How to Measure Water Current of the Arkansas River?

1. Where is the Arkansas River?

The Arkansas River is one of the major rivers of the south-central part of the United States. It begins in the Rocky Mountains in Colorado, twisting and turning through Kansas, Oklahoma, and Arkansas, ending with its mouth into the Mississippi River.

In Colorado's high country, the Arkansas rises among granite peaks and alpine meadows within the Rockies. The cold, limpid flow is fed throughout by snowmelt and mountain springs. Right through arid plains in Kansas, it courses to form a vital agriculture water supply. The farms and ranches are on opposite banks, while its waters also supply irrigation, thus sustaining crops such as wheat and corn.

The Arkansas River meanders through lively cities like Tulsa and Little Rock. Along its course, urban areas have grown, and it has played an important role in the history and building of the cities. It is considered a famous place for recreation in boat trips, fishing, and white-water rafting. The Arkansas River, with its mix of woodlands, wetlands, and floodplains, provides a home for both Oklahoma and Arkansas, offering such wildlife as deer, beavers, and several varieties of waterfowl.

2. What does the Flow Rate feature of Arkansas River look like?

There is dramatic variation seasonally, as well as geographically, in the flow rate of the Arkansas River. During spring, because of snowmelt from the Rocky Mountains, it rises very rapidly. The river swells, and the current gets quite powerful. This period of high flow is very important in replenishing reservoirs and for the overall health of the river's ecosystem.

During the summer months, this flow rate could vary with precipitation and water use for irrigation. In dry years, flow is reduced, but in wet years, it stays high. The onset of autumn generally begins to reduce the flow rate. Flow is usually at its lowest during the winter months, but still maintains a base flow due to the contribution of groundwater and release of water from upstream reservoirs.

As can also be seen in the graph, the average flow rate fluctuates with the length of the river. Closer to the mountains in the upper reaches, the flow is usually more rapid due to the steeper gradient. While entering the flatter regions of the plains and heading toward the Mississippi River, it is slowed and the river widens.

3. How to Measure Water Current of the Arkansas River?

There are many ways to measure the water current of the Arkansas River.

Traditional Methods

Float Method: The most basic, simplest, and traditional method of estimating the water current is by using a float. A buoyant object such as a block of wood or plastic bottle is used and set free in the river. It allows for an approximation in the speed of surface current, as it measures the time it takes the float to travel a known distance. This is not a perfect method, because several sources of error exist: wind and wave actions may either retard or hasten the progress of the float; the float itself may be imperfectly streamlined. Moreover, it gives only the surface current; it does not give the current at higher or lower levels. 

Current Meters: Mechanical or electronic current meters for the speed of water at one point are available. These are placed in the water at some depth and record the speed of the water that passes through them. They give more accurate measurements than the float method at a single point in the water column. Yet they are limited to that depth and also do not show the entire current profile throughout the water column.

Advanced Approach: Acoustic Doppler Current Profiler (ADCP), ADCPs are a more advanced and efficient way to measure the water current of the Arkansas River.

3.1 How Do ADCPs Using the Doppler Principle Work?

This principle applies to ADCP-the Doppler effect. An acoustic pulse is produced from the device and sent into the water. Reflected acoustic signals change in frequency due to water movement through interactions with the particles and any other substances suspended in the water, which may include sediment, plankton, and other small pieces of debris. 

The ADCP measures this frequency shift and, using the Doppler formula, calculates the velocity of the water at various depths. Because the ADCP sends out pulses in several directions and at various frequencies, a finely detailed profile of the current of the water throughout the water column is generated. This provides a much more complete understanding of the river's current structure than traditional methods, which only measure at the surface or one point in the water column.

3.2 What do we need so that we can see the best quality Arkansas River current measurement?

 To get fine quality measurement of the current of the Arkansas river, the devices must be highly reliable. As there is vast variation in weather and water quality in the river, from flood, draughts to sediment-carried water, the measuring devices must be resilient enough to survive these tests. 

The equipment should be comparatively small in size and lightweight. This will be important for ease of deployment, especially in remote areas along the river or from boats. The power consumption should be low in order to enable the equipment to operate for as long as possible without frequent changes of batteries or external power supply. Finally, cost-effectiveness is another crucial factor, especially when large-scale or long-term measurements are needed to monitor the dynamics of the river. 

The casing of ADCPs is made using the already developed and favorable material of titanium alloy. Titanium alloy is a highly resistance material to corrosion, essential in the water-rich environment of the Arkansas River. If other materials are exposed to constant water, with the presence of several active chemicals and sediments within the water, they are sure to corrode fast. The toughness and durability of the titanium alloy are also enough to resist the physical forces of the river current and possible impacts from floating logs or other debris. Being light in weight, it is more convenient for installation and transportation.

3.3 How to Choose the right equipment for current measurement?

During the choice of equipment for measurement of the Arkansas River Current, there is a need to consider the requirements entailed by the measurement. 

For horizontal measurements across the section of the river, HADCP is appropriate. It gives a wide visual outlook across the current flow horizontal plane, useful in acquiring a glimpse into the general flow patterns of the river. This is particularly essential in view of the study of water and sediment circulation across the river and the influence of the current on navigation and nutrient distribution. 

Vertical ADCP is more applicable for vertical profile measurements of current. It provides finer resolution of water velocity at each different depth, and such information is crucial in studies concerning stratification and mixing of the water column. Again, this is highly useful in understanding the distribution of properties such as oxygen and temperature and the behavior of organisms in the water. 

Frequency Selection: A frequency of 600 kHz for an ADCP could work for the relatively shallower sections to about 70 meters of the Arkansas River; in deeper parts, to about 110 meters, the choice falls on 300 kHz for an ADCP. The depth of water and resolution in current profile desired determines the frequency selection.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with good quality, the ChinaSonar ​PandaADCP is a great choice. It is made of all - titanium alloy, providing durability and resistance to the Arkansas River's environment. It also offers an excellent price - performance ratio. You can visit ​https://china-sonar.com/ for more information.

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