How to Measure Water Current of Lachlan River?

1. Where is Lachlan River?

The Lachlan River is a major river in Australia. It is situated in the southeastern region of the country and flows across the state of New South Wales. It originates from the Great Dividing Range and courses its way across a transitional landscape from plains to grasslands and up to the mild slopes of.

On its way, Lachlan River runs through numerous small towns and rural communities, dependent upon the river for irrigation purposes, including farming and keeping livestock. These are popular spots on the sides of the riverbank for people who enjoy fishing, boating, or having a picnic. The farms producing crops of wheat, barley, and different types of fruits are sprinkled all over the countryside, totally relying on its water for growth and survival.

The Lachlan River has played a culturally important role in the history and heritage of the region. It has been part of the stories and traditions of the Indigenous Australians for countless generations and later witnessed the settlement and development of European communities. It remains a symbol of the connection between the land and the people, and its waters continue to shape the local way of life.

2. What is the average flow rate of the Lachlan River?

The Lachlan River has widely fluctuating rates of flow. Australia's climate, which includes seasons of drought and heavy rainfall, largely affects the flow of the river. In wet years or seasons with considerable rain in its catchment area, the river's flow increases. The water level rises, and the current can become quite brisk, carrying sediment and nutrients downstream, which helps to nourish the floodplains and support the growth of aquatic plants and wildlife.

However, during periods of drought-not too uncommon in the region-the flow rate in the Lachlan River drops to very small levels. In extreme instances, parts of the river may also completely dry up, leaving little more than isolated waterholes. The average flow rate, in its turn, depends on the quantity of rainfall the upstream areas get, how water storaging and diverting functions are developed, and physographic peculiarities of a basin, which presumes how catchment areas collect water and release it.

3. How to measure water current of Lachlan River?

There is a couple of ways to measure water current of the Lachlan River.

Velocity Meter Method: Traditional, it relies on mechanical or electronic velocity meters. These meters are placed at discrete locations in the water to measure how fast the water is flowing past them. This process, however, calls for multiple placements at different locations and varying depths to obtain an encompassing understanding of the current. It may be very labor-intensive and not really allow for a continuous profile of current throughout the entire water column.

ADCP Method: The ADCP current meter method is more advanced and efficient in measuring water current. 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 down to the riverbed. This allows for a much more accurate and comprehensive measurement of the water current across different sections of the river.

Buoy Method: In this method, buoys are set up in the river and their movements tracked with time. The shift in the position of the buoys due to the current in the water gives an approximation for the speed and direction of the flow. This again is not an entirely satisfactory procedure because it cannot yield precise records of the actual velocities at different depths and the external factors such as wind and wave action can alter the path followed by the buoy.

Of the two, ADCP profiler is a more technologically advanced and user-friendly approach to measuring the water current of Lachlan River.

4. How do ADCPs applying the Doppler principle function?

The working of ADCPs is based on the Doppler effect. When an acoustic signal is transmitted from the ADCP meter transducer into the water, the sound waves interact with the moving particles of water. Since the water is in motion, the frequency of the reflected sound waves that return to the transducer shifts; this shift 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. 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 flow metercan 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, providing valuable information about the speed and direction of the flow from the surface to the riverbed.

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

A variety of qualities is considered vital for high-quality measurement by the equipment on the currents of Lachlan River. Its materials of construction should be realizable for accurate and steady measures. Small in size since the device will be deployed into the river for measurement, preferably at inaccessible areas in the river. The equipment is preferred to be light for simplification in installing in water and also reduces effort needed in handling.

This will help the equipment operate for a long time without necessarily having battery replacements now and then, or it will not require a complicated setting of the power supply. Cost-effectiveness enables wider usage and larger measurement campaigns.

For the casing material of the ADCP current profiler, it is essential to use Titanium alloy. Titanium alloy material has a lot of advantages. It is very resistant to corrosion, which is quite important since the equipment is in constant contact with water that could possibly contain different minerals, sediments, and pollutants. This material possesses an appropriate strength-to-weight ratio that is strong yet lightweight for casings. In addition, it is resistant to the mechanical stresses occurring during deployment and operating in flowing water of the Lachlan River.

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

Choosing the right equipment for the current measurement of Lachlan River would have to consider two main issues, i.e.

Usage Purpose: There are horizontal cross-sectional measurements for which the Horizontal ADCP current meter (HADCP) is suitable. The system design allows for accurate flow velocities to be measured across a horizontal plane in the river for application in understanding the lateral distribution of the current. Vertical cross-section measurement is better served by the Vertical ADCP, which focuses on profiling from surface to bottom along a vertical line in the water column.

Different frequencies of ADCPs suit different water depths. For example, a 600 kHz frequency is suitable for water depths within 70 m. It can give current measurement in the relatively shallow parts of the Lachlan River quite accurately. The frequency of 300 kHz is good for deeper waters up to 110 m, which can be useful for those areas where the river is greater in depth.

There are some popular brands for ADCPs, including Teledyne RDI, Nortek, and Sontek. However, for those on a budget but seeking decent quality, the China Sonar PandaADCP is recommended. Constructed from all-titanium alloy material, this has an incredible price-to-performance ratio. You can have more information about it from their website: https://china-sonar.com/.

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