How to Measure Water Current of Culgoa River

1. Where is Culgoa River?

The Culgoa River is in New South Wales, Australia. It forms part of the Murray - Darling Basin. The river rises in the northern slopes of the Warrumbungle Range and flows in a northwest - southeast direction.

As it winds its way through the Australian outback, it crosses semi-arid plains and grasslands. These are habitats for a great number of wildlife, such as kangaroos, emus, and several bird species. It is a vital source of water for these animals, as well as for the scant vegetation of the area. Small rural communities and some agricultural areas are also found along the banks of this river. The local farmers take water from the Culgoa River for irrigation in order to grow wheat and cotton.

The river culturally relates to the history of the region, part of the traditional lands of Indigenous Australians, stories and Dreamtime legends often relate to this river. In turn, European settlers also have a history with the Culgoa River, using it for transportation and water supply in early days of settlement.

2. What does the flow rate of the Culgoa river seem like?

The flow rate of the Culgoa River significantly varies because of the climatic condition of Australia. It flows when there is enough rain in its catchment area during wet years. At this time, the water level will rise, and the current might be strong. This phase is crucial for carrying more sediments and nutrients further downstream, which enriches the floodplains and the adjacent agricultural lands.

However, during droughts-a common occurrence in the Australian outback-the flow rate of the Culgoa River decreases. During severe drought conditions, parts of the river may dry up or have very low-flow sections. These are, of course, influenced by such things as the amount of rainfall in the upstream regions, the topography of the river basin which dictates how water is collected and drained, and even the usage patterns of local communities, especially for agricultural irrigation.

3. How to measure water current of Culgoa River?

There are several methods of measurement of water current of Culgoa River, Those include.

Velocity Meter Method

Traditional approaches in this regard make use of mechanical or electronic velocity meters. Meters are placed at several locations in the water, recording the speed of water flowing past them. To gain a complete understanding of the current, however, multiple placements across different locations and depths are needed. This may be an extremely time-consuming process with no continuous profile of the current throughout the water column.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter method is the more advanced and efficient method of water current measurement, using sound waves to measure simultaneously the velocity of water at different depths. It generates a thorough profile of the current from the surface to the riverbed, by emitting acoustic signals and analyzing the Doppler shift of the reflected signals. In this way, the real measurement of water current across different sections of the river is much more accurate and comprehensive.

Buoy Method

This is done by placing buoys in the river and monitoring their movement over time. Displacements of buoys caused by the current indicate something about the speed and direction of flow. However, it has a lot of disadvantages. The method is usually not effective for giving the exact measurement of the velocity profile along the vertical and horizontal cross-sections, and could also be subjected to the actions of wind and waves that could affect the buoy movements.

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

4. How do ADCPs using the Doppler principle work?

Doppler is the principle of operation of ADCPs. Basically, an acoustic signal transmitted by the ADCP meter transducer into the water interacts with moving particles of water. Due to flowing, the frequency of reflected sound waves back to the transducer changes; this happens in what is known as Doppler shift.

If the water is moving towards the transducer, then 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 profiler calculates the velocity of the water in different directions and at different levels within the water column. It provides a detailed profile of the water current, which gives essential information on the speed and direction of the flow from the surface to the riverbed.

5. What is required for high-quality measurements of Culgoa River currents?

The measuring equipment for the high-quality measurement of currents of the Culgoa River should possess some traits. The materials used to build it should be reliable to make sure that the measurements are precise and consistent. A small size is advantageous because of the ease of deployment and retrieval in the river, especially when access is poor. It should also be lightweight to make the installation process easy and also reduce the amount of effort to handle it.

Such instruments are required to have low power consumption in order to keep the equipment running for months without the need for expensive replacement of batteries or an uncomfortable power supply setup. The cost-effectiveness allows us to use more units in a wider area and makes greater measurement campaigns possible.

From several points of view, a casing material for an ADCP flow meter should be made of titanium alloy. In fact, titanium alloy possesses many advantages. It is highly resistant to corrosion, which is crucial since the equipment is constantly in contact with water that might contain various minerals, sediments, and pollutants. Besides that, it has a good strength-to-weight ratio, thus providing a durable yet lightweight casing. It can also support mechanical stresses during deployment and operation in the flowing water of the Culgoa River.

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

When choosing proper equipment for measuring the Culgoa River's current, there are two main determining factors.

Depending on the usage purpose, for horizontal cross - section measurements, the Horizontal ADCP or HADCP would be appropriate. It is designed for accurate measurement of flow velocities across a horizontal plane in the river, useful in studying the lateral distribution of current. For vertical cross-section measurement, the Vertical ADCP would be more appropriate since it focuses on profiling the current from surface to bottom along a vertical line in the water column.

Second, different frequencies of ADCPs are suitable for different water depths. For example, the ADCP with a frequency of 600 kHz is suitable for water depths within 70 m. It provides accurate current measurements in the relatively shallower parts of the Culgoa River. An ADCP current profiler with a frequency of 300 kHz is more appropriate for deeper waters, up to 110 m, which can 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.