National Committee on Water EngineeringPlease note that this paper is held here for archival purposes, the most up to date papers are currently held on the Engineers Australia website.
A Draft Position Paper prepared by the National Committee on Water Engineering
This draft Position Paper outlines the Australia’s water resources and how we use our water. It is increasingly being recognised that new development will not be sustainable with respect to water unless integrated strategies to manage the water cycle are implemented. This paper supports the adoption and implementation of such integrated strategies and promotes the conservation of our drinking water and the more efficient and effective re-use of our stormwater and wastewater resources to reduce the use of high quality drinkable water for purposes which only require a lower quality of water.
Continued traditional urban development in Australia's coastal cities will rapidly approach the limits of sustainability. New urban developments are increasing the pressure on the environment through the need to develop new drinkable water supplies and the discharge of polluted stormwater and treated wastewater into receiving waterways and the ocean. Unless integrated strategies to manage the total water available from all sources is adopted, new urban developments in our cities will rapidly become unsustainable.
Inland cities which are dependant on inland waterways for water supply, disposal of stormwater and wastewater, and water based recreation, are also increasingly experiencing water quality problems which to a significant degree are due to the environmental pressure exerted by expanding urban development.
The quantity of stormwater runoff from our cities is about equal to the amount of drinkable water which is supplied, so there is a potential for expanded collection, storage and re-use of stormwater for non-drinking purposes.
Similarly there is the potential to reduce the demand for drinkable water by up to 50% through the re-use of treated wastewater for non-drinking purposes.
Likewise, the abstraction of water from Australia's waterways for rural and agricultural use is increasingly impacting on the health of our river systems. In recent years there has been an increasingly recognition that our river systems require minimum (environmental) flows to maintain their health and that the needs of the environment require balancing with rural demands for water.
The sustainable development of Australia will be governed in part by our ability to better manage the water cycle and to develop new resources in an ecologically sustainable manner. Water engineers have a key role in implementing water cycle management. It involves integrating water balance, water quality and water consumption into the land use planning, design and management of both urban and rural environments.
Australia's average annual rainfall of 465 mm is considerably lower than that of other continents which range from 600 mm in Asia to 1,630 mm in South America. The estimated average annual runoff of 397 million ML is equivalent to 52 mm of runoff or just 11% of the mean annual rainfall (MAR). In contrast, the estimated runoff in Asia is 48% MAR and in South America, 57% MAR.
While these figures illustrate that Australia is relatively dry, it also suffers from high variability. For example the ratio of annual flood peak flow to annual runoff is an order of magnitude greater than ratios for the rest of the world. In hydrological terms, Australia provides the greatest challenges in responding to its extremes and variations in rainfall and runoff.
It has been estimated that Australia's annual divertible surface water resource is 100 million ML of which 21 million ML has been developed while Australia's annual divertible groundwater resource is 14 million ML of which around 2 million ML has been developed (DPIE, 1987). The divertible water resource is defined as the average annual volume of water which, using current technology, could be removed from developed or potential surface water or groundwater sources on a sustainable basis without causing adverse effects or long term depletion of storages. However, the magnitude of the divertible is not proportional to area on a State-by-State basis. The largest runoff in Australia is in the tropical regions. The runoff into the Gulf of Carpentaria and into the Timor Sea accounts for almost half of the annual runoff in Australia (Ironmonger, 1988). The regions rich in water are often remote from regions of high demand and this will determine limits on economic and sustainable growth.
It has also been estimated that irrigation of pasture, crops and horticultural irrigation represents almost 70% of Australia's total water use. Of the balance, domestic water use represents 40% of the remaining water use.
On average, major in-house uses of water comprise 55% of total domestic use. A high proportion of external use of domestic water is watering gardens. During summer months even greater amounts of water are used to water gardens, lawns and open space. This highlights the opportunity to use a lower quality of water instead of high quality drinking water for external domestic use.
The draft strategy for Ecologically sustainable Development (ESDSC, 1992) identified the goal of "ecologically sustainable development" as:
"development that improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends."
The three core objectives underpinning this goal were identified as:
It is increasingly being recognised that new development will not be sustainable with respect to water unless integrated strategies to manage the water cycle are implemented. Such strategies aim to achieve ecologically sustainable development through:
The National Water Quality Management Strategy (anzecc/awrc, 1992) identifies a similar objective, namely:
"to achieve sustainable use of the nation's water resources by protecting and enhancing their quality while maintaining economic and social development."
The goal of ecologically sustainable development will only be achieved through a re-examination of traditional practices and the formulation and implementation of new practices which:
For the first time in Australia, a national strategy for managing the quality of the country’s water resources - surface water, groundwater and coastal - is under development. The National Water Quality Management Strategy is a joint project of the Australian and New Zealand Environment and Conservation Council (ANZECC) and ARMCANZ. The NHMRC is associated with the project, having particular responsibility for areas of the strategy relating to public health.
The strategy aims to provide a comprehensive policy to achieve the sustainable use of the nation’s water resources by protecting and enhancing their quality while maintaining economic and social development. The suite of guidelines which have been released to date and of direct interest for water cycle management include:
Water cycle management can be viewed as a broadly based interactive approach that addresses competing community demands placed on a region's water resources so as to meet defined water quantity and quality objectives.
The principle infrastructure components required to satisfy water cycle management objectives include
The water cycle management scheme developed for Homebush Bay by the Olympic Coordination Authority is shown in Figure 1. It highlights the complex interactions between the four water "streams".
