Restoring Moreton Bay to Health Using TWCM
At more than 3.1 million people, and expected to rise to around 4.4 million by 2026, Southeast Queensland (SEQ) has one of the fastest growing populations in Australia. Projected population expansion will further pressure the region’s waterways, which largely drain into Moreton Bay and are already in poor health, as are areas of the Bay itself.
In 2009, when the Ecosystem Health Monitoring Program (EHMP) reported a general decline in all receiving estuaries and waters in SEQ, Moreton Bay was found to have declined from a B to a D, the lowest ecosystem health rating in more than a decade of monitoring.
The 2011 Report Card Results were more positive, with some freshwater streams and estuaries improving in grade. This was despite the fact that the flooding events which hit South East Queensland in January had moved a significant amount of sediment and nutrients from the catchments out into the bay. Even so, the flooding events highlighted the need to prepare catchments for rainfall events by managing erosion, rehabilitating riparian (riverbank) areas, stabilising creek channels, investing in good agricultural practices and sustainably managing urban water.
Achieving this requires detailed water resource management plans that ensure land use and infrastructure planning is environmentally sustainable, and securing reliable water supplies to cater for forecast population growth.
Indeed such planning is as necessary as it is desirable: the Queensland Government, under its revised Environmental Protection (Water) Policy 2009 (EPP Water), now requires all Local Government Authorities (LGAs) with a population of more than 25,000 people to develop and implement a Total Water Cycle Management (TWCM) Plan specific to its local government area before 1st July 2014. In SEQ, local governments must develop their plan before 1st July 2012. The plan must identify the interrelationships between all elements of the water cycle, to facilitate sustainable development and planning.
It must provide for stormwater management to improve quality and flow; management of flood risk, and integration of water use in the local government area. It also must give consideration to demand management; water recycling and ways to use recycled water; stormwater harvesting and forecast of water supply requirements for the area.
In response to its pressing water issues, Moreton Bay Regional Council (MBRC) has become the first LGA to make significant progress with TWCM Planning. By identifying the unique challenges of the region through the TWCM Plan, the Council hopes to ensure the existing social, environmental and economic values of the region are maintained or enhanced
To that end, engineering and environmental consultancy BMT WBM, using a suite of modelling tools from eWater including Source for catchments, Urban Developer and music, has worked in partnership with MBRC to develop a TWCM Strategy for the region as a first phase of the overall TWCM Plan. BMT WBM will shortly deliver a final TWCM Plan for the region.
Work to date so impressed the judges that it won the Excellence in Strategic or Master Planning award in the recent 2011 SIAQ Awards for Excellence. The Award recognises excellence in development of integrated stormwater management plans. Projects are expected to demonstrate superior standards in the application of best planning practices for stormwater and integrate stormwater within broader considerations such as land use planning, Integrated Water Cycle Management, sustainability and liveability to ensure multiple benefits are achieved through meaningful collaboration with stakeholders.
“Most of the time what it showed us was that we couldn’t achieve the predicted sustainable loads even if the catchments were fully naturalised. And it gave us a very quick assessment to be able to understand that perhaps the water quality targets that had been set for deriving the sustainable loads were not appropriate for those catchments and needed to be revised.
“Without Source we could not have been able to so clearly understand the influence of the land on the receiving environment.”
To assist in the selection of solutions for further investigations during the detailed planning stage, a Multi Criteria Analysis (MCA) assessment approach was used.
Objectives for the TWCM Strategy were set to reflect triple bottom line (environmental, social and economic) performance targets of the region, as well as meeting legislative and policy requirements.
Criteria with which to assess the performance of each solution in meeting these overarching objectives were then developed.
Urban Developer: Understanding development pressures
In the second phase BMT WBM used Urban Developer to examine the pressures coming from areas of new development within the region, and to highlight their impact upon water supply and the likely degree of wastewater production.
Urban Developer allows urban water managers to compare integrated water management options, ranging in scale from the allotment to the cluster level.
This next generation software tool from eWater challenges the conventional silo approach to modelling the different streams of the urban water cycle of stormwater, waste water, water supply and re-use options.
