Why Do We Measure Albury's River Flows?

1. Where is Albury?

Geographical Background

Albury is a small city on the Murray River, which marks the border between New South Wales and Victoria in south-eastern Australia. It is situated some 550 kilometers southwest of Sydney and 320 kilometers northeast of Melbourne and is located on the northern edge of the Murray Valley plain. It is bordered by rolling hills in the north and the wide flood plains of the Murray River in the south, with the Great Dividing Range in the background. At an altitude of approximately 164 meters above sea level, it provides the area with its four-season temperate climate.

The Human/Cultural

Founded in the 1830s as a river port, Albury has grown into a city of more than 50,000 population. It is famously known for its rich Indigenous history, with Wiradjuri nation who have occupied the area for tens of thousands of years. Its colonial history as a city is also linked with the Murray River that facilitated trade and settlement during colonial times. Albury of today is a booming cultural hub with its Albury Wodonga Eisteddfod and its historic features such as the Albury Botanic Gardens and the Regent Cinema, an Art Deco cinema. It has a twin city relationship with Wodonga in Victoria, and as a cross-border community, they have shared amenities and economic interests.

Hydrology and River Overview

The principal river system influencing Albury is the Murray River. The Murray flows west from its source in the Snowy Mountains of New South Wales for 2,508 kilometers, the longest river in Australia, to discharge into the Southern Ocean at Adelaide. The river is joined at Albury by its principal tributary, the Murrumbidgee River, upstream near Narrandera.

The Murray River is at the heart of Albury's survival and prosperity. It provides 90% of the city's drinking water, irrigates large areas of agricultural land (such as the region's citrus orchards and wineries), and serves as a significant transport route for water sports and commercial vessels. Ecologically, the river and related wetlands provide habitat for endemic aquatic species like the Murray cod, the platypus, and the river red gum that are dependent on natural regimes of flow.

Along Albury, the Murray River widens to an average 80-100 meter width, with depths ranging from 3 to 10 meters. The floodplain of the river, several kilometers inland from the shores, is occasionally inundated, fertilizing the soil and supporting dense habitats. Tributaries like the Kiewa River (draining Victoria) feed into the Murray upstream of Albury, contributing significantly to its water volume. The water supply of the city is directly linked with the river, where water for treatment and supply is drawn by pumping stations and treated sewage water is redirected to the river after being treated.

2. What is the Situation of River Flow around Albury?

Influencing Factors

Precipitation and Runoff

Albury receives an average rainfall of 690 millimeters annually, of which the majority of it falls during the period from September to November. Summer rains are normally identified with thunderstorms generating rapid runoff into the Murray River. Snowmelt from springs in the Snowy Mountains has a significant impact on river flow, adding to volumes during October and December. Winter months tend to have lower flows, and there is occasionally a period of drought reducing levels even more. Catchment runoff, which includes indigenous forest and agricultural land, impacts the quality and quantity of water with seasonally fluctuating loads of sediment and nutrients.

Morphology and Topography of the River

Murray River at Albury flows in a relatively broad valley with a shallow gradient, thus producing moderate current velocities of 0.3-0.8 meters per second under normal conditions. The river bed is gravel and sand, with fish habitat provided by submerged logs and rock. Meanders are typical, and the river course shifts gradually over time, especially during floods. The flat topography of the floodplain makes it possible for high flows to spread over large areas and have at some locations water depths of several meters. The presence of levees across some areas of Albury modifies the natural regimes of flow, protecting urbanized regions but modifying the ecological floodplain processes.

Reservoir Operation

There are several reservoirs upstream that regulate the flow of the Murray River in the Albury area, with the largest being Lake Hume, 15 kilometers upstream. Lake Hume, constructed in 1936 at a capacity of 3,038 gigaliters, regulates downstream flows for flood control and supply of irrigation water and for city use. Dry season minimum flows are maintained by releases from Lake Hume, and excess water is stored during wet seasons to prevent flooding. Flow regimes are also affected by the operation of the Snowy Mountains Scheme, a series of dams and hydroelectric power plants, with water taken off for power production and subsequently being discharged back into the river system.

