Improving the sustainability and cost effectiveness of urban water supplies
By Dr. Evan Thomas, Senior Soil Scientist
With Australia's population projected to increase by between 62% and 113% by 2061, and climate extremes being experienced countrywide, it has never been more important than now to re-evaluate approaches to cost effective and sustainable urban water supply management.
The Challenge: South East Queensland's urban water supply
Urban water supply systems consist primarily of large catchments, reservoirs, and water treatment and conveyance systems. In some instances, for example Brisbane, water is conveyed from the reservoir to the main water treatment facility via a natural river channel. Where this occurs, the quality at the inlet to the treatment plant is affected by the activities along the main conveyance channel as well as all of the tributary waterways. In the case of Brisbane, this includes the Lockyer-Bremer river system as well as the Brisbane River itself.
Activities and management within these catchments affect the water quality at the treatment plant and the cost to effectively treat it. In some cases, the sediments in the water may clog the inlets to the treatment plant as happened during the 2011 floods in South East Queensland when a significant part of the water supply to Brisbane was almost shut down due to excessive sediment at the Mt Crosby treatment plant.
The costs associated with managing these risks, through engineering solutions alone, can run into billions of dollars. It may be more cost effective and sustainable to use an ecological engineering approach. This was demonstrated in the well-known case of the New York City water supply system where a new water filtration facility was estimated to cost US$6-8billion. However, the cost of protecting and restoring the natural ecosystem processes to achieve the same outcome was approximately US$1.3 billion (see sidebar).
The Solution: An Ecological Engineering approach to Catchment Management
For South East Queensland (SEQ) three issues emerge with respect to the ecological catchment management of water supplies:
- Quantity of water supply;
- Frequency of water supply;
- Water quality.
These factors are driven by the reasonable need to have surety of supply, in terms of both quality and quantity, for both community and industrial needs during times of drought and; for the protection of property during times of flood. However, the role of the ecosystem in the provision of these services has generally been given only limited consideration.
Catchments are currently defined by spatial extent and managed by broad scale factors relating to infiltration, drainage and surface runoff. The role that land use and land management play within the catchment are not well considered and yet, from the example in New York City, could result in greatly reduced costs to deliver an equivalent or better and more reliable service.
Riparian restoration, erosion mitigation and overall catchment management can significantly filter and remove sediment and nutrients from run-off and reduce erosion of stream banks, improving stream water quality, aquatic ecological health, and the quality of water entering dam storages. This in turn can significantly reduce the cost of process treatment.
Elements of Ecological Engineering approach to Catchment Management include:
- Understanding catchment soil and land resources;
- Understanding catchment land uses and management;
- Understanding catchment hydrology;
- Stakeholder engagement, education and involvement;
- Adaptive management guided by science including projects to improve grazing, reduce erosion, repair waterways, manage pests and weeds and restore degraded habitats;
- Working with stakeholders in the progressive adoption of best management practices including:
- Responding to the issue of water salinity by making better use of salt affected lands by identifying and planting salt tolerant species; and
- Maintaining native deep-rooted vegetation and ensuring a good level of groundcover.
The Benefits of an Ecological Engineering approach:
In addition to direct drinking water quality benefits, catchment based approaches to water quality and quantity management provide numerous co-benefits. These can include enhanced biodiversity from riparian revegetation works, carbon sequestration in tree plantings, improved conditions for aquatic wildlife, as well as reduced soil and nutrient loss from farming operations, and improved agricultural productivity from farming practices that favour rainfall infiltration and soil conservation. These practices are particularly important in “open catchments” such as Brisbane’s, where the catchment area for water harvesting is shared with numerous other land uses.
The application of catchment management models, land resource survey and interpretation, and adaptive management techniques combined with community and stakeholder engagement can result in changes to land use and management within the catchment that target “hot spots” and “hot issues”. This can result in highly cost-effective improvements to the quality of water and reliability of supply.
Essentially, Ecological Engineering means that solutions to environmental problems can actually be opportunities and they certainly don't need to be a decision between the environment or finances. Ecological Engineering presents solutions to issues of human impact in a growing world in a way that can reduce risk, reduce cost and add value for organisations, the community and the environment. For further details of Verterra's water and municipal environmental and resource capabilites that deliver on the triple bottom line of economic, environmental and community benefits, click here.
Case Studies in Ecological Catchment Management
Australian Bureau of Statistics (2013). 3222.0 - Population Projections, Australia, 2012 (base) to 2101.
Everhard, M. (2009). The Business of Biodiversity, 107-108.
Ashendorff, A., Principe, M.A., Seely, A., LaDuca, J., Beckhardt, L., Faber, W. & Mantus, J. (1998). Watershed protection for New York City's supply. Journal of American Water Works Association, 89, 75–88.
Chichilnisky, G. & Heal, G. (1998). Economic returns from the biosphere. Nature, 391, 629–630.
SEQ Catchments, Water Quality Offsets Position Paper