“Looking at the areas of new development within the region, we were able to use Urban Developer to examine alternate supply options relatively quickly: the rainwater tanks, stormwater harvesting, recycled water. We could see what each of those elements delivered individually, and determine the best combination of those to meet our objectives for an area,” says project manager and senior environmental engineer at BMT WBM, Nicole Ramilo.
“The outcomes from that work identified relatively quickly that we could meet a lot of the yield using rainwater tanks, if required. We could also reduce pollutant loads significantly if we could use recycled water quite a bit in a catchment. What we wanted to do was take treated wastewater, and use it in park areas as well as for outdoor watering and other suitable uses in the residential areas.
“That led to an understanding of the relative merits of combinations of different sources and which ones were best able to help us.
“The issue then became: how do we take that data further forward, and that was through using the hard numbers in another round of Multi Criteria Analysis.”
MUSIC: examining scenarios
MUSIC – model for urban stormwater improvement conceptualisation – is designed to help urban stormwater professionals visualise possible strategies to tackle urban stormwater hydrology and pollution impacts.
For the MBRC work BMT WBM used MUSIC to assess the performance of the treatment options and retrofitting for new developments.
“What we were looking at there in terms of new developments was the implications of addressing state legislative requirements and local government planning policy,” Ramilo says. “Then we took it a step further by asking what would be required to achieve no change in loads from new development.
“We used MUSIC to game out those scenarios to determine what the area required and therefore what the ‘land take’ would be, the likely cost of those solutions, and then how effective they were on a unit cost basis and on a dollars per kilo removed basis.”
The ultimate goal of the exercise, Ramilo says, is to tie costing information to the pollutant load and flow information, and then to develop “cost curves” with the assistance of CSIRO to help Council evaluate treatment options.
“Being able to have a powerful suite of tools to call on has been a big advantage,” Ramilo says. “It was about having the right tools at the right scale that really helped us bring all of that together in an integrated fashion.
“What it will allow us to present is options for implementation for Total Water Cycle Management including those which will give the best cost effectiveness, in terms of a triple bottom line assessment: social, economic and environmental.”
Image courtesy Moreton Bay Regional Council
Source for catchments: Accounting for water cycles
The Moreton Bay Council region comprises 14 major catchments extending from the hinterland to the coast and covering an area of approximately 200,000 hectares. Bordered by the local government areas of Brisbane to the south, Sunshine Coast to the north, and Somerset to the west, the region includes the townships of Samford, Dayboro, Strathpine, Petrie, North Lakes, Caboolture, Woodford, Mt Mee, Bribie Island, Deception Bay and the Redcliffe Peninsula.
Developing a TWCM plan for the region entailed understanding both current and likely future conditions affecting each catchment. To achieve this, BMT WBM developed water cycle ‘accounts’ outlining the existing (2010) and future (2031) conditions for all elements of the water cycle in every catchment. Those elements were: rainfall, evapotranspiration, groundwater drainage loss, rural extractions, reticulate water yield, reticulated water demand, imported/exported reticulated water, network leakage, stormwater discharges, wastewater discharges and recycled water.
The accounts were informed by information gathered during an initial data collection and review process. Assumptions used to quantify key elements of the water cycle were clearly reported to ensure transparency and identify any limitations to the study.
Here Source for catchments played a critical role. Source enables local knowledge, data and models to be combined with industry best practice to generate effective, transparent catchment management scenarios and options. The software provides a framework for modelling the amounts of water and contaminants flowing though a catchment and into major rivers, wetlands, lakes, or estuaries. Source integrates an array of models, data and knowledge that can be used to simulate how climate and catchment variables (rainfall, evaporation, land use, vegetation) affect runoff, sediment and contaminants. The output can be used to offer clear scenarios and options for making improvements in a catchment.
“We used eWater’s Source for catchments in that first phase to model the constituents and the hydrology of the land, and put that together with the built infrastructure sources and other factors,” says BMT WBM National Practice Leader, Water Quality Tony Weber. “What Source for catchments gave us was the land surface source and sinks in terms of flows and in terms of water quantity and water quality, which we then combined with water supply and wastewater supply demands, waste water production, and so on.
“Then in phase two we used Source in a similar role, but also to provide forcing data for receiving water quality models. This helped us determine the sustainable loads into the various catchments within the Moreton Bay region,” he says.