A metabolism perspective on alternative urban water servicing options using water mass balance

Urban areas will need to pursue new water servicing options to ensure local supply security. Decisions about how best to employ them are not straightforward due to multiple considerations and the potential for problem shifting among them. We hypothesise that urban water metabolism evaluation based a water mass balance can help address this, and explore the utility of this perspective and the new insights it provides about water servicing options. Using a water mass balance evaluation framework, which considers direct urban water flows (both ‘natural’ hydrological and ‘anthropogenic’ flows), as well as water-related energy, we evaluated how the use of alternative water sources (stormwater/rainwater harvesting, wastewater/greywater recycling) at different scales influences the ‘local water metabolism’ of a case study urban development. New indicators were devised to represent the water-related ‘resource efficiency’ and ‘hydrological performance’ of the urban area. The new insights gained were the extent to which alternative water supplies influence the water efficiency and hydrological performance of the urban area, and the potential energy trade-offs. The novel contribution is the development of new indicators of urban water resource performance that bring together considerations of both the ‘anthropogenic’ and ‘natural’ water cycles, and the interactions between them. These are used for the first time to test alternative water servicing scenarios, and to provide a new perspective to complement broader sustainability assessments of urban water

Urban water security - what does it mean?

This research is focussed on understanding what urban water security means–a surprisingly elusive concept given the global shift from rural to urban living. We first make the case for a distinct urban water security definition. We then identify 25 unique water security definitions, of which three relate to the urban context but all with scope for improvement. Applying novel indices, we assess the prevalence, complexity and evolution of themes and dimensions within all definitions and find a stable spectrum of themes; but note a shifting emphasis towards environmental and social dimensions, away from quality and quantity of supply. Overall the definitions are becoming more comprehensive by simply listing more outcomes to be achieved. Instead of this ‘shopping-list’ approach, we propose a simplified urban water security definition with a focus on agreement of needs with community stakeholders, while using the themes to guide what the objectives might be

An inclusive city water account by integrating multiple data sources for South-East Queensland (SEQ), Australia

Cities are the hotspots of impacts on local and distant water resources through economic activity and consumption. More than half of the world's population lives in cities, which is expected to reach around two-thirds by 2050. Such a high level of increased urbanization calls for higher attention towards inclusive, safe, resilient, and sustainable cities (Sustainable Development Goals 11). To evaluate sustainability, inclusiveness, and resiliency pathways, a variety of sustainability indicators have been proposed, including the water footprint. The water footprint is defined as the total volume of freshwater used for the goods and services consumed. It covers both direct (e.g. drinking and cleaning) and virtual water flows (water used in the goods and services supply chain, hence also known as embedded water). Virtual water flows through products and services produced in other locations using their water resources influence the function, prosperity, and growth of the cities. Yet, this aspect is absent in the sustainability and strategic city water footprint reduction goals of Australian cities. To fully account for the water dependencies of Australian cities, direct and virtual water flows need to be known. To this purpose, we build inclusive city water of South-East Queensland (SEQ) by combining material flow analysis (MFA) and the multiregional input-output (MRIO) model. Water consumption in SEQ is used to quantify the water footprint on local water resources and net blue virtual water import. Together, this constitutes the water footprint on national water resources. Our results show that the water footprint of SEQ on local water resources is 620 GL with a net virtual water import of 1382 GL. Therefore, the water footprint of SEQ on national water resources is 2002 GL. The water footprint of SEQ on local water resources consists of direct water consumption by households (192 GL) and the industrial sector (428 GL). The consumed direct water of the SEQ industrial sector flows as virtual water to SEQ (149 GL), the rest of Australia (RoAUS) (all other regions except SEQ) (211 GL), and the rest of the world (68 GL). The virtual water inflows breakdown by source regions showed that 386 GL, 1019 GL, and 256 GL of virtual water imported from the major cities (Sydney, Melbourne, Adelaide, and Perth); regional areas of NSW, Victoria, and QLD; and RoAUS, respectively. Overall, the proposed inclusive city water account can enhance subnational estimates of city water footprint for benchmarking, as well as inclusive and resilient city water planning

Expert opinion on risks to the long-term viability of residential recycled water schemes: an Australian study

The water sector needs to make efficient and prudent investment decisions by carefully considering the long-term viability of water infrastructure projects. To support the assessment and planning of residential recycled water schemes in Australia, we have sought to clarify scheme objectives and to further define the array of critical risks that can impact the long-term viability of schemes. Building on historical information, we conducted a national survey which elicited responses from 88 Australian expert practitioners, of which 64% have over 10 years of industry experience and 42% have experience with more than five residential recycled water schemes. On the basis of expert opinion, residential recycled water schemes are considered to be highly relevant for diversifying and improving water supply security, reducing wastewater effluent discharge and pollutant load to waterways and contributing to sustainable urban development. At present however, the inability to demonstrate an incontestable business case is posing a significant risk to the long-term viability of residential recycled water schemes. Political, regulatory, organisational and financial factors were also rated as critical risks, in addition to community risk perception and fall in demand. The survey results shed further light on the regulatory environment of residential recycled water schemes, with regulatory participants rating the level and impact of risk factors higher than other survey participants in most cases. The research outcomes provide a comprehensive understanding of the critical risks to the long-term viability of residential recycled water schemes, thereby enabling the specification of targeted risk management measures at the assessment and planning stage of a scheme

