Urban water metabolism indicators derived from a water mass balance – Bridging the gap between visions and performance assessment of urban water resource management

Accepted Manuscript Urban water metabolism indicators derived from a water mass balance – bridging the gap between visions and performance assessment of urban water resource management

M.A. Renouf, S. Serrao-Neumann, S.J. Kenway, E.A. Morgan, D. Low Choy PII:

S0043-1354(17)30424-4

DOI:

10.1016/j.watres.2017.05.060

Reference:

WR 12939

To appear in:

Water Research

Received Date:

17 December 2016

Revised Date:

11 May 2017

Accepted Date:

28 May 2017

Please cite this article as: M.A. Renouf, S. Serrao-Neumann, S.J. Kenway, E.A. Morgan, D. Low Choy, Urban water metabolism indicators derived from a water mass balance – bridging the gap between visions and performance assessment of urban water resource management, Water Research (2017), doi: 10.1016/j.watres.2017.05.060

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ACCEPTED MANUSCRIPT 1 2 3

Urban water metabolism indicators derived from a water mass balance – bridging the gap between visions and performance assessment of urban water resource management

4

Renouf, M.A.a,c, Serrao-Neumann, S., b,c Kenway, S.J. a,c, Morgan, E.A. b,c, Low Choy, D. b,c

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a

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achieving sustainable urban areas, but to date it has been difficult to quantify performance

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indicators to help identify more sustainable outcomes, especially for water resources. In this

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work, we advance quantitative indicators for what refer to as the ‘metabolic’ features of

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urban water management: those related to resource efficiency (for water and also water-

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related energy and nutrients), supply internalisation, urban hydrological performance,

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sustainable extraction, and recognition of the diverse functions of water. We derived

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indicators in consultation with stakeholders to bridge this gap between visions and

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performance indicators. This was done by first reviewing and categorising water-related

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resource management objectives for city-regions, and then deriving indicators that can gauge

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performance against them. The ability for these indicators to be quantified using data from an

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urban water mass balance was also examined. Indicators of water efficiency and hydrological

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performance (relative to a reference case) can be generated using existing urban water mass

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balance methods. In the future, complementary indicators for water-related energy and

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nutrient efficiencies could be generated by overlaying the urban water balance with energy

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and nutrient data. Indicators of sustainable extraction will require methods for defining

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sustainable extraction rates.

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Keywords: resource efficiency, water efficiency, water-related energy, nutrients, urban

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hydrology, sustainability

School of Chemical Engineering, University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia Cities Research Centre, Griffith University, Nathan, Queensland 4111, Australia c Cooperative Research Centre for Water Sensitive Cities, Monash University, Victoria, 3800, Australia. b

Corresponding author. Email: [email protected]

Abstract: Improving resource management in urban areas has been enshrined in visions for

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1. Introduction

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A number of programs report and benchmark the performance of water management in

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urban areas using sets of indicators. These include, inter alia, the City Blueprint (van

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Leeuwen et al. 2012), the Water Sensitive Cities Index (CRC WSC 2016), the Sustainable

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Cities Index (Arcadis 2016), the Asian Water Development Outlook (ADB 2016), and the

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Green Cities Index (EIU 2009, 2011). These programs help highlight the broad challenges for

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urban water management in urban areas at different stages of economic development, for

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setting benchmarks, and for inferring areas for improvement.

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In parallel, there is a range of documents that contain the visions and principles for urban

39

water management set by urban water industry bodies and international development

40

agencies. These include the International Water Association (IWA 2016), the OECD (OECD

41

2015), the Asian Development Bank (ADB 2013, 2016), the UK Water Partnership (UK

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Water Partnership 2015), and the Australian CRC for Water Sensitive Cities (Wong et al.

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2013). While the visions are articulated in different ways (Table A1), some consistencies are

44

evident in the key objectives, including access to water and sanitation, supply security,

45

environmental protection, the functionality of urban water, risk management of extreme

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conditions (resilience to droughts and floods) and institutional aspects (Table 1). They focus

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on the management of direct water (real flows of water from surrounding regions) and not on

48

indirect water (that embodied in the goods and services produced using water from

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elsewhere) (Renouf and Kenway 2016).When existing performance indicators are compared

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to the objectives derived from the vision statements (Table 1) we find a misalignment.

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Indicators seem to have been driven by data availability, and not systematically derived from

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overarching goals. Exceptions are the Water Sensitive Cities Index (Beck et al. 2016), which

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includes a range of indicators that align with the desired features of ‘water sensitive cities’,

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and the ADB’s Asian Water Outlook which has a set of indicators aligned to its goals.

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However, the indicator outputs from these instruments are not currently able to be empirically

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quantified, and are evaluated qualitatively.

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In this work, we are specifically interested in resource management objectives of urban

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water management. This includes supply security (which encompasses resource efficiency

59

and internalisation of supply), protection of water resources (which encompasses sustainable

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management of fresh and estuarine water resources and restoration of hydrological flows),

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and recognising the diverse functionality of urban water (Table 1). We label these to as

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‘metabolic’ characteristics, where water metabolism (in the urban context) refers to how

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effectively urban areas utilise water from the perspective of the urban area as a whole

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(Renouf and Kenway 2016). We aim to derive quantitative indicators of urban water

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metabolism that align with articulated urban water management objectives. Without such

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indicators it is difficult to measure how well urban areas are progressing towards their

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resource management objectives.

