Exploring a flow regime and its historical changes downstream of an urbanised catchment

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

Losing stormwater: 60 years of urbanisation and reduced downstream flow

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

Exploring the application of artificial neural network in rural streamflow prediction - A feasibility study

Streams and rivers play a critical role in the hydrologic cycle with their management being essential to maintaining a balance across social, economic and environmental outcomes. Accurate streamflow predictions can provide benefits in many different ways such as water allocation decision making, flood forecasting and environmental watering regimes. This is particularly important in regional areas of Australia where rivers can play a critical role in irrigated agriculture, recreation and social wellbeing, major floods and sustainable environments. There are several hydrological parameters that effect stream flows in rivers and a major challenge with any prediction methodology, is to understand these parameter interdependencies, correlations and their individual effects. A robust methodology is, thus, required for accurate prediction of streamflow under usually unique, waterway-specific conditions using available data. This research employs an approach based on Artificial Neural Network (ANN) to provide this robust methodology. Data from readily available sources has been selected to provide appropriate input and output parameters to train, validate and optimise the neural network. The optimisation steps of the methodology are discussed and the predicted outputs are compared and analysed with respect to the actual collected values. © 2018 IEEE.IEEE International Symposium on Industrial Electronic

Clogging of stormwater filters with high filtration rates

Hydraulic performance of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now increasingly used in management of polluted urban runoff. Clogging of filter media is recognised as a limiting factor of these stormwater treatment systems. However, very limited studies have been undertaken to understand clogging processes in the context of stormwater treatment systems. Of particular interest are non-vegetated high-flow rate filtration systems, which have the potential of maintaining high rate treatment at the same time as providing consistent and high pollutant removal. This thesis therefore focuses on the clogging of stormwater filters with high infiltration rates. The impacts of both design and operational variables on clogging have been studied in controlled laboratory environments using a compressed timescale approach. Laboratory investigations have also been made to assess the importance of biological clogging for these stormwater filters. Finally, observations from a field and modelling study of a filtration system located in Melbourne were compared with the findings from the laboratory studies. It was found that while angularity and smoothness of filter media may not be important for design, the flow rate through the stormwater treatment system is a key design aspect that needs to be considered. The infiltration rate of a system should be guided by the objectives of the system - whether to treat more volume of stormwater or to achieve better treatment performance, longevity and maintenance. The size of the filter media particles significantly impacted the clogging process, as well as the overall sediment removal performance of the filters. Deeper systems were found to have longer lifespan compared to shallower ones, even though the deeper systems removed more sediment over their life span. Having two layers of distinct sized media in the filter bed improved performance over the single-layered systems. Results suggest that sediment concentration in stormwater and size of sediments stormwater are important parameters that affect the performance and eventually longevity of these treatment systems. While hydraulic loading rate was found to be a significant parameter affecting the performance of these systems, any variation in the stormwater composition and loading regime had a limited effect. This study therefore developed an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs. It was also found that filters with enhanced biological conditions clogged faster as compared to filters with suppressed biological activity. Although the evidence was not overpowering, the variations observed in this study suggest that more attention should be given to biological clogging in stormwater filters, which is mostly ignored at present. Data from a field system using granular filters was collected and observations were compared with findings from laboratory studies. Similarities in evolution of infiltration performance in field based systems were observed. An exponential relationship between decline of infiltration rate and cumulative volume of treated stormwater to predict the system’s hydraulic performance was developed. This research has provided both theoretical and practical insights which will be useful in the application of stormwater infiltration systems that use filters with high infiltration rates for both stormwater harvesting and protection of receiving waters from stormwater pollution

Carbon offsetting in the road transport industry : issues and challenges of meeting the objectives

