Gladstone Area Water Board supplies bulk water in two forms - raw water and drinking water. Raw water is untreated water, delivered to customers directly from Lake Awoonga. Raw water is mostly used by local industries in their processes and is unsuitable for drinking - it accounts for approximately 77% of water supplied by GAWB.
The remaining 23% of water supplied by GAWB is treated to drinking water standards and delivered to bulk drinking water customers, including the Gladstone Regional Council, who then reticulates the water to domestic customers to use in homes and commercial premises.
GAWB has a comprehensive catchment monitoring program which helps us to better understand and manage the quality of our water. This includes monitoring in the upper catchment streams which feed Lake Awoonga, within the Lake itself and downstream of the Lake Awoonga impoundment (see Source Water below).
GAWB also undertakes extensive testing throughout its treatment plants and drinking water networks to ensure that the drinking water delivered to customers is safe 100% of the time (see Drinking Water below).
Water is analysed for physical, chemical and biological parameters. Results are compared to relevant guidelines such as the;
- Australian Drinking Water Guidelines for treated drinking water;
- ANZECC guidelines for catchment waters.
Lake Awoonga is a man-made lake, designed to capture surface run-off from the many streams within the Boyne River Catchment, which feed the river and lake, providing essential water for the prosperity of the region. The Boyne River Catchment covers approximately 2, 230km2 and is bounded by the Many Peaks range to the East, the Dawes Range to the South, the Calliope Range to the South-West and the Boyne Range to the West.
Many factors influence the quality of water in Lake Awoonga, especially climate, hydrology, geology and land use. The Catchment area is located in the dry sub-tropics, with typically mild, dry winters and warm, wet summers. Approximately 57% of the Lake Awoonga catchment area is forested with remnant vegetation consistent with Brigalow Belt Bioregion Regional Ecosystems (9%) and Southeast Queensland Bioregion Regional Ecosystems (48%). Of the remainder, 2% is regrowth forest, 39% is cleared land and 2% is water storage.
Hydrologically, the Boyne system is characterised by highly variable flow and sediment regimes, as different morphological features have developed in response to topographical features and dominant flows.
The geology of the catchment consists of a range of interbedded sedimentary and volcanic formations. Limestone and mudstone are also present.
The Boyne Valley is generally zoned rural with limited commercial operations. The resident population is considered stable or falling, with a total population of around 640 people in the townships of Builyan, Many Peaks, Nagoorin and Ubobo. Landuse within the catchment remains primarily agricultural, with light to medium cattle grazing, some cropping and forestry activities. There are a number of active mineral exploration leases in the upper catchment and one operating limestone quarry.
See Catchment Management for more information.
Nutrients, such as nitrogen and phosphorus, can be a problem in Lake Awoonga because they influence the cyanobacterial (also known as Blue-Green Algae or BGA) blooms which occur naturally in the Lake during spring and summer when the temperature is higher. Some species of BGA can produce dangerous toxins which can impact animal and human health. GAWB closely monitors the BGA blooms in Lake Awoonga and if you wish to use the area for recreation you should heed the warning signs posted at the public access points. For more information see Blue-Green Algae.
The majority of water drawn from the Lake Awoonga (approximately 77%) is supplied in an untreated (raw) form to various industries in the region. Raw water is drawn from two intake and pumped into a series of 50 megalitre reservoirs using high volume pumps. Raw water is then distributed throughout the raw water network, which includes a series of reservoirs and pipelines, via gravity and booster pumps to supply industry and the drinking water treatment plants. The latest results for Raw Water Quality Data can be found here.
Untreated water from Lake Awoonga is unsuitable to drink. In order to make the water drinkable, GAWB processes raw water at its water treatment plants to meet the National Health and Medical Research Council's Australian Drinking Water Guidelines. These Guidelines represent industry best practice for drinking water quality and form the basis of Queensland's regulations regarding drinking water quality.
GAWB is committed to ensuring the highest quality of the drinking water at a cost reasonable to its customers. To do this, GAWB continuously assesses the way in which drinking water is treated, monitored and delivered to its customers. The treatment process is monitored continuously and water quality tested regularly, to ensure that 100% of drinking water meets GAWBs Drinking Water Quality Management Plan, regulatory requirements and Australian Drinking Water Guidelines.
The Water Treatment Process
- Coagulation - a chemical coagulant called aluminium sulphate (alum) and a polyelectrolyte coagulant aid is mixed into the water. The alum forms into tiny, sticky particles that attract dirt and contaminants in the water.
- Flocculation - the alum and dirt particles are slowly mixed to grow into larger particles known as ‘floc'.
- Clarification - the water then flows to larger clarification tanks where the floc either sink or are floated using tiny air bubbles, removing most of the particles from the water column.
- Filtration – clarified water flows through filters made of anthracite, sand, and gravel to filter and trap tiny bits of dirt still in the water.
- pH correction – the pH of the water is adjusted for optimal disinfection and to protect pipelines and infrastructure from corrosion.
- Disinfection - chlorine is then mixed with the water to kill any pathogens.
The water treatment process is continuously monitored by the water treatment plant operators and via online instrumentation to ensure it meets drinking water specifications 100% of the time. Once the water has been treated it is pumped to nearby reservoirs and fed via gravity and booster pumps through pipelines to customers. The treated water supplied in the region is generally classed as "moderately hard".