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To address this gap in indicators, we developed a conceptual basis for urban water

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metabolism indicators, and investigated how they could be quantified using the data

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generated from an urban water mass balance. In developing this ‘wish list’ of indicators, we

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also considered the practice needs of stakeholders who may use the indicators for both water

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and regional and urban planning applications. The questions asked were: What could be an

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ideal set of urban water metabolism indicators? Which indicators can be quantified using data

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from an urban water mass balance analysis? How can they align to the practice needs of the

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users? Performance indicators are relevant at many urban scales (neighbourhoods, precincts,

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whole cities), but we are most interested in the larger city-region scale, which is the scale at

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which strategic planning for water resources management needs to occur (Vietz et al. 2016,

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Walsh et al. 2005a). Table 1 Alignment between urban water management objectives and performance indicators

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Water mass balance has been advocated for some time for the detailed study of urban water

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(McPherson 1973), and has found application in urban metabolism studies (examples are

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Farooqui et al. (2016) and Thériault & Laroche (2009)) and urban hydrological studies

83

(examples are Haase (2009) and Barron et al. (2013)). An urban water mass balance

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quantifies all flows and fluxes of water (both managed and natural) into, through, and out of a

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defined urban boundary (Kenway et al. 2011a). It is useful for framing indicators of urban

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water metabolism because of the big-picture perspective it provides, and the

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comprehensiveness and accuracy that the mass balance drives (Renouf and Kenway 2016).

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Other methods have also been used for estimating and simulating aspects of urban water

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systems at larger urban scales. These involve the up-scaling of integrated urban water system

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modelling, which are traditionally undertaken at smaller urban scales (Behzadian and

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Kapelan 2015, Makropoulos et al. 2008, Rozos and Makropoulos 2013, Urich et al. 2013,

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Venkatesh et al. 2014). These methods typically generate indicators related to urban water

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system performance such as operating performance or environmental impacts. Urban water

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mass balance was chosen over these other methods as a source of data for urban water

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metabolism indicators because it generates data pertaining to the urban area as a whole

96

(Renouf and Kenway 2016), and is also a quicker and more accessible means of generating a

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general picture of urban water management.

98

The derivation of water metabolism indicators from an urban water mass balance is in its

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infancy. Past research in this area has focused on components of the water balance, for

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instance potable water supply (Kennedy et al. 2014), or the demand-supply balance of water 4

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systems (Sahely et al. 2005), or focused on one particular performance objective such as

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efficiency (Haie and Keller 2012). Previous studies have derived indicators from a whole of

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urban area water balance in the Australian context, with the indicators driven by what data

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was available (Farooqui et al. 2016, Kenway et al. 2011a). These indicators included total

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water use intensity of the urban area, the degree of supply internalisation, and the degree of

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departure from pre-development hydrological flows.

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We built on this prior work to develop a more comprehensive set of urban water

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metabolism indicators than is currently available. The novel contributions are (i) a review and

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categorisation of water-related resource management objectives for urban areas, (ii) the

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systematic derivation of indicators that can gauge performance against these objectives, and

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(iii) an assessment of how they can be quantified using an urban water mass balance.

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The intent is to advance our understanding of urban water performance from one based on

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the current business-as-usual approach, towards a new paradigm for urban water, which is

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inherent in the reviewed visions but not yet operationalised in performance indicators. The

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business-as-usual approach has focused on water supply and demand. The new paradigm

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recognises limits to natural resources and increased uncertainty and variability, particularly

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with regard to climate (Pahl-Wostl 2008). It requires a shift towards deriving highest value

118

from water, as opposed to taking and allocating what water is available from the

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environment. This requires a shift in thinking around how we interpret performance. For

120

example, the current paradigm considers water efficiency in terms of units of centralised

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water supply per person. In a future where the value of water is viewed more holistically with

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recognition of it multiple functions, this will morph towards efficiency based on the

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functionality of the water per unit of water. To achieve this will require many changes: a shift

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in governance, infrastructure design, and urban design, as well as a significant shift how

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people value water. 5

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2.1 Method overview

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management objectives (2.2), then determining how best to represent them as performance

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indicators (2.3), and then testing whether and how they may be quantified from an urban

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water mass balance (2.4). Consultation was undertaken with potential users to consider how

132

the indicators may align with their practice needs (2.5).

133 134

2.2 Categorisation of urban water management objectives

The set of urban water metabolism indicators was derived by first categorising urban water

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Indicators development was guided by the visions and/or principles articulated in the

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concept of Water Sensitive Cities (Wong et al. 2013), the International Water Association’s

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Water Smart Cities program (IWA 2016), the OECD’s framework for city-level water

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management, the ADB’s Water Development Outlook (ADB 2016), and UK’s Water

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Partnership (2015). The contents and themes of these visions are summarised in Appendix A

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(Table A1).

