How to Measure Water Current of the Murrumbidgee River?

1. Where is the Murrumbidgee River?

The Murrumbidgee River is one of the main watercourses in Australia. It rises in the Australian Capital Territory, near the city of Canberra. From its source, it meanders down New South Wales, passing through many varying types of lands.

It skirts across the countryside, with much agricultural land dependent upon its waters for irrigation. The river is a lifeline to the farming communities along its banks, allowing the cultivation of crops like wheat, cotton, and various fruits and vegetables. It meanders its way through small towns and villages falling along it, associated with historical and cultural relevance to it.

The Murrumbidgee River has an enormous amount of wildlife in it. There is a very rich aquatic life-there are lots of species of fish, including Murray cod and golden perch. The banks of this river are home to herons, egrets, and ducks. The floodplains and wetlands surrounding it are an important breeding and feeding area for these and other species, adding to the overall biodiversity of the region.

2. What is the Flow Rate of the Murrumbidgee River Like?

The flow rate in the Murrumbidgee River is highly seasonal. During the wet season, that is between October and March, the river inflates with an increased flow rate because of the amount of rainfall that prevails at that period of the year. The water level rises, and at this point in time, the river will be able to carry a large volume. It is a very significant high-flow period that replenishes the storage of water in dams, reservoirs, and other storages along its course and helps in maintaining the health of the downstream ecosystems.

It would follow that in the dry season-which is from April to September-this flow rate decreases. This will keep a base flow necessary for the survival of aquatic life, as well as supplying communities and agriculture with water around it. The average flow can increase from some cubic meters per second in the driest time of the year up to thousands of cubic meters per second during the peak of the wet season.

The navigation capability also depends on the volume of water the Murrumbidgee River carries. In the high-flow period, small boats have little problem traveling in the river, while during the low-flow season, navigations may be restricted.

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

Velocity Meter Method

The traditional method is done by using mechanical or electronic velocity meters. These are placed at certain points in the river to measure directly the speed of water at any one point. However, many such measurements must be taken at different depths and parts of the river if the overall current of the water is to be comprehensively determined. The Murrumbidgee River is long with varying conditions, and this method does tend to be extremely cumbersome and tedious.

ADCP Method

The ADCP current meter provides a rather advanced and also easy way of measurement of water currents. It detects the movement of the water particles by the use of sound waves. By emitting acoustic signals, thereby analyzing the Doppler shift of the reflected signals, it is in a position to measure simultaneously the velocity of water at different depths. This provides a detailed profile of the water current, thus giving full and comprehensive information on flow conditions throughout the river. ADCP current profiler can be mounted on boats, bridges, or even deployed on buoys for continuous monitoring.

Buoy Method

The buoy approach includes buoys in the river tagged with sensors for measuring water movement around them. These buoys float on the surface of the river and provide an outline of the surface current only up to a certain extent. They may not be as comprehensive for the water current as the first two methods, at least with regard to how it varies with depth.

Among these, the ADCP flow meter is one of the modern and efficient methods to measure the water current of the Murrumbidgee River.

4. How Do ADCPs Using the Doppler Principle Work?

The Acoustic Doppler Current Profiler(ADCP) work on the principle of Doppler. When an ADCP meter sends an acoustic signal into the water, the sound waves travel through water and collide with moving particles of water. Since the particles of water are in motion, due to the Doppler effect, the frequency of the reflected sound waves is different from the original.

If the water particles are moving towards the ADCP profiler, then the reflected wave frequency will be higher than the emitted one. In contrast, if the water particles are moving away from the ADCP, the frequency of the reflected wave becomes lower. By precisely measuring this shift in frequency, the ADCP infers an estimate of the velocity of water particles at several depths.

These individual velocity measurements obtained at different depths are then combined by the ADCP to develop a comprehensive profile of the water current. This enables high resolution of how the water is flowing, not only at the surface but in most of the vertical section of the river.

5. What's Needed for High - Quality Measurement of the Murrumbidgee River Currents?

There are a number of critical factors related to the equipment that would measure the currents of the Murrumbidgee River highly effectively.

The material used in the equipment should be highly reliable. It should be able to bear the harsh conditions of the river environment because there is frequent exposure to water, sediment, and generally changing temperatures. The variable flow of the Murrumbidgee River, with the presence of debris during high-flow periods, demands that the equipment be durable.

Besides that, it should feature small size, low weight, and power consumption. The compact and lightweight device would be much easier to manipulate and deploy in an outstanding way either on the boat or attached to a buoy. Low power consumption would ensure long-time operation of the equipment without frequent replacements of batteries or access to a continuous power source.

Another factor is cost. The lower the cost, the more widely the measurement equipment can be spread around and observe the river.

In this respect, the casing of the ADCP is well done with titanium alloy. Titanium alloy has quite a few advantages. It is very resistant to corrosion, and for applications involving water bodies such as that of Murrumbidgee River, where equipment will be constantly in contact with water and possibly corrosive substances. Also, it needs to be strong and durable enough to sustain potential physical impacts and changes in pressure during and after deployment and use. Besides, titanium alloy has comparatively small density, another contribution to the general idea of keeping equipment as light as possible.

6. How to Choose the Right Equipment for Current Measurement?

While choosing appropriate equipment for measuring current in the Murrumbidgee River, a number of factors have to be considered.

Based on the Purpose of Use

The horizontal ADCP would be the proper choice if the intention is to measure the horizontal cross-section of the river current. The HADCPs are designed for accuracy in measurement of water flow in the horizontal plane, useful for understanding the overall movement of water across a particular section of the river.

For example, if the area of concern is to measure the vertical profile of the river current, one should opt for a vertical ADCP. In a vertical doppler current profiler, the velocity of the water can be measured with accuracy at each separate depth, thus providing a fine profile of how the water actually flows vertically in that river.

Based on Operating Frequency

Frequency will also be selected based on the depth of the water in the Murrumbidgee River. For depths of water up to 70 metres, an acoustic doppler velocity meter at 600 kHz is normally sufficiently adequate. The 600 kHz provides good resolution and accuracy in relatively shallower waters for measuring the water current.

Meanwhile, for deeper waters like over 70 meters and extending up to approximately 110 meters, a 300 kHz ADCP would serve better. The 300 kHz frequency can penetrate deeper into the water and still allow for reliable measurement of the water current.

There are several popular ADCP brands in the market, including 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, offering both durability and reliability. With its incredible cost - performance ratio, it provides a great alternative for measuring the water current of the Murrumbidgee 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.