Figure 1 Water Cycle Management Scheme for Homebush Bay (after Moss and Listowski, 1999)
In Australia a typical household consumes an average 900 L of drinkable water per day. On average, major in-house uses represent 55% of total domestic water use. This includes toilet flushing (14%), showers (13%), laundry (12%), baths (7%), dishwashing (6%) and drinking and cooking (3%) (Ironmonger, 1988). The remaining drinkable water (45%) is applied to lawns and gardens. In the hottest months of summer, household consumption rises to around 2000 L per day. The additional demand is primarily garden watering to maintain lawns and gardens during the summer months.
The volume of drinkable water applied to household gardens and lawns is approximately equal to the entire industrial use of water. The value of water used for industry and garden and lawn watering each exceed the paid dollar value of water used for agricultural purposes even though agricultural use is some 10 times greater than industrial use and 6.5 times greater than domestic use (Ironmonger, 1988).
Better management of our drinkable water resource is integrally linked to both water conservation and the more efficient and effective re-use of our stormwater and wastewater resources to reduce the use of high quality drinkable water for purposes which only require a lower quality of water.
While modern sewage treatment plants treat our wastes to very high standards, the treated wastewater still contains nutrients and in particular biologically available phosphorus which is typically introduced in detergents. During dry years in the Murray-Darling Basin, it was concluded (GHD, 1992) that point source discharges, particularly from sewage treatment plants, are the most significant source of nutrients which can lead to algae blooms.
Modern biological treatment processes can further reduce phosphorus levels, but it is becoming more difficult and expensive to reduce phosphorus concentrations further to low levels. Even low levels may still give rise to eutrophication of the receiving waters.
The traditional approach to stormwater management has been to treat runoff as a nuisance which poses a potential risk to life and property. Nuisance flooding has been largely eliminated through the construction of piped drainage systems while larger flows up to the 100 year Average Recurrence Interval (ARI) flood are transported by trunk drains and floodways. Urban runoff has been further controlled by the construction of large detention basins to reduce downstream flow rates. The focus of control has been on the quantity of runoff.
In recent years, however there has been an increasing recognition of the need to control and improve the quality of stormwater runoff. An integrated approach to stormwater management has evolved. It can include:
Increasingly, wastewater is also being viewed as a resource which is capable of replacing drinkable water which is used for lower water quality purposes. The re-cycling of treated wastewater offers a number of advantages including (Smyth, 1992):
While it is recognised that additional costs will be incurred in providing dual use systems to reticulate treated wastewater, better sewerage system management through re-cycling has the potential to significantly reduce the requirement to treat all domestic water to drinkable quality, reduce the discharge of nutrients to receiving waters and to improve the urban environment through landscape opportunities.
Stormwater runoff from Australian cities is about equal to the amount of drinkable water which is supplied (CEPA, 1993). More than half of all domestic water is used for lower water quality purposes including garden watering and toilet flushing. There is therefore potential to also store and re-use stormwater for non-drinking purposes and to markedly reduce the demand for drinkable water. Better stormwater management will convert the liability of polluted stormwater into a valuable resource, which is capable of sustaining a range of ecosystems and water bodies of scientific, landscape and recreational value.
Water engineers have a key role in the sustainable management of the water cycle. Engineers are responsible for the identification and assessment of raw water sources; for the design, construction, operation and management of water cycle infrastructure including reservoirs, pipelines and pumping installations, water treatment plants and water supply distribution systems, sewerage systems, sewage treatment plants, drainage systems and stormwater treatment facilities including swales, gross pollutant traps, trash racks, ponds and wetlands.
The Institution of Engineers, Australia supports the adoption and implementation of integrated water cycle management strategies and promotes the conservation of our drinking water and the more efficient and effective re-use of our stormwater and wastewater resources to reduce the use of high quality drinkable water for purposes which only require a lower quality of water.
The Institution of Engineers, Australia demonstrates this support by:
Commonwealth Environment Protection Agency (1993) "Urban Stormwater, A Resource Too Valuable to Waste", Discussion Paper, February, 23 pp.
Department of Primary Industries and Energy (1987) "1985 Review of Australia's Water Resources and Water Use", Australian Water Resources Council, 2 Vols, AGPS, Canberra.
Ecologically Sustainable Development Steering Committee "Draft National Strategy for Ecologically Sustainable Development", AGPS, Canberra.
Gutteridge Haskins & Davey Pty. Ltd. (1992) "An Investigation of Nutrient Pollution in the Murry-Darling River Sytstem", prepared for the Murray-Darling Basin Commission, January, Canberra.
Hill, A.L. and Nicholson, C.J. (1989) "Water Conserving Design for Gardens and Open Space". Report No. WP89, Water Resources Directorate, Water Authority of Western Australia.
Ironmonger, D.S. (1988) "The Role of Water Resources in Australia's Economic System", Civil Engineering Tranactions, IE Aust., Vol CE30, No. 4, pp 139 - 144.
Moss, J. and Listowski, A. (1999) “Water Cycle Management at Homebush Bay”, Keynote Paper, 8th International Conference on Urban Storm Drainage, IEAust., 30 August – 3 September, Sydney.
National Committee on Water Engineering,
The Institution of Engineers, Australia
11 National Circuit, BARTON ACT 2600
Telephone: (02) 6270 6555
Facsimile: (02) 6273 1488
www:ieaust.org.au
This Position Paper was prepared on behalf of the National Committee on Water Engineering by Dr Brett C. Phillips
Last Modified:
Thursday, October 7, 2010 20:44
Comments to: peter.brady@eng.uts.edu.au