141

Key objectives inferred from these visions were categorised (see Table 1). They include

142

aspects that we label as urban water metabolism, but also risk management (resilience and

143

flood risk) and institutional aspects. We focused only on the urban water metabolism

144

objectives of:

145

 resource efficiency, which is the efficient use of water-related resources, not only water

146

but also energy for moving and treating water, and the nutrients mobilised in water. Water

147

efficiency here refers to the overall water efficiency of the urban area in relation to water

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drawn from the environment, and not the water use efficiency of end users.

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 supply internalisation aims to extend supplies and decrease reliance on water drawn from

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the environment by utilising water sources available within the urban area, i.e. harvesting

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and utilising water falling on urban areas (rainwater, stormwater) and the recycling of

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water (wastewater, greywater);

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 protection of water resources and hydrological flows, refers to the sustainable

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management of water resources in terms of stocks, qualities and flows. This means: (i)

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managing the volumes of water drawn from the environment for urban uses within the

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region’s capacity to supply, (ii) limiting the discharge of pollutants to the environment to

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maintain the quality of waterways, and (iii) restoring natural hydrological flows altered

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by increased imperviousness, i.e. reducing stormwater runoff, increasing infiltration and

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increasing evapotranspiration; and

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 recognising the diverse functions of water beyond just meeting primary needs for potable

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water. This can include social functions (e.g. urban liveability, recreation, cultural),

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provision for environmental flows within urban catchments to sustain habitat health and

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biodiversity, enabling economic activities (e.g. industrial, commercial, energy generation,

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agricultural, forestry, fisheries, livestock), and supporting a range of urban spaces (e.g.

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green infrastructure, vegetation and green open space for amenity, recreation and urban

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heat island mitigation).

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2.3 Derivation of urban water performance indicators

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The aim was to generate indicators that gauge water metabolism performance against the

169

objectives, and not be constrained by what can practicably be measured with available data.

170

Thus, the derived indicators were considered a ‘wish list’, with an expectation that some may

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not be quantifiable at present, but are nonetheless important to assess urban water resources

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management.

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2.4 Quantification of urban water performance indicators

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Quantification of the indicators was tested using urban water mass balance method that was

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originally described by Kenway et al. (2011a), further developed by Farooqui et al. (2016), 7

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and also used by Marteleira et al. (2014). It generates an account of all water flows and fluxes

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into and out of a defined urban area (both in the natural and managed water cycles), and

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including changes in water storage, such that the sum of inflows equals the sum of outflows

179

plus change in storage (Figure 1). The data populated into the water mass balance are

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estimates of annual average volumetric flows and fluxes of water (GL/yr).

181

Extensions to this method were made to support the quantification of the indicators. The

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first was to account for flows of water to the various uses/functions of water within the urban

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system, instead of just accounting for flows and fluxes into and out of the urban system. This

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was to support the generation of indicators related to recognising the diverse functions of

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water. The second was to quantify the water-related energy use and nutrient loads associated

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with the water flows. This was to allow consideration of the wider resource management

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implication of urban water systems to support the generation of indicators related to resource

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efficiency.

189 190 191 192 193 194 195 196

Figure 1. Extended urban water mass balance Notes: Based

on an approach originally described by Kenway et al. (2011a) and further developed by Farooqui (2016). Blue arrows are natural hydrological flows, and yellow arrows are anthropogenic flows managed by urban water infrastructure.

2.5 Stakeholder validation of indicators

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The aim of the stakeholder validation was to understand the practice needs of stakeholders

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in relation to urban water management aspects that influence decision making and

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implementation of planning policies, especially towards improving water resource

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management at the city-region scale. Stakeholder validation was undertaken in three

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Australian capital city-regions – South East Queensland region, Melbourne metropolitan

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region and Perth metropolitan region. Semi-structured interviews were conducted with

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purposely-selected stakeholders (Zhang and Wildemuth 2009) from government (state and

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local government) and non-government agencies with direct and indirect roles in urban water

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management, natural resource management and urban and regional planning. Fourteen

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interviews involving sixteen stakeholders were conducted between September and November

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2016. Interviews lasted around one hour, were audio recorded and transcribed verbatim.

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Feedback was sought from interviewees about information needs for advancing the four

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identified water metabolism objectives of: (i) resource efficiency; (ii) supply internalisation,

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(iii) protection of water resources and hydrological flows, and (iv) recognising the diverse

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functions of water (see Table 2 for details). In-depth content analysis (Bowen and Bowen

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2008) was performed to extract information related to the applicability and relevance of

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performance indicators to their professional roles. 3. Results and discussion

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Table 2 details the water metabolism indicators that were derived for each of the urban water

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management objectives, along with how they can be quantified using an urban water mass

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balance, and how they can align with the practice needs of users.

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Table 2 Proposed urban water metabolism indicators

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3.1 Resource efficiency

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Resource efficiency is an objective in all the urban water visions reviewed (Table A1). It

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mostly relates to the efficient use of water, but there are also objectives for the efficient use

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and management of water-related energy and nutrients. Energy use and nutrient mobilisation

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are important aspects of urban water management, and concurrent consideration of all three is

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important for avoiding inadvertent trade-offs when solutions for one results in problems for

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the other. So indicators are proposed for all three dimensions (Table 2).

