Exploring a flow regime and its historical changes downstream of an urbanised catchment
- Ebbs, David, Dahlhaus, Peter, Barton, Andrew, Kandra, Harpreet
- Authors: Ebbs, David , Dahlhaus, Peter , Barton, Andrew , Kandra, Harpreet
- Date: 2018
- Type: Text , Conference paper
- Relation: 10th International Conference on Water Sensitive Urban Design: Creating water sensitive communities (WSUD 2018 & Hydropolis 2018), Perth, Western Australia p. 131-141
- Full Text:
- Reviewed:
- Description: The rapid growth of Ballarat's urban area, an inland city of approximately 100,000 people in south-eastern Australia, suggests that it is suitable for stormwater capture and reuse. With a threefold increase in the number of dwellings in recent decades, along with a 90% increase in their average size, it should follow that there is evidence of more flow being generated from the urban areas. However, while additional runoff from the growth of impervious areas may be occurring, the overall flow in the receiving river has dramatically reduced with a 60% decrease in the rainfall-runoff relationship since 1997. This reduction in river flow seems disproportionate to any association with the Millennium Drought which occurred during 1997 to 2009. The evidence of river flow has been complicated by other changes in the catchment. A change in the rainfall-runoff relationship has been identified in other similar catchments, and may lead to significant impacts on water resource management over the long term. To better understand the impacts on river flow downstream of an urbanised catchment, the flow has been partitioned into various components over time using the daily stream flow data available from 1957. Base flow, calculated as the stream flow after periods of four or more days without rain, has decreased. Transfers, predominantly from other catchments for use as potable supply and entering the river via the waste water treatment plant, have remained steady, but now make up the vast majority of dry weather flow. While climatic variations have impacted the river significantly the actual streamflow reduction has been twice that predicted by data from the Australian Water Resources Assessment. A significant increase in the number of small farm dams due to the expansion of peri-urban living around Ballarat explains a further portion of the flow reduction. This paper highlights multiple factors which influence river flow and demonstrates how increases in urbanised area do not necessarily create additional river flow at larger aggregate scales. The investigation therefore provides a cautionary tale around assumptions of stormwater harvesting and any perceived benefit to river flow, and provides insights into the importance of collecting water information of the correct type and scale to help inform future integrated urban water management efforts.
- Authors: Ebbs, David , Dahlhaus, Peter , Barton, Andrew , Kandra, Harpreet
- Date: 2018
- Type: Text , Conference paper
- Relation: 10th International Conference on Water Sensitive Urban Design: Creating water sensitive communities (WSUD 2018 & Hydropolis 2018), Perth, Western Australia p. 131-141
- Full Text:
- Reviewed:
- Description: The rapid growth of Ballarat's urban area, an inland city of approximately 100,000 people in south-eastern Australia, suggests that it is suitable for stormwater capture and reuse. With a threefold increase in the number of dwellings in recent decades, along with a 90% increase in their average size, it should follow that there is evidence of more flow being generated from the urban areas. However, while additional runoff from the growth of impervious areas may be occurring, the overall flow in the receiving river has dramatically reduced with a 60% decrease in the rainfall-runoff relationship since 1997. This reduction in river flow seems disproportionate to any association with the Millennium Drought which occurred during 1997 to 2009. The evidence of river flow has been complicated by other changes in the catchment. A change in the rainfall-runoff relationship has been identified in other similar catchments, and may lead to significant impacts on water resource management over the long term. To better understand the impacts on river flow downstream of an urbanised catchment, the flow has been partitioned into various components over time using the daily stream flow data available from 1957. Base flow, calculated as the stream flow after periods of four or more days without rain, has decreased. Transfers, predominantly from other catchments for use as potable supply and entering the river via the waste water treatment plant, have remained steady, but now make up the vast majority of dry weather flow. While climatic variations have impacted the river significantly the actual streamflow reduction has been twice that predicted by data from the Australian Water Resources Assessment. A significant increase in the number of small farm dams due to the expansion of peri-urban living around Ballarat explains a further portion of the flow reduction. This paper highlights multiple factors which influence river flow and demonstrates how increases in urbanised area do not necessarily create additional river flow at larger aggregate scales. The investigation therefore provides a cautionary tale around assumptions of stormwater harvesting and any perceived benefit to river flow, and provides insights into the importance of collecting water information of the correct type and scale to help inform future integrated urban water management efforts.
- Ebbs, David, Dahlhaus, Peter, Barton, Andrew, Kandra, Harpreet
- Authors: Ebbs, David , Dahlhaus, Peter , Barton, Andrew , Kandra, Harpreet
- Date: 2018
- Type: Text , Journal article
- Relation: Water Policy Vol. 20, no. 3 (2018), p. 617-630
- Full Text: false
- Reviewed:
- Description: Forecasting supply and demand is fundamental to the sustainability of the water system. Demand for urban water seems on an ever-upward trajectory, with use increasing twice as quickly as population throughout the 20th century. However, data from Ballarat, a city in south-eastern Australia, show that despite this conventionally held wisdom, total water usage actually peaked over 30 years ago. While the 1997–2009 ‘Millennium Drought’ had some effect, the decline commenced many years before. Initially, this was due to a reduction in external domestic water use, which correlates well with an increase in water price. However, the effect was found to not be purely economic as the price was not volumetric-based. Internal water use seems more affected by technological advances and regulatory controls. Interestingly, there was no relationship found between rainfall and water demand. The role of price, water-reduction education programmes, water-efficient technology and regulation supports previous research that a multifaceted approach is required when developing demand-reduction policies and strategies. This finding emphasises the importance of understanding the component of consumptive behaviour being targeted, and ensuring that policies being implemented are appropriate for the desired behavioural change.