The overall performance of the transport industry is generally reported in terms of moving goods, or freight or people from any location to their final destination in a safe, reliable, cost-effective, and timely manner. However, greenhouse gas and exhaust fumes resulting from their operations has an adverse impact on climate and health of people living around transport corridors. Carbon dioxide (CO2) in exhaust fumes, if not contained, can cause poisonous air pollution and contributes to global warming. Australia's Department of Agriculture, Water and the Environment statistics predict that in 2030, CO2 emissions from the road transport industry through the usage of articulated and rigid trucks, are expected to grow by 37 percent from 2015 levels and is 80 percent higher compared to 2006 levels. In various parts of the world, there are annual mandatory road worthiness and exhaust testing requirements for responding to these problems. Some countries like Singapore (5.4 years) Luxembourg (6.5 years) and Austria (8.3 years), replace vehicles in five to 10 years on an average. Affordability, easy access, congestions, greenhouse gasses, impacts on health and safety are some of the important factors in asset management that can potentially impact climate change. Fleet asset management considers capital investments, operational and maintenance costs for informed decision making based on risks, life cycle costs and performances. This paper presents a review of studies on the impact of carbon offsetting on the transport infrastructure. Issues and challenges of alternative options for reducing risks and lifecycle costs along with approaches for enhancing performance covering reduction of greenhouse gasses and adverse impacts on human health have also been presented. © 2021 IEEE

Assessment of the impact of stormwater characteristics on clogging in stormwater filters

Hydraulic conductivity of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of stormwater characteristics on the clogging of stormwater filters. Effect of five different operational regimes has been tested in this study of sediment concentration; pollutant concentrations; stormwater sediment size; loading rate and stormwater loading/dosing regime and compared with the Base case. For each operational condition, five column replicates were tested. Results suggest that sediment concentration in stormwater is a significant parameter affecting hydraulic and treatment performance, eventually affecting longevity of these stormwater treatment systems. Further, the size of sediments (and their relation to the size of filter media grains) in stormwater was found to be an important parameter to be considered in design of coarse filters with high infiltration rates that are used for stormwater treatment. As expected, the addition of metals and nutrients had limited or no contribution to changes in hydraulic or sediment removal performance of the studied stormwater filters. Whilst loading rate was found to be an important parameter affecting the hydraulic and treatment performance of these systems, any variation in the stormwater loading regime had a limited effect on their performance. This study therefore develops an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs. © 2014, Springer Science+Business Media Dordrecht

Assessment of impact of filter design variables on clogging in stormwater filters

Stormwater filters are widely used in stormwater management, sometimes as standalone structures (e.g. stormwater filter beds), or as part of porous pavements, soak ways, infiltration basins and trenches. Due to the high levels of sediment present in stormwater, clogging is the main operational issue for these systems. A laboratory-based study was conducted to investigate the effect of filter bed design variables on the clogging phenomenon in non-vegetated stormwater filters with high infiltration rates. Design parameters studied include: filter media particle sizes (0.5 mm, 2 mm, 5 mm); depth of the filter bed (100 mm, 300 mm and 500 mm); and filter media packing configurations (layered or mixed). The size of filter media particles significantly impact the clogging process, as well as the overall sediment removal performance of the filters; filters with smaller particles had better sediment removal efficiency, but subsequently shorter lifespan. Deeper systems had longer lifespan compared with shallower ones, notwithstanding deeper systems removed more sediment over their life span. Having two layers of distinct sized media in the filter bed improved performance (e.g. volume of water treated; sediment removed) over the single-layered systems. However, the three-layered systems behaved similarly to two-layered systems. Mixed systems also showed improved performance, as compared with single-layered systems, and were similar to the three-layered systems. This study therefore suggests that simple modifications to a stormwater filtration system can help improve sediment removal performance and/or reduce maintenance intervals significantly, while only slightly affecting sediment removal performance. © 2014 Springer Science+Business Media Dordrecht

The journey to a water sensitive city - a case study of Ballarat, Victoria, Australia

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

Review of clogging processes in stormwater treatment filters

Clogging of infiltration systems has been defined as the process of decrease in permeability of a filtration system and occurs due to the accumulation of materials associated with treatment/sediment removal processes. Clogging of filter media is recognized as a limiting factor of these stormwater treatment systems. However, very limited studies have been undertaken to understand clogging processes in the context of non-vegetated stormwater treatment systems, especially high-flow-rate filtration systems. This chapters therefore focuses on a review of literature on the clogging of stormwater filters. This review summarizes both theoretical and practical insights, which will be useful in the application of stormwater infiltration systems that use filters with high infiltration rates for both stormwater harvesting and protection of receiving waters from stormwater pollution. The review concludes that it is vital to test performance of locally available filter media for stormwater treatment, such as pilot testing in demonstration facilities, design rather than just replicating knowledge from other water treatments.</p