Measuring the water current of the Kuskokwim River

1. Place of the Kuskokwim River

The Kuskokwim River is situated in southwest Alaska. It is a major river that has its source in the Kuskokwim Mountains. The river flows into a really extensive and remote wilderness composed of tundra, boreal forests, and marshy lowlands.

This river is quite important to the indigenous Alaskan people who live throughout the region. It's a very major transportation route, particularly within the several ice-free months, where boats are utilized to gain access completely into or out of most communities. The Kuskokwim River is also a vital food supply for the area, especially in its fish resources, such as salmon, whitefish, and pike. Among the inhabitants of these riverbanks are moose, beavers, and many species of birds. The floodplains and wetlands that accompany this river are very important in maintaining ecological balance within the region.

2. Flow Rate Characteristics of the Kuskokwim River

The flow rate of the Kuskokwim River has significant seasonal and climatic variations. During the spring and early summer, the flow increases due to the snowmelt from the surrounding mountains and the thawing of permafrost in the region. The melting ice and snow send a big volume of water downstream, resulting in a relatively high-flow period.

During the fall and winter, there is reduced flow rate. At times, during the coldest months, the river may totally freeze up. In this case, the flow characteristics may change completely by the existence of ice cover. The average flow rate may be few cubic meters per second at low-flow winter to a few hundred cubic meters per second at the peak of the spring snowmelt.

3. Methods to Measure the Water Current of the Kuskokwim River

Velocity Meter Method

This conventional method applies mechanical or electronic velocity meters. Devices are stationed at certain points in the river for direct measurement of the speed of water at respective locations. However, at the Arctic, under harsh conditions and the elongated state of the Kuskokwim River, it is a difficult and time-consuming process to make various measurements at different depths and across sections to fully comprehend the water current.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter is an advanced and more efficient method of measuring water currents. It relies on the use of sound waves to detect movements of water particles. Thus, this type uses an acoustic signal emitted and the Doppler shift of its reflected signal analyzed to measure velocity at several depths simultaneously. This gives a very accurate profile of the water current and thus the flow conditions in the entire river can be assessed with better precision. ADCPs can be installed on boats in cases where the river is navigable, on bridges if available, or on buoys for continuous monitoring.

Buoy Method

In the buoy method, buoys are put in the river, which are fitted with sensors to obtain a record of the movement of water around them. Floating on the surface, these buoys give a signal about the current along the surface. However, they may not be able to capture the full complexity of the water current as well as the other methods can, especially when it comes to knowing the variation in velocity at depths.

Of these, the ADCP current profiler is the most advanced and effective means of obtaining a measurement of the water current of the Kuskokwim River.

4. Working of ADCPs Using the Doppler Principle

The principle that finds application here is the Doppler principle. In operation, an Acoustic Doppler Current Profiler (ADCP) would send out an acoustic signal into the water. The sound waves travel through the water, interacting with moving water particles. Because the water particles are in motion, the frequency of the reflected sound waves is changed by the Doppler effect.

The frequency of the reflected wave will be higher than that emitted if the water particles are moving towards the ADCP doppler. On the other hand, it will be lower if it is moving away from the ADCP profiler. By accurately measuring this shift in frequency, the ADCP can determine the velocity of the water particles at different depths.

Individual velocity measurements by the ADCP meter are then combined at various depths to create a complete profile of the water current. This gives a very good insight into how the water is flowing, not only at the surface but also through the vertical section of the river.

5. Requirements for High - Quality Measurement of the Kuskokwim River Currents

The equipment to be used for high-quality measurement of the Kuskokwim River currents should have the following characterizations.

The materials used in the equipment should be highly reliable. The equipment should be resistant to the severe Arctic conditions of extreme cold, ice impacts, and water and sediment exposure. In regard to the flow variability of the Kuskokwim River and ice floes during freeze-thaw cycles, the deployed equipment must be robust.

It should be small in size, light in weight, and of low power consumption. A compact and lightweight device is easier to handle and deploy, especially in the remote Arctic environment. The low power consumption ensures that the equipment can operate over a long time without needing frequent battery replacement or access to continuous power.

Cost-effectiveness is another key factor. The lower the cost, the wider the usage for measurement tools to carry out wider monitoring of the river.

This is where the casing of the ADCP meter can be effectively made from the alloy of titanium. Another important property of the titanium alloy is its high resistance to corrosion, which is very important in dealing with water bodies like the Kuskokwim River, where the equipment will interact directly with water and other possible corrosive substances. It is also strong enough, durable to resist mechanical impacts, and pressure changes that may occur during deployment and operation. Besides that, titanium alloy has a relatively low density, contributing to the overall goal of keeping the equipment lightweight.

6. How to Choose the Right Equipment for Current Measurement

With so many items on sale to measure the current of a river such as Kuskokwim, careful consideration needs to be made in choosing just the right one.

Based on the Purpose of Use

When the intention is to measure the horizontal cross-section of river current, then a Horizontal ADCP doppler, otherwise known as HADCP, is what should be used. HADCPs have the capability to offer very accurate measurements of water flow in the horizontal plane, which offers an indication of the overall movement of water across a particular section of the river.

If the interest is in measuring the vertical cross-section of the river current, a vertical ADCP current profiler is to be used. The water speed is correctly measured by Vertical ADCPs at various depths to produce a detailed profile of how the water flows in a vertical sense within the river.

Based on the Frequency

The choice of frequency depends on the depth of water in the Kuskokwim River. In general, a 600 kHz ADCP will suffice for water depths of up to 70 meters. The frequency of 600 kHz gives good resolution and nice accuracy over the water current in such relatively shallow waters.

For deeper waters like above 70 meters up to approximately 110 meters, a 300 kHz ADCP will be more appropriate. The 300 kHz lower frequency can go deeper into the water and still give good measurements of the water current.

There are popular ADCP current meter brands such as 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 Kuskokwim 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.