Harvesting stormwater : Testing the paradigm by assessing the impacts with an inter-disciplinary case study
- Authors: Ebbs, David
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Integrated Urban Water Management (IUWM) is often proposed as a framework for comprehensively managing the water cycle in urban areas. One of the tenets of IUWM is that, due to increased impervious area, stormwater runoff in excess of the natural flow could be captured and used to supplement the water supply, while mitigating the environmental impact. This thesis tests that theory through an inter-disciplinary case study utilising legacy data for the regional city of Ballarat, Australia. The case study approach has enabled the water balance of an urbanised catchment to be better understood in various ways and provided for five tightly nested research projects, being: 1. Does the long-term development of water management within a city provide insight into what drives decisions, therefore informing future progress? 2. Can the drivers of water use be adequately determined from a community wide, historical analysis such that future regulatory decisions can be informed? 3. Will assessment of the long-term streamflow of a river, combined with an urban water balance of the catchment, enable the identification of additional stormwater flow due to urbanisation, in excess of the natural flow? 4. Can the impact of urbanisation on groundwater be identified (i.e. trends quantified or qualified) from the city’s legacy data or any available data sources, or models? 5. Is it possible to establish a comparative analysis technique that accounts for the uncertainty of information which changes over time, maintains intellectual rigour and is understandable and easily presented? IUWM was found, perhaps unsurprisingly, to be a complex problem with the challenges being very contextual on the particular catchment and city being studied. This research revealed that evidence of greater volumes of water being generated from increasingly urbanised impervious catchments is not easy to find. This finding may challenge conventional thinking and means that decisions on stormwater harvesting and WSUD practices more broadly should first be informed by evidence of the water balance. This research also revealed some very significant challenges in the water industry with finding and effectively using very dispersed data sets which are held and managed across multiple water agencies in various digital and hard copy formats. Information and data availability is critical to all aspects of IUWM, including in the measurement of its success, and so this research reminds the water industry of the importance of its data management practices.
- Description: Doctor of Philosophy
- Authors: Ebbs, David
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Integrated Urban Water Management (IUWM) is often proposed as a framework for comprehensively managing the water cycle in urban areas. One of the tenets of IUWM is that, due to increased impervious area, stormwater runoff in excess of the natural flow could be captured and used to supplement the water supply, while mitigating the environmental impact. This thesis tests that theory through an inter-disciplinary case study utilising legacy data for the regional city of Ballarat, Australia. The case study approach has enabled the water balance of an urbanised catchment to be better understood in various ways and provided for five tightly nested research projects, being: 1. Does the long-term development of water management within a city provide insight into what drives decisions, therefore informing future progress? 2. Can the drivers of water use be adequately determined from a community wide, historical analysis such that future regulatory decisions can be informed? 3. Will assessment of the long-term streamflow of a river, combined with an urban water balance of the catchment, enable the identification of additional stormwater flow due to urbanisation, in excess of the natural flow? 4. Can the impact of urbanisation on groundwater be identified (i.e. trends quantified or qualified) from the city’s legacy data or any available data sources, or models? 5. Is it possible to establish a comparative analysis technique that accounts for the uncertainty of information which changes over time, maintains intellectual rigour and is understandable and easily presented? IUWM was found, perhaps unsurprisingly, to be a complex problem with the challenges being very contextual on the particular catchment and city being studied. This research revealed that evidence of greater volumes of water being generated from increasingly urbanised impervious catchments is not easy to find. This finding may challenge conventional thinking and means that decisions on stormwater harvesting and WSUD practices more broadly should first be informed by evidence of the water balance. This research also revealed some very significant challenges in the water industry with finding and effectively using very dispersed data sets which are held and managed across multiple water agencies in various digital and hard copy formats. Information and data availability is critical to all aspects of IUWM, including in the measurement of its success, and so this research reminds the water industry of the importance of its data management practices.