Household analysis identifies water-related energy efficiency opportunities

Water heating accounts for around one third of household direct energy use. This energy demand is some four times greater than lighting. Here we use detailed monitoring and modelling of seven individual households to quantify major factors. Using normalized sensitivity results we demonstrate (i) high variability and (ii) a large and consistent influence of shower duration, flow rate, frequency and temperature along with hot water system efficiency, adult population, and the temperature of cold water. A 10% change in these factors influenced 0.1–0.9 kWh/hh-person.d, equivalent to a 2–3% of total household energy use. We draw on 5399 shower events from a further 94 households, and 491 shower temperature measurements to understand the scope for changes to the households. Individual parameters variation guided by these larger datasets demonstrated shower duration and flow rate offer most scope for change. The work helps guide city-scale analysis of household water-related energy demand. It also supports the tailoring of behavioural and technological water-efficiency programs towards those with strongest potential to influence energy. Strong interaction between parameters suggests that programs aiming to influence water-related energy need to be aware of how this interplay either amplifies, or diminishes, the intended energy savings

The effect of water demand management in showers on household energy use

This paper explores the range of potential energy use impacts of shower water demand management in a case study of five highly characterised households in Melbourne (Australia), and assesses the difference in energy and cost responses for four different hot water system types. Results show that a shift to four minute showers (from current durations of between six and ten minutes) would lead to a reduction of between 0.1 and 3.8 kWh p(-1) d(-1) in the households studied, comprising between 9% and 64% of baseline hot water system energy use. Contrasted with an average energy use for water service provision in Melbourne of 0.3 kWh p(-1) d(-1), such household reductions demonstrate significant potential for urban water cycle energy management. Combined water and energy (natural gas) cost savings in response to the four-minute shower scenario were $37 to$500 hh(-1) y(-1) in the households studied. Energy cost savings would be more significant for households with electric storage hot water systems than those with gas systems, at $39 to$900 hh(-1) y(-1), due to higher variable tariffs for electricity than natural gas in Victoria ($0.2678 kWh(-1) vs$0.0625 kWh(-1)). Households with electric storage hot water systems may therefore have greater financial incentive to participate in water-related energy demand management (assuming similar tariff structures). (c) 2017 Elsevier Ltd. All rights reserved

Energy use for water provision in cities

Energy demand for urban water supply is emerging as a significant issue. This work undertakes a multi-city time-series analysis of the direct energy use for urban water supply. It quantifies the energy use and intensity for water supply in 30 cities (total population of over 170 million) and illustrates their performance with a new time-based water-energy profiling approach. Per capita energy use for water provision ranged from 10 kWh/p/a (Melbourne in 2015) to 372 kWh/p/a (San Diego in 2015). Raw water pumping and product water distribution dominate the energy use of most of these systems. For 17 cities with available time-series data (between 2000 and 2015), a general trend in reduction of per capita energy use for water provision is observed (11%–45% reduction). The reduction is likely to be a result of improved water efficiency in most of the cities. Potential influencing factors including climate, topography, operational efficiency and water use patterns are explored to understand why energy use for water provision differs across the cities, and in some cities changes substantially over time. The key insights from this multi-city analysis are that i) some cities may be considered as benchmarks for insight into management of energy use for water provision by better utilising local topography, capitalising on climate events, improving energy efficiency of supply systems, managing non-revenue water and improving residential water efficiency; ii) energy associated with non-revenue water is found to be very substantial in multiple cities studied and represents a significant energy saving potential (i.e. a population-weighted average of 16 kWh/p/a, 25% of the average energy use for water provision); and iii) three Australian cities which encountered a decade-long drought demonstrated the beneficial role of demand-side measures in reducing the negative energy consequences of system augmentations with seawater desalination and inter-basin water transfers

Global socio-economic losses and environmental gains from the Coronavirus pandemic

On 3 April 2020, the Director-General of the WHO stated: “[COVID-19] is much more than a health crisis. We are all aware of the profound social and economic consequences of the pandemic (WHO, 2020)”. Such consequences are the result of counter-measures such as lockdowns, and world-wide reductions in production and consumption, amplified by cascading impacts through international supply chains. Using a global multi-regional macro-economic model, we capture direct and indirect spill-over effects in terms of social and economic losses, as well as environmental effects of the pandemic. Based on information as of May 2020, we show that global consumption losses amount to 3.8$tr, triggering significant job (147 million full-time equivalent) and income (2.1$tr) losses. Global atmospheric emissions are reduced by 2.5Gt of greenhouse gases, 0.6Mt of PM2.5, and 5.1Mt of SO2 and NOx. While Asia, Europe and the USA have been the most directly impacted regions, and transport and tourism the immediately hit sectors, the indirect effects transmitted along international supply chains are being felt across the entire world economy. These ripple effects highlight the intrinsic link between socio-economic and environmental dimensions, and emphasise the challenge of addressing unsustainable global patterns. How humanity reacts to this crisis will define the post-pandemic world