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The inferred intent of efficiency is to reduce the amount of resource used per unit of function,

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or maximise the function delivered per unit of resource use.

So efficiency is usually

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expressed as resource use per unit of function, or the function per unit of resource use. The

229

functional unit for urban water is difficult to define in the context of an urban area. If only the

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water supply and sewerage service is being considered, then the function delivered is fairly

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straightforward – a water service per person. However, in the context of the urban area itself,

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water in both the natural and managed water cycles has more diverse functions, also enabling

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amenity and liveability (recreation, green space, mitigating urban heat), environmental

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services, and economic production (energy, agriculture, manufacturing). Ideally the

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functional unit for should relate to the functions (or ‘services’) that water delivers. However,

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in the current absence of such an index, we use the population serviced as a proxy for

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function.

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3.1.1

Water efficiency

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Water efficiency in the urban context commonly refers to water efficiency of the end user

240

(for example residential water use per person – GL/person/yr). From an urban metabolism

241

perspective, we use the term in the context of the urban area as a whole, with the inferred

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intent of reducing input of water drawn from the local environment (‘environmental’ water)

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to supply the direct water needs of urban populations. The urban water efficiency indicators

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propose to represent the overall efficiency of water in the urban area.

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Indirect urban water use drawing on global supplies, is not accounted for in this current

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framework. Other authors have suggested that both direct and indirect water use be

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considered in water efficiency indicators (Huang et al. 2013, Paterson et al. 2015). We

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differentiate the two at this stage and focus on direct water use so it can be evaluated against

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the local resource constraints (Renouf and Kenway 2016). Their integration is a future

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opportunity that requires further research.

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An achievable indicator is to express the direct water efficiency of whole of urban area per

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population serviced. However, as noted earlier, an aspirational indicator would be to express 10

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it per unit of functionality. Efficiencies can be achieved by reducing water demand (internal

254

efficiency) and/or sourcing fit for purpose water (rainwater, stormwater, wastewater) from

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within the urban system (internalisation of supply).

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Water resource managers currently do not manage urban water with the intent of reducing the

257

use of environmental water, except in periods of drought. Instead, they manage the allocation

258

of available water. This means that allocations are assigned to urban uses, productive uses

259

(agriculture, energy) and environmental flows based on the available yield of water from the

260

water supply catchment,. This is an ‘allocate all that is available’ approach. In this context the

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interpretation of water efficiency would be the population or activity that can be supported by

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the urban allocation of water. In contrast, the metabolism interpretation of water efficiency is

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an ‘only take what is needed’ approach by optimising internal efficiency and internalisation

264

of supply.

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Stakeholders identified the role of water efficiency indicators for supporting evidence-based

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policy for advancing urban and building design and green/open space planning (see Table 2).

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They provide mechanisms for evaluating how urban development (infill and greenfield)

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influence water efficiency of the region as a whole.

269

3.1.2

270

Water-related energy refers to energy used to pump, treat, and dispose of water, but also in

271

the use phase (heating, cooling etc.), the latter being more significant in scale than the former

272

(Kenway et al. 2011b). Its quantification is important for understanding the potential energy

273

trade-offs for water supply options, or urban energy saving opportunities.

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The water-related energy efficiency indicator proposes to represent the energy intensity

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across the urban water system. It can be accounted for as an overlay to the water mass

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balance, to generate the total water-related energy intensity of urban water system (see Figure

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1), and the feasibility of this has been demonstrated by Farooqui et al. (2016).

Water-related energy efficiency

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Water and energy efficiencies are usually not coupled in urban and regional planning

279

processes. Stakeholders identified that they can support the business case for water sensitive

280

interventions by factoring in energy savings (Table 2). They can also foster policy innovation

281

towards greater collaboration between government and government-owned agencies in the

282

water and energy sectors.

283

3.1.3

Water-related nutrient efficiency

284

Water-related nutrient efficiency refers to the extent to which nutrients mobilised in

285

wastewater and stormwater runoff (nitrogen and phosphorous), are recovered and reused. An

286

example is the utilisation of wastewater for agricultural irrigation, for which the reuse and

287

avoided discharge of nutrients is an important when considering the value of wastewater

288

recycling.

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The nutrient efficiency indicator (Table 2) proposes to represent the proportion of nutrient

290

loads (nitrogen and phosphorous) in wastewater and stormwater that are recovered and

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utilised within the urban system. Its quantification will require an urban nitrogen and

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phosphorous balance as an overlay of the water mass balance. There are few examples of this

293

having been conducted at the whole of urban area scale (Walker et al. 2012), and so this is an

294

aspirational indicator that would need to be progressed once practical methods for urban

295

nutrient balances have been developed.

