How to Measure Water Current of Finlay River?

1. Where is Finlay River?

The Finlay River is an important river in British Columbia, Canada. It happens to be in the north of the province and runs as a major tributary into the Peace River system. The source of this river lies in the mountains of the northern Rockies.

It flows through areas of boreal forest and mountain valleys as it winds its way along the landscape. The Finlay River forms a very vital habitat for a wide variety of wildlife. It contains various fish species, including salmon and trout, which are integral parts of the local aquatic ecosystem. Small communities and First Nations settlements can be found on its banks. The local people have a long-standing relationship with the river, dependent on it for fishing, transportation, and as a source of water for domestic and traditional activities.

Culturally, the Finlay River means everything to the First Nations. It is part of their history, their tradition, and their spirituality. Very often, it forms an integral part of stories that are told or even ceremonial issues, representing connections with this land and ancestors.

2. What does the flow rate of the Finlay river look like?

The Finlay River undergoes variations in flow rate seasonally. In spring, snowmelting in the surrounding mountains significantly increases the flow in the river. The level of water increases, and the current is quite powerful. This is an essential time for sediments and nutrients to be transported downstream by the flow, enriching the floodplains and ecosystems associated with the river.

During the summer, it stabilizes to a degree. Nevertheless, it still maintains the same amount of water provision for the local communities' needs and the wildlife's survival. The flow within the river is sustained from a combination of rainfall catchment area and the repletion of groundwater. During the fall and winter seasons, the flow rate decreases. This average flow rate depends on a number of factors that include the quantity of snowfall in the catchments, the nature of topography of the river basin regarding catchment and drainage, and the utilization pattern by the local communities.

3. How to measure water current of Finlay River?

There are a few ways of measuring the water current of the Finlay River.

Velocity Meter Method

The traditional practice relies on mechanical or electronic velocity meters. Those meters are placed at discrete positions in the water and gauge the speed of the flowing water. However, when trying to get a clear picture of the current at hand, multiple placements both in space and depth require a great deal of effort. This can be extremely time-consuming and may lack a continuous profile of the water column for the current display.

Acoustic Doppler Current Profiler (ADCP) Method 

The ADCP current meter method of measurement is advanced and efficient. It uses sound waves to measure the velocity of water at different depths simultaneously. By emitting acoustic signals and analyzing the Doppler shift of the reflected signals, it can create a detailed profile of the current from the surface to the riverbed. This gives a very accurate and comprehensive measurement of the water current across different sections of the river.

Buoy Method

This is done by installing buoys in the river and observing displacements with time. Movement of buoys through the water current indicates a sense of speed and flow direction. However, some of the disadvantages include potential inaccuracies in measuring current velocities at different depths or influence of external factors that might affect the buoy motion, such as wind and ripples.

Among these methods, the ADCP current profiler method is more advanced and convenient for measuring the water current of the Finlay River.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. An acoustic signal is sent from the ADCP meter transducer into the water, and the sound waves elastically scatter off the moving water particles. The frequency of the reflected sound waves back to the transducer changes due to the flowing water, which is called the Doppler shift.

If the water is moving towards the transducer, then the frequency of the reflected waves will be higher than the emitted frequency. In case the water is moving away from the transducer, the frequency will fall. By precisely measuring this frequency shift at multiple angles and depths, the ADCP profiler can calculate the velocity of the water in various directions and at different levels within the water column. This enables it to create a detailed profile of the water current, providing important information about the speed and direction of the flow from the surface to the riverbed.

5. What's needed for high - quality measurement of Finlay river currents?

For high - quality measurement of the Finlay River currents, the measuring equipment should have certain characteristics. The materials used in its construction need to be reliable to ensure accurate and consistent measurements. A small size is beneficial as it allows for easier deployment and retrieval in the river, especially in areas with difficult access. The equipment should also be lightweight to simplify the installation process and reduce the effort required for handling.

Low power consumption is one of the key factors to ensure equipment can run for a very long period without frequent replacements of the battery or complex power supply set up. Cost-effectiveness is yet another major factor because more widespread usage and larger-scale measurement campaigns could be possible this way.

In the case of ADCP current meter casing, one of the best materials will be a titanium alloy. Titanium alloy has many advantages. It is highly resistant to corrosion, which is important because the equipment is always in contact with water that could contain many minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, enabling a strong yet light casing. It will also be able to resist mechanical stresses during deployment and operation in flowing water in the Finlay River.

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

In choosing the right equipment for measuring the current of the Finlay River, two main factors should be considered.

Depending on the usage purpose, for horizontal cross - section measurement, the Horizontal ADCP (HADCP) is the suitable option. The measurements have been made to survey with reasonable accuracy the flow velocities over a horizontal plane in the river; such is useful to get a clear picture about the current distribution laterally. The Vertical ADCP should, on the other hand, be appropriate for vertical cross-measurement because it faces in the direction of profiling of the current from the surface to the bottom along a vertical line in the water column.

Second, different frequencies of ADCPs suit different water depths. For instance, an ADCP current profiler of 600 kHz frequency is suitable for water depths within 70 m. It can provide accurate current measurements in the relatively shallower parts of the Finlay River. An ADCP with a frequency of 300 kHz is more appropriate for deeper waters up to 110 m, which may be useful in areas where the river has greater depth.

There are well - known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with good quality, the China Sonar PandaADCP is highly recommended. It is made of all - titanium alloy material and offers an incredible price - performance ratio. You can find out more about it on its website: https://china-sonar.com/.

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