- Description: Doctor of Philosophy
Losing stormwater: 60 years of urbanisation and reduced downstream flow
- Ebbs, David, Dahlhaus, Peter, Barton, Andrew, Kandra, Harpreet
- Authors: Ebbs, David , Dahlhaus, Peter , Barton, Andrew , Kandra, Harpreet
- Date: 2018
- Type: Text , Conference paper
- Relation: 10th International Conference on Water Sensitive Urban Design: Creating water sensitive communities (WSUD 2018 & Hydropolis 2018), 12-15 February 2018, Perth, Western Australia p. 142-151
- Full Text:
- Reviewed:
- Description: The potential for stormwater to supplement traditional water supplies from upstream catchments or groundwater is high, with claims that the quantity of additional runoff from impervious surfaces in a modern city in a temperate climate is greater than the total potable water demand. To ensure the success of Integrated Urban Water Management, it must consider the broad context of catchment management and the cumulative effect of all factors including river health. Ballarat, an inland city of approximately 100,000 people in south-eastern Australia, has many attributes necessary to potentially exploit stormwater. Given the doubling of population, tripling of residences and 90% increase in average residence size over the past 60 years, over which time flow data is available for the downstream waterway, it might be expected that the flow in the river downstream of the city within the catchment would reflect additional stormwater runoff. However, no increase in flow was detected between 1957 and 1996 while flow over the past 20 years has reduced by 60%. A water balance shows this decrease was not due to extractions as the stream has been a consistent net receiver of water from other catchments. Modelling data from the Australian Water Resources Assessment indicates that the reduction in streamflow is double what might be expected due to climatic variations. Between 1957 and 1996 there was no significant difference between modelled runoff and actual flow, however from 1997 onwards there is a significant divergence. While lower runoff may be expected during the period of drought, the rainfall-runoff relationship does not return to previous levels during latter years of rainfall. The effect is greater during higher flow months, which has significance when identifying potential additional water resources. Base flow has been reduced to the point where dry weather flow is reliant on waste water treatment plant and mine discharge. This study indicates that while impervious surfaces generate higher runoff which can cause environmental damage, making stormwater an attractive water source, consideration must be given to the impacts on the whole catchment when assessing alternative supply options.
- Authors: Ebbs, David , Dahlhaus, Peter , Barton, Andrew , Kandra, Harpreet
- Date: 2018
- Type: Text , Conference paper
- Relation: 10th International Conference on Water Sensitive Urban Design: Creating water sensitive communities (WSUD 2018 & Hydropolis 2018), 12-15 February 2018, Perth, Western Australia p. 142-151
- Full Text:
- Reviewed:
- Description: The potential for stormwater to supplement traditional water supplies from upstream catchments or groundwater is high, with claims that the quantity of additional runoff from impervious surfaces in a modern city in a temperate climate is greater than the total potable water demand. To ensure the success of Integrated Urban Water Management, it must consider the broad context of catchment management and the cumulative effect of all factors including river health. Ballarat, an inland city of approximately 100,000 people in south-eastern Australia, has many attributes necessary to potentially exploit stormwater. Given the doubling of population, tripling of residences and 90% increase in average residence size over the past 60 years, over which time flow data is available for the downstream waterway, it might be expected that the flow in the river downstream of the city within the catchment would reflect additional stormwater runoff. However, no increase in flow was detected between 1957 and 1996 while flow over the past 20 years has reduced by 60%. A water balance shows this decrease was not due to extractions as the stream has been a consistent net receiver of water from other catchments. Modelling data from the Australian Water Resources Assessment indicates that the reduction in streamflow is double what might be expected due to climatic variations. Between 1957 and 1996 there was no significant difference between modelled runoff and actual flow, however from 1997 onwards there is a significant divergence. While lower runoff may be expected during the period of drought, the rainfall-runoff relationship does not return to previous levels during latter years of rainfall. The effect is greater during higher flow months, which has significance when identifying potential additional water resources. Base flow has been reduced to the point where dry weather flow is reliant on waste water treatment plant and mine discharge. This study indicates that while impervious surfaces generate higher runoff which can cause environmental damage, making stormwater an attractive water source, consideration must be given to the impacts on the whole catchment when assessing alternative supply options.
The journey to a water sensitive city - a case study of Ballarat, Victoria, Australia
- Ebbs, David, Kandra, Harpreet, Dahlhaus, Peter
- Authors: Ebbs, David , Kandra, Harpreet , Dahlhaus, Peter
- Date: 2016
- Type: Text , Conference paper
- Relation: 37th Hydrology & Water Resources Symposium 2016: Water, Infrastructure and the Environment p. 107-114
- Full Text: false
- Reviewed:
- Description: Water security is a vital part of ensuring a sustainable future. This is particularly true for many cities in Australia where relatively low rainfall, population growth and climate change places communities under water stress. The 'Water Sensitive City' is one in which water is drawn from a range of water supplies and that sustainably interacts with its surrounding environment. Every city has a unique water history in which the economic, environmental and social history have impacted on the development of water management. Tracking the evolution of water management of a city from its initial stages can provide information regarding the journey towards a Water Sensitive City. Water management in Ballarat has been tracked from the establishment of the first water supply to the city in the 1850's until 2015 using historical records from the local water authority. These records show that Ballarat generally followed the classical water development model with the introduction of water supply, sewerage and water treatment. Water use in Ballarat increased dramatically from 1941 until 1980, in line with increased standards of living as expected. However, after this time water use decreased despite continued population growth, and commercial water use decreased as a percentage of total use and external water use also declined. The reasons behind the decline in water use since 1980 may contain lessons that can be used in the establishment of Water Sensitive Cities.
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