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Nutrient offset schemes based on nutrient pricing are starting to emerge to promote the

297

reduction of excess nutrients entering waterways for improved water quality. Stakeholders

298

noted the value of nutrient efficiency indicators for not only informing these schemes but also

299

driving policy innovation that supports less-polluting industry activities and urban

300

development. Furthermore, they can provide guidance for investment strategies (e.g. upgrade

301

of existing wastewater treatment plants) in relation to the scale of nutrient recovery needed to

302

occur to achieve best economic and environmental outcomes. 12

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3.2 Supply internalisation

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Water supply internalisation is the extent to which water is sourced internally within the

305

urban system, for example rainwater and stormwater collection, or wastewater recycling. It is

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an objective of all the reviewed urban water visions (Table A1). Internal water sources are

307

seen not only as a means of reducing reliance on externally-sourced water supplies, but the

308

facilities for collecting water (as in the case of stormwater harvesting) can also provide flood

309

retention and amenity.

310

The internalisation indicator (Table 2) proposes to represent the proportion of water

311

demand met by internally harvested or recycled water. Its quantification is currently

312

achievable using data generated by the urban water mass balance, because the water mass

313

balance accounts for all water supplies.

314

The supply diversification that internalised supplies provide can help deal with climatic

315

uncertainty and natural variability, a critical challenge to city-regions worldwide.

316

Stakeholders highlighted the relevance of indicators that can monitor this for determining

317

priorities for water supply infrastructure delivery and upgrade (e.g. centralised vs.

318

decentralised systems) as well as supporting technological innovation (e.g. seasonal storage

319

options in drier locations). They can build a case for regulatory or voluntary interventions.

320

3.3 Protecting water resources and hydrological flows

321

All the reviewed visions of urban water management contain objectives for protecting

322

water resources, which include (i) protection stocks of surface and groundwater resources

323

through sustainable use, (ii) protection water quality through the management of pollutant

324

discharges, nutrients in particular, and (iii) restoration of natural hydrological flows.

325

3.3.1

Water use within safe operating space

326

The sustainable management of water resources has been a long-standing objective of

327

regional water resource management, through the allocation of available surface and ground

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waters to various functions. As freshwater supplies become stretched due to population

329

growth and climate change, some urban areas face reductions in water allocations. So it is

330

increasingly important to consider urban water use relative to what the supplying region can

331

provide, now and in the future, within a safe operating space. The safe operating space for

332

water enables enough water to sustain moisture feedbacks, provides supporting ecosystem

333

functions and services, and secure water resources for aquatic ecosystems (Rockström et al.

334

2009).

335

The water use within safe operating space indicator proposes to represent the urban water

336

use relative to a sustainable urban water allocation (surface waters or ground waters). A ratio

337

>1 means that urban use of water is greater than the sustainable rate, and the urban system is

338

not functioning within a safe operating space. A ratio <1 means that urban water use is less

339

than the sustainable rate, and the urban system is functioning within the safe operating space.

340

Water resource managers derive urban water allocations after accounting for required

341

environmental flows, but it is not clear if that is a true reflection of what can be sustainably

342

extracted from the environment. As the derivation of sustainable urban water allocations is an

343

evolving science this is an aspirational indicator for future development.

344

Stakeholders pointed to the importance of these performance indicators for improving how

345

water allocation is carried out at the city-region scale. They would also allow planners to

346

gauge the extent to which proposed urban developments contribute to the sustainability of

347

water extraction and set benchmarks.

348

3.3.2

Water pollutant loads within safe operating space

349

An indicator of the stress that urban areas place on the water quality of the supporting

350

region is also proposed (Table 2). It is based on the load of nutrients (nitrogen and

351

phosphorus) discharged from the urban system relative to the estimated assimilative capacity

352

of receiving waterways. Its quantification will require an urban nitrogen and phosphorous 14

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balance as an overlay to the water mass balance to estimate the potential discharge loads.

354

There are no examples of this having been conducted at the city-region scale. Furthermore,

355

assimilative capacities will need to be better understood. So this is an aspirational indicator

356

requiring further method development.

357

Water sensitive urban design (WSUD) in being implemented worldwide to improve urban

358

water quality. Stakeholders identified the role of these indicators for monitoring the

359

efficiency and benefits of WSUD initiatives at a city-region scale. This would subsequently

360

inform the regulatory frameworks that enable their implementation and inform investment

361

decisions.

362

3.3.3

Hydrological performance

363

It is widely recognised that urbanisation changes natural hydrological flows (Livingston

364

and McCarron 1992). Increased imperviousness augments stormwater flows and degrades

365

urban stream health (Walsh et al. 2005b), reduces evapotranspiration contributing to urban

366

heat island effect (Coutts et al. 2014), and reduces infiltration inhibiting natural groundwater

367

recharge. All urban water visions promote mitigation of these adverse effects by reducing

368

stormwater runoff, increasing evapotranspiration through urban vegetation and increasing

369

infiltration (Table A1).

370

The hydrological performance indicators propose to represent the degree of departure from

371

pre-development hydrological flows, as the ratio of post- to pre-urbanised flows, for

372

stormwater runoff, evapotranspiration, and infiltration to groundwater (Table 2). A ratio >1

373

means that the magnitude of the annual flow/flux is larger than pre-developed landscape, and

374

a ratio <1 means it is smaller. The intent of the indicators is to gauge whether urban

375

hydrological flows are being maintained at or restored to some ‘near-natural’ or ‘pre-

376

urbanised/developed’ reference state.

