How to Measure Water Current of Missouri River?

1. Where is Missouri River?

The Missouri River is a mighty, sweeping stream that was destined to be one of the most celebrated of the United States. Its headwaters are in the Rocky Mountains of Montana, and its course takes it across America's heartland through many varieties of terrain: vast flat plains, rugged canyons, and rich farming communities.

It is the lifeblood for many cities and towns along its course, starting from Bismarck in North Dakota to Kansas City in Missouri. These urban centers rely on the Missouri River for various purposes: it avails them with an essential supply of water for drinking, industrial use, and irrigation of agricultural fields. The surrounding plains are home to extensive farming operations, with crops such as corn, soybeans, and wheat being cultivated with the help of the river's water.

The Missouri River has more cultural history than most rivers. This was a transportation route and thoroughfare for early settlers and Native American tribes alike. The Lewis and Clark Expedition followed the Missouri River in their exploration of the western frontier of the United States. Historical sites and remnants of old civilizations line the banks of this river, and its stories and legends have been passed on down through the ages.

2. What is the nature of the flow rate in the Missouri river?

The Missouri River has a highly variable flow rate. The seasonal changes are significant. During the spring, the snowmelt from the Rocky Mountains and other upstream areas causes a large rise in the flow of the river. The water level rises, and the current becomes strong and turbulent. This period is also important for sediment transport and floodplain inundation, which enriches the surrounding agricultural land.

In the summer and fall, it settles down somewhat, but flow still varies with rainfall and with water management such as dam releases. It is lower in the winter, but generally does not freeze up completely. The average flow rate depends upon various factors like the amount of snowfall in the upstream areas, topography of the river basin which affect the collection and runoff of water, and working of large no. of dams and reservoirs on the river.

3. How to measure water current of Missouri River?

There is mainly following ways to measure water current of Missouri River:

Velocity Meter Method

This traditional approach makes use of mechanical or electronic velocity meters. These meters are placed at specific points in the water to measure the speed of the water passing by. However, to get a comprehensive understanding of the current, multiple placements at different locations and depths are necessary, which can be very time-consuming and may not provide a continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) is an advanced and efficient way of measuring water current. It applies sound waves to measure the velocity of water simultaneously at different depths. 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 therefore provides the actual and comprehensive measurement of water current across different sections of the river.

Method of Buoy

In this, buoys are placed in the river, and their movements are traced over some time. The movement of these buoys due to water current is indicative of the speed and direction of the flow. This method does have its limitation: not being able to yield correct velocity at different depths and errors due to factors such as wind and wave action influencing the buoy's movement.

Among these methods, the ADCP current profiler method is more advanced and convenient to measure the water current of the Missouri River.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. When an acoustic signal is transmitted from the ADCP flow meter transducer into the water, the sound waves encounter and interact with the moving particles of water. Since the water is in flow, the frequency of the reflected sound waves back to the transducer shifts, now called the Doppler shift.

If the water is moving towards the transducer, the frequency of the reflected waves will be higher than the emitted frequency. If the water is moving away from the transducer, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and depths, the ADCP current profiler can calculate the velocity of the water in different directions and at different levels within the water column. This enables it to create a detailed profile of the water current, and it provides very valuable information on the speed and flow direction from the surface of the water right to the bed of the river.

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

Measurements of the currents of the Missouri River demand equipment with a particular characteristic to result in quality. The materials from which it is made must be dependable for correct and reproducible readings. The size should be small enough for ease of deployment and retrieval into the river and specifically for those places where the area is not accessible. The equipment also should not be too heavy for easy installation and to minimize labor in manipulating it.

It needs to consume low power so that it could run for several hours, not requiring frequent replacements of the batteries or a heavy arrangement for powering. Cost-effectiveness allows for wider applications and for large-scale measurement campaigns.

For the ADCP profiler casing, one can take up the titanium alloy as a superior option. Many are the plus points of using titanium alloy. It is very resistant to corrosion, and it should be, seeing how equipment will always come in contact with water with its multitude of minerals, sediments, and pollutants. Then it possesses an excellent strength-to-weight ratio for making durable casings yet not heavyweight, a plus, besides enabling it to withstand mechanical stresses during the instances of deployment and operations along with the flowing water.

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

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

Depending on the usage purpose, the horizontal cross - section measurement is suited to HADCP. It is designed to measure the flow velocities across a horizontal plane in the river with high accuracy, which is useful in understanding the lateral distribution of the current. In the case of vertical cross-section measurement, the Vertical ADCP is more appropriate since it focuses on profiling the current from the surface to the bottom along a vertical line in the water column.

The ADCPs are appropriate for different water depth based on different frequencies, and this may be seen from an ADCP meter at 600 kHz suitable for 70 m. Such an instrument could offer appropriate current measurements from a reasonably shallow area of the Missouri River. However, if the aim is for higher depth-let's say 110 m-an ADCP profiler operating on a 300 kHz frequency is quite suitable for application in the deeper area.

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.