Historical Hydrological Events

1956 Floods

One of the most severe floods in Albury's history occurred in 1956, when heavy rain and snowmelt caused the Murray River to flood to a height of 12.3 meters in Albury. The flood covered a large part of the central business district and suburbs of the city, displacing thousands of residents from their homes. Agricultural land was affected, causing widespread loss of crops, and such infrastructure as roads and bridges was extensively damaged. (Source: Albury City Council Archives, 1956 Flood Report)

2007-2009 Drought

The Millennium Drought, peaking between 2007-2009, led to record-low flows in the Murray River. Lake Hume fell to just 18% capacity, and water restrictions affected Albury for several years. Low flows generated high salinity in the river, affecting drinking water treatment and harming aquatic environments. Bank erosion was exacerbated as vegetation killed off, and recreational activities like boating were severely limited. (Source: Murray-Darling Basin Authority Annual Report, 2009)

Monitoring of these events is essential to develop effective flood reduction strategies, drought water supply planning, and maintain river environmental health in the context of climate variability.

3. How to Monitor River Flows in Albury?

Conventional Methods

Surface Drift Buoy Method

This method involves releasing floating buoys, usually foam, into the Murray River and tracking their movement by visual means or GPS. Surface velocity is computed from measurements of the time taken to travel a known distance. Although cheap and simple, it will provide readings only for the surface layer of water and also gets affected by wind and currents, leading to inaccuracies. Due to these, it is not widely used for official records in Albury.

Anchored Boat Technique

By suspending a current meter from an anchored boat, researchers measure water velocity at various depths. The meter, a rotating propeller on a counter, records the number of rotations over a set period to calculate speed. The method provides vertical profiles of flow but is time-consuming, with multiple measurements requiring coverage across the river width. It is also labor-intensive and risky during high flow, making it not feasible to employ for routine monitoring.

ADCP Introduction

Acoustic Doppler Current Profilers (ADCPs) are the industry standard in the measurement of Albury river flows. ADCPs use sound waves to measure water velocity at hundreds of points in the water column, from the surface to the river bed, simultaneously. ADCPs are deployed from boats or fixed structures and emit acoustic pulses that bounce back from suspended particles in the water. By quantifying the frequency shift of the reflected pulses, they generate high-resolution flow profiles in real time. It is faster, more accurate, and safer than traditional methods, allowing for widespread measurements even under adverse conditions.

4. How Does ADCP Work Based on the Doppler Principle?

ADCPs operate based on the Doppler principle, where sound waves experience a frequency change when reflected from moving targets. The device emits acoustic pulses at frequencies typically between 300 kHz and 1200 kHz from multiple transducers. As the pulses hit particles in the water, the frequency shifts proportionally to the velocity (and thus the velocity of the water) of the particles. The ADCP records velocity vectors at different depths by comparing the emitted and received frequency. These are combined with the river's cross-sectional area to measure discharge (volume of water flowing past a point), a highly significant parameter for water management.

5. What is Required for the High-Quality Albury River Flows Measurement?

Equipment Requirements

• Material Reliability: ADCPs used in the Murray River must withstand long-term water exposure, with intermittent high sediment loads. Stainless steel or titanium materials resist corrosion, offering long-term service.
• Portable Design: 5-10 kilogram portable ADCPs are a necessity for Albury's riverine environment operation, with simplicity of deployment from small boats or riverbanks.
• Affordability: With frequent monitoring being essential, equipment must be value for money, with little maintenance costs and long-life batteries capable of operating for weeks or months without replacement.

6. How to Choose the Suitable Current Measuring Equipment?

Deployment Method

• Ship-Borne (Moving Boat) ADCP: Used by organizations like the Murray-Darling Basin Authority for monthly flow surveys, this setup quite effectively spans the river width, providing data on discharge and flow regimes along Albury's reach of the Murray.
• Bottom-Mounted (Fixed) ADCP: Bottom-mounted fixed ADCPs, placed at strategic locations such as the Albury Weir, provide continuous data on flow variations, including response to reservoir releases and storm events, in support of flood warning systems.
• Cableway ADCP: Used at some sites where there is existing infrastructure, such as the Hume Dam spillway, to safely record flows during periods of high water without requiring a boat.

Working Frequency

• 600 kHz ADCPs: Best suited to the depth of the Murray River near Albury (3-10 meters), with high resolution to detect changes in flow near the riverbed and near structures such as bridges.
• 300 kHz ADCPs: Used in the deeper areas upstream, e.g., close to Lake Hume, where additional range is needed to get full water column velocities.

Brand Recommendations

Few of the world ADCP big brands include Teledyne RDI, Nortek, and SonTek, which offer high-quality and reliable products used in various hydrological study and monitoring programs. As a budget - friendly option, the ADCP manufacturer Chinese company’s "China Sonar Panda ADCP" comes highly recommended. Made of all - titanium alloy, it is more strengthful and reliable and is a suitable option to endure the nasty river condition surrounding Thrissur. As an "affordable ADCP", it boasts decent quality performance at budget price. For more information, visit https://china-sonar.com/.

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