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Their quantification is currently achievable using data generated by an urban water mass

378

balance, which accounts for all hydrological flows, has been demonstrated by Farooqui et al.

379

(2016). They require the hydrological flows for the pre-urbanised state (or other point of

380

reference) to be estimated. A critical factor therefore is the definition of the ‘pre-urbanised’

381

reference state. That task in itself is useful for understanding what the desired end point is.

382

Similar to performance indicators for water quality, indicators for hydrological

383

performance are identified by stakeholders to being instrumental in supporting policy

384

implementation that seeks innovation in urban design, informs investment options, and builds

385

cases for flexible and regulatory mechanisms to achieving improved environmental

386

outcomes.

387

3.4 Recognising the diverse functionality of water

388

In some urban water visions (e.g. Water Sensitive Cities) there is recognition of the diverse

389

functions of water in the urban landscape. The functions that water provides in the urban

390

landscape are context specific and may include social functions (human consumption,

391

recreation, cultural), environmental functions (habitat health, biodiversity), urban space

392

functions (green infrastructure, green open space, heat island mitigation) and economic

393

functions (industrial, commercial, energy generation, agriculture, fisheries, livestock)

394

(Ferguson et al. 2013, Gulickx et al. 2013, Jiménez Cisneros et al. 2014). It is not clear how

395

to quantify functionality, but we suggest a first step is to account and budget for water needed

396

to maintain these functions within the urban water allocation.

397

The functionality indicator proposes to represent the extent to which the water budgeted or

398

allocated to each functions is sufficient to maintain each function (Table 2). It is a ratio of the

399

amount of water needed relative to the amount of water actually allocated. A ratio >1 means

400

that less water is allocated to the function than is needed, and a ratio <1 means the more

401

water is allocated than needed. 16

ACCEPTED MANUSCRIPT 402

Stakeholders were particularly interested in these performance indicators because they

403

directly relate to two emerging concepts in urban and regional planning and water resource

404

management, that of multi-functionality (Ashley et al. 2011, Selman 2009) and liveability

405

(Badland et al. 2014, WSAA 2014). In particular, stakeholders highlighted the importance of

406

such indicators for informing policy that guides urban design and land use development.

407

They also pointed to their role in policy innovation in the urban planning that also accounts

408

for blue infrastructure (Greenway 2015, Macháč et al. 2016) as a form of public open space

409

that can have multiple benefits, such as human health related benefits (e.g. recreation, sport

410

activities, social interaction) and water quality benefits (e.g. retention of pollutants).

Conclusions 411

A categorised set of urban water management objectives was developed, guided by the

412

visions for direct urban water management articulated by urban water peak bodies and

413

international development agencies. This categorisation helps provide consistency of

414

terminology and meaning to facilitate common goals for water utilities and the city-regions

415

they support.

416

Based on this categorised set of objectives, a ‘wish list’ of performance indicators for

417

resource management aspects of urban water was devised. It contains indicators for resource

418

efficiency (water and water-related energy use and nutrient recovery), supply internalisation,

419

protection of water resources and hydrological flows, and recognising the diverse functions

420

of water. We labelled these as ‘water metabolism’ characteristics, because they relate to how

421

effectively an urban area utilises and manages water and water-related resources. They

422

emphasise the water performance of urban areas as a whole, rather than the water system

423

components within it, and recognise the connections between urban systems and their local

424

supporting regions.

17

ACCEPTED MANUSCRIPT 425

Indicators were validated by stakeholders from both urban and regional planning and water

426

resource management sectors with a range of applications being identified, including

427

supporting policy implementation and innovation related to urban design and land use

428

development, informing investment strategies, and mechanisms to benchmark the

429

performance of water resource management and urban development projects.

430

Quantification of some of the indicators is currently achievable using data generated using

431

existing urban water mass balance methods – water efficiency and hydrological performance.

432

Other ‘aspirational’ indicators will require further method development, including overlaying

433

the urban water balance with energy and nutrient data, the development of an urban water

434

functionality index to enable efficiency indicators to expressed per unit of function, and an

435

understanding the sustainable water yields and assimilative capacities of supporting regions.

436

The aspirational indicators can help guide the development of new frameworks and models to

437

guide urban water management, encouraging moves away from only thinking about what is

438

currently measurable. Deriving them from visions and objectives that underlie shifts to more

439

sustainable water management helps ensure they will be relevant to planners and water

440

managers.

441

The proposed water metabolism indicators bridge a gap between the visions for urban

442

water management and performance assessment. The specific contributions are (i) the

443

categorisation of water-related resource management objectives for urban areas, (ii) the

444

systematic derivation of indicators that can gauge performance against these objectives, and

445

(iii) an assessment of how they can be quantified using an urban water mass balance. The

446

work also advances our understanding of urban water performance from one based on the

447

current business-as-usual approach, towards the new paradigm for urban water.

