Water Services is a business unit of Power and Water Corporation that provides water and wastewater services to 19 major and minor urban centres across the Northern Territory.
The primary water source for centres across the Northern Territory is groundwater. Exceptions are Darwin, Katherine and Pine Creek, which also access surface water sources. Most of Darwin's water supply comes from Darwin River Dam. To ensure ongoing water quality, no development or uncontrolled public access is permitted within the catchment.
The protection of potable public water sources is a core responsibility of Power and Water. These water sources include borefields and their recharge zones and surface water supply reservoirs and their catchments. We are committed to proactive management and protection of drinking water sources and providing high quality drinking water to the public throughout the Northern Territory.
Protection of water quality is paramount. We also strive to protect other benefits provided by water sources and their catchments, including environmental, cultural heritage, public recreation and amenity values to the extent they do not compromise drinking water quality and the operational requirements of water supply. These actions protect the natural purification processes and reduce the risk of contamination of raw water sources.
Power and Water actively manages activities that have the potential to compromise water quality or the environment, operation of water source infrastructure, or other important values and benefits of drinking water sources. The Catchment and Water Source Protection Strategy and Policy documents focus on these values.
Power and Water currently manages two large surface water sources (reservoirs and their catchments), Darwin River Dam and the smaller Copperfield Reservoir at Pine Creek. Surface water is also drawn from the Donkey Camp weir on the Katherine River and this forms the major component of Katherine's public water supply.
The Darwin Region Water Supply Strategy identifies a number of potential future surface water source options including Manton Reservoir and several possible alternative large water storages.
Nearly all of the 19 locations currently serviced by Water Services are in part (and often completely) reliant upon groundwater for their drinking water supply. Communities are supplied with water from a number of bores that draw water from subsurface aquifers at a range of depths and in a variety of geological environments.
Some drinking water sources are better protected than others, such as those with 'closed' catchments. Darwin River Dam is an example. However, well protected water sources are still vulnerable to a broad range of potential risks and threats.
Summary of water sources
Darwin River Reservoir
Howard East Borefield
Donkey Camp Weir
Roe Creek Borefield
Power and Water is committed to effective management of drinking water supplies and providing high quality and safe drinking water to consumers. The process to achieve this is outlined in the Drinking Water Quality Policy Statement and Customer Contract. While Power and Water has a primary responsibility for providing safe drinking water through the Water Supply and Sewerage Services Act 2000 (NT) several government agencies are involved in the delivery of safe drinking water.
Sophisticated monitoring and treatment processes ensure that the drinking water meets very high standards. More information is available in the current Drinking Water Quality Report.
The Australian Drinking Water Guidelines (ADWG) is the primary reference on drinking water quality used by Power and Water and the Department of Health. The ADWG recognises that "prevention of contamination provides greater security than removal of contaminants by treatment, so the most effective barrier is protection of source water to the maximum degree practical".
The Department of Health has detailed information about harmful organisms in water and public health concerns.
Water treatment process
Treating water protects our health by ensuring safe drinking water is provided to our customers.
The process and technologies used to remove contaminants from water and to improve and protect water quality are similar around the world. The choice of treatment used depends on characteristics of the water, types of water quality problems likely to be present and the costs associated with the different treatments.
Most of our drinking water needs very little treatment as it comes from protected catchments that supply high quality water. Water is disinfected as it leaves the storage reservoirs and enters the supply system.
Some of our water comes from unprotected catchments and is fully treated at water treatment plants. This process includes steps to remove impurities before the water is disinfected and is similar to common water treatment processes used throughout the world.
The most widely applied water treatment technology is a combination of some or all of coagulation/flocculation, clarification, filtration and disinfection:
Chemical, usually liquid aluminium sulphate (alum), is added to help bacteria and small solid particles stick together, forming larger particles that then settle in-situ and can be easily removed.
Mechanical settling basins called clarifiers, use gravity to separate solid particles and remove colour.
Particles are removed as water passes through filters or membranes. The method varies between treatment plants:
- Gravity media filtration uses filters containing layers of sand
- Membrane filtration uses semi-permeable membranes with billions of microscopic pores
Chlorine, chloramine (chlorine and ammonia) or ultraviolet light are used to destroy disease-causing bacteria. Chlorine provides continual and effective protection from the treatment plant to the tap and is especially effective where long pipelines are used and high water temperatures can increase the potential for growth of harmful organisms in the water. Chlorine is used for disinfection purposes in all drinking water supply systems.The amount of chlorine added is relative to the purity of the water and is typically less than one milligram per litre.
Fluoride is found naturally in our water or is added in small amounts, less than one milligram per litre, to help prevent tooth decay. Providing water that contains fluoride is a legal requirement administered by the Department of Health.
- pH correction
Lime, caustic soda or soda ash is added to neutralise the pH of water as chlorine and fluoride are slightly acidic. The minerals in lime also help prevent household pipes and fittings from corroding.
Water treatment plants
Power and Water operates two major water treatment plants at Katherine and Yulara. The other water plants consist either of a disinfection and/or fluoridation process.
Summary of treatment plants and processes
Darwin Water Story
The Darwin Water Story provides information about the current water supply and sets out a discussion on future challenges and possible solutions.