18

ACCEPTED MANUSCRIPT Acknowledgements 448

The work was supported by Cooperative Research Centre for Water Sensitive Cities (CRC

449

WSC) in Australia, as part of Project B1.2. The contributions of Marguerite Renouf, Silvia

450

Serrao-Neumann and Ed Morgan were funded by the CRC WSC. Steven Kenway’s

451

contribution was funded by the Australian Research Council (DECRA funding

452

DE160101322). The authors acknowledge Julie Allen for her review of early drafts, and

453

thank the anonymous reviewer for their helpful comments.

454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494

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(2016) Thinking outside the channel: Challenges and opportunities for protection and restoration of stream morphology in urbanizing catchments. Landscape and Urban Planning 145, 34-44. Walker, R.V., Beck, M.B. and Hall, J.W. (2012) Water - and nutrient and energy - systems in urbanizing watersheds. Frontiers of Environmental Science & Engineering 6(5), 596–611.

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ACCEPTED MANUSCRIPT Table 1 Alignment between urban water management objectives and performance indicators Objectives for urban water management, derived from vision statements Water metabolism characteristics

569

Water Sensitive Cities Index (CRC WSC 2016)









Sustainable Cities Water Index (Arcadis 2016)











Asian Water Development Outlook (ADB 2013, 2016)













Finance mechanisms



Governance



Reduced flood risk



Resilience to droughts and floods

City Blueprint (van Leeuwen et al. 2012)

Recognising diverse functions of water (liveability, productivity, agriculture)



Restoration of natural hydrological flows



Resource efficiency (energy, nutrients)

Green City Index (EIU 2009, 2011)

Supply internalisation (self-sufficiency)

Urban water performance benchmarking programs

Institutional aspects

Integrated management

Risk management

Engagement with community

Funct -ionality

Economic sustainability

Protection of water resources (stocks and quality)

Environmental protection

Resource efficiency (water)

Supply security

Universal access to water and sanitation

Access to water

 



 





    



Notes:  = quantitative indicators;  = qualitative indicators

570

22

Table 2 Proposed urban water metabolism indicators Key objectives of urban water performance1 Resource efficiency

Water efficiency

Energy efficiency (water-related)

Performance indicators and their quantification2 Currently achievable Aspirational Urban water efficiency per person Urban water efficiency per unit of functionality - total use of ‘environmental’ water per person - total use of ‘environmental’ water per unit of urban function C C Population Functionality index Water-related energy efficiency per person - total energy use for the water system per person ETOT Population

Nutrient efficiency (water-related)

Supply internalisation

Protecting water resources and hydrological flows

Water-related energy efficiency per unit of functionality - total energy use for the water system (including the use phase) per unit of functionality ETOT Functionality index Nutrient recovery from urban water - proportion of the nutrient load in wastewater that is beneficially utilised NR Nw

Water supply internalisation - proportion of total water demand met by internally harvested / recycled water D+R D + R +C Water stocks (quantity)

Water quality

Applicability of indicators in practice3  Evidence-based policy planning and implementation (e.g. green/open space planning, human health, land-use control and development, integrated water management, building design)  Metrics to benchmark both water resource management and development performance (e.g. water management objectives, clarification of agencies roles and responsibilities, fit for purpose water demands, identification and avoidance of policy trade-offs)  Investment strategy (e.g. cost efficiency of choices, business cases)  Cross-agency collaboration (e.g. water and energy sectors, best societal outcomes)  Policy innovation (e.g. holistic approach to water and energy planning)  Public communication messages (e.g. more efficient use of resources)             

Water use within safe operating space - rate of surface and groundwater drawn from supplying catchments relative to the sustainable urban water allocation C Sustainable urban water allocation



Water pollutant load within safe operating space - point-source and diffuse nutrient

 

Policy innovation (e.g. industry innovation) Offset schemes (e.g. nutrient pricing) Setting pollution reduction targets Investment strategy (e.g. marrying innovation with best economic outcomes) Cross-agency collaboration Metrics to benchmark development performance (e.g. nutrient removal target) Investment strategy (e.g. business model, infrastructure prioritisation) Technological innovation (e.g. water treatment technologies) Metrics to benchmark water resource management performance (e.g. efficiency at different spatial scales) Policy planning and implementation (e.g. regulatory options, identification of trade-offs, decentralisation of water supply) Public communication messages (e.g. public acceptance recycled water) Water allocation for multiple water functions (e.g. environmental flows) Policy planning and implementation (e.g. regulatory options, land use planning and design) Metrics to benchmark development performance (e.g. urban runoff management)

Investment strategy (e.g. multifunctional spaces) Policy planning and implementation (e.g. regulatory options, better environmental outcomes)

23

Key objectives of urban water performance1

Restoration of natural hydrological flows (runoff, infiltration, Evapotranspiration)

Recognising the diverse functionality of water

Social Environmental Economic Urban spaces

Performance indicators and their quantification2 Currently achievable Aspirational loads discharged to surface and ground waters relative to sustainable discharge rates NWW + NSW Sustainable discharge rate Hydrological performance - post-urbanised (i) hydrological flows/fluxes relative to preurbanised flows/fluxes (o) Ri , Gi , ETi Ro Go ETo Supporting diverse functions - water needed to maintain desired functions relative to water budgeted for the functions W needed W allocated

Applicability of indicators in practice3 

Policy innovation (e.g. urban design)

 

Investment strategy (e.g. multifunctional spaces) Policy planning and implementation (e.g. regulatory options, better environmental outcomes) Policy innovation (e.g. urban design)



 Policy planning and implementation (e.g. urban design, land use development and control, multifunctional urban spaces)  Policy and technological innovation (e.g. blue infrastructure, alternative water supplies)  Cross-agency collaboration (e.g. planning for the whole catchment)  Investment strategy  Water allocation for multiple water functions (e.g. other purposes either than human consumption)  Offset schemes (e.g. water levy programs)  Metrics to benchmark development performance (e.g. landscape and open space design)

Notes: 1 Derived from the review of urban water management visions an d principles set by urban water industry bodies and international development agencies. See section 2.2 for definitions of these objectives. 2 Equations for quantifying the indicators using data generated from an urban water mass balance. See Figure 1 for acronym definitions. 3 Practice refers to stakeholder’s area of work and allocated responsibility within their organisation. 4Environmental water refers to water supplies that are drawn from the environment.

24

Appendix A Table A1: Visions and goals for urban water management Water Sensitive Cities (Wong et al. 2013; p.13)  Cities as water supply catchments: meaning access to a range of different water sources at diversity of supply scale;  Cities providing ecosystem services: meaning the built environment supplements and supports the functions of the natural environment; and  Cities comprising water sensitive communities: meaning socio-political capital for sustainability exists and citizen’s decisions and water behaviours are water sensitive

Water Wise Cities (IWA 2016) Regenerative water services:  Replenish water bodies and their ecosystems  Reduce the amount of water and energy used  Reuse, recover, recycle  Use a systematic approach integrated with other services  Increase the modularity of systems and ensure multiple options Water sensitive urban design:  Enable regenerative water services  Design urban spaces to reduce flood risk  Enhance liveability with visible water  Modify and adapt urban materials to minimise environmental impact Basin connected cities:  Plan to secure water resources and mitigate drought  Protect the quality of water resources  Prepare for extreme events Waterwise communities:  Empowered citizens  Professionals aware of water cobenefits  Transdisciplinary planning teams  Policy makers enabling water wise action  Leaders that engage and engender trust

OECD principles (OECD 2015; p.34) Finance: - Optimised water infrastructure management - Tariffs and taxes that reflect the benefits and costs of water security - Targeted subsidies only Innovation: - Smart and distributed water systems - Combining a variety of water sources - Green water infrastructure - Water-sensitive urban design Urban-rural interface: - Tradable water rights - Contracting for groundwater conservation - Land-use based flood management - Payments for water quality services Governance: - Metropolitan governance - Dedicated regulatory bodies for water supply and sanitation - Stakeholder engagement

Asian Water Development Outlook (ADB 2016) Household water security: - Universal access to safe and reliable water and sanitation services Economic water security: - Recognition of water’s support for economic activities, and of the water-food-energy-nexus Urban water security: - Creation of city-wide watersensitive infrastructure and management procedures - Sustained sources of public financing for water and environmental protection - Sustainable levels of public water consumption - Support for advanced water technology, and research and development - Robust international water partnerships Environmental water security: - Progress is made on restoring rivers and ecosystems to health on national and regional scales Resilience to water-related disasters: - Fostering of resilient, adaptable communities - The consequences of natural disasters are less severe

25

UK Water Partnerships (UK Water Partnership 2015) Five visions of the future relationship between cities and water: 1. Green food and garden cityscapes - More food is grown in cities, both in and on buildings - Water management systems encompass cities, catchments and underground geology, ensuring climateresilient food production and drainage. - The food and water footprints of new cities are equivalent to the farms or forests they are replacing 2. Flood-proof cities - Cities are designed to withstand sealevel rise, extreme rainfall and expansion of river floodplains - The benefits of flooding are recognised and harnessed whenever possible 3. Smart homes & city networks - Via the internet, water utilities communicate their needs, status, condition, etc. to data hubs, which manage water supply, demand, efficiency, and performance. 4. Cities & the underworld - Deep geology houses drainage, water, heating and cooling services - Reduced reliance on large surfacewater reservoirs 5. Community transition cities - Utility-run programmes improve the sustainability of community water habits

ACCEPTED MANUSCRIPT

Figure 1. Extended urban water mass balance Notes: Based

on an approach originally described by Kenway et al. (2011a) and further developed by Farooqui (2016). Blue arrows are natural hydrological flows, and yellow arrows are anthropogenic flows managed by urban water infrastructure.

ACCEPTED MANUSCRIPT Highlights There is a gap between the visions for urban water and performance assessment Objectives for urban water management were categorised from industry visions A set of indicators were derived for gauging performance against these objectives Indicators can be quantified using data from an urban water mass balance Other indicators are aspirational requiring further method development