Water Efficiency in Cities - indexes, benchmarks and metrics

Efficient urban water management is essential to meet the challenges of climate change and population growth. By 2050, 86% of the population of OECD countries will be living in cities (OECD, 2014). Water efficiency and water conservation is an integral part of this. There have been several recent indexes produced of sustainable cities focussing on water management. In this blog post I outline the results in relation to water efficiency and how we might be able to improve indicators in this area. The International Water Association Efficient Urban Water Management Specialist Group is also currently assessing examples of best practice and new indicators to benchmark cities and utilities.

Sustainable Cities Water Index 2016

Released in May 2016 the Sustainable Cities Water Index was produced by Arcadis and the Centre for Economics and Business Research. A sub-index was produced for efficiency and this is illustrated below. The index focusses on efficiency and controlled management of water and is built up from seven indicators. In this study Copenhagen ranks highest linked to one of the lowest rates of leakage, relatively high unit charges for water and a high proportion of metered supplies.

Of interest from my perspective being based in London is the relatively low score for UK cities of Manchester, Birmingham and London. These low scores are linked to low levels of water reuse and water metering.

Sustainable Cities Water Efficiency sub-index 2016

The table below outlines the indicators used in the efficiency sub-index and the sources of data behind them. A weighting is applied to the indicators also in calculating the total scores for cities.

City Blueprint Framework and Blue Cities Index 2015

An EU initiative has been developing a City Blueprint Framework, which was initially applied to 11 cities in 2013 and expanded in a Horizon 2020 project to cover 45 municipalities and regions internationally in 2015. This framework recognises the unique nature of the social, financial and environmental setting of each city and applied this in the choice of indicator. An example give is that limited natural water availability in semi(arid) regions may result in a low score for water stress while the city may be a frontrunner in water efficiency practices. Measuring urban performance to reduce water consumption is outlined as a fairer comparison between cities.

The following indicators relate to water efficiency directly (see paper assessing these):
  • Infrastructure - water system leakage (based on percentage leakage)
  • Climate robustness - drinking water consumption (total consumption for a city m3)
  • Governance - water efficiency measures
A map of the Blue Cities Index results is provided below. This shows the highest scores in Europe, medium scores in the UK, Australia and North America and lower scores in developing/ transition economies. 

Blue Cities Index 2015 (Koop and Van Leeuwen)

Further details on specific indicators and scores for cities are available in several reports online. The average water efficiency score in the latest assessment was 7.9 on a scale from 0 to 10. Water efficiency is core to the narratives around rankings for blue cities. For example, a score of 4-6 is a water efficient city, 6-8 a resource efficient and adaptive city, and 8-10 a water wise city. No city has achieved water wise city status to date and London is ranked as a resource efficient and adaptive city with a score of 7.1. Leakage rates varied from 2% in Berlin to 60% in Varna with an average of 21%

Water Sensitive Cities Index 2016

The Water Sensitive Cities Index is another approach currently in development and that has been trialled with several cities in Australia and Asia. The index is designed to:
  • Benchmark and rank cities based on water sensitivity performance
  • Set targets and track progress
  • Inform management responses to improve water sensitive practices, to enable the transition to a water sensitive city
  • Forster industry collaboration

A demonstration portal is currently live (image and link below). This includes several Australian cities and others in the region. The demonstration scores currently rank Australian cities as Brisbane, Sydney, Melbourne, then Perth for being water sensitive.

Melbourne Project Demonstration of the Water Sensitive Cities Index 

The indicators behind the assessment are included in the table below. Of these water efficiency relates to many of the broader governance indicators. More specific indicators for water efficiency include, low end user potable water demand, low GHG emission in water sector, diversified self sufficient fit-for-purpose water supply, and integration and intelligent control. 

Example indicators for Water Sensitive Cities Index (Chesterfield, 2015)

Alliance for Water Efficiency State Scorecard 2012

In 2011 the US Alliance for Water Efficiency surveyed 50 states to identify and assess water conservation laws and policies. The survey included 20 questions and each was scored qualitatively for the state. These ranged from 1 point for answering if there is a state agency in charge of drinking water conservation to 3 points for robust water loss regulation and policy with targets across all suppliers.

Scores were then translated into a grading scale of A to D with A+ being the highest score and D the lowest. The results are mapped below and this study usefully outlined the variation in policy across the country. A detailed policy analysis is also included in the report along with a follow-up report based on public comments and dialogue generated by the results.
Assessment of water conservation policies USA 2012

Water Conservation Measurement Metrics 2009

In 2009 the American Water Works Association funded a study to provide guidance on standardised methods of calculating metrics and to outline the advantages and disadvantages of these. The study utilised data from seven US water utilities to illustrate the appropriate use of metrics. Some of the key data and metrics that may be used within wider benchmarks and indexes are outlined. In particular the authors provide a detailed assessment of the advantages and disadvantages of metrics of aggregate water use such as per capita production, sector specific water use, annual and seasonal water use. 

Due to the variation in environmental and social factors experience by different utilities it was suggested that only ratio based indicators similar to the IWA infrastructure leakage index (ILI) would be appropriate. An indoor conservation index (ICI) formula is proposed based on the ratio of current intensity and presence of end uses. A total of 23 metrics of water use and conservation are presented and discussed.

Indicators for Water Efficiency

Based on the elements of water efficiency within the indexes above it is clear that there is a wide variation in current performance and the opportunity for many cities to improve. This supports the need for a higher resolution analysis of water efficiency specifically for cities, utilities and states/ countries. An assessment of this type could also support discussions on best practice, knowledge sharing and provide potential approaches to transition from low levels of water efficiency to higher levels of water efficiency. This is particularly important from a resilience perspective to address the pressures from climate change and population growth. Also, a joint qualitative and quantitative approach may be needed for this area.

A water efficiency index could include indicators such as:
  • Leakage - using indicators such as the Infrastructure Leakage Index
  • Water efficient behaviours
  • Smart metering
  • Carbon emissions from water use
The IWA Efficient Urban Water Management specialist group has identified the need to collate evidence on water efficiency projects to support such an index. Although there have been several decades of progress in this area there are few collations of this evidence, excluding the Waterwise evidence base in the UK and the Water Resources Group 2030 managing water scarcity catalogue.

Sustainable and integrated water management

Many of the index approaches are moving towards an integrated view of water management. However, the direct links between different indicators aren't often made and there is the potential for less sustainable outcomes where desalination and water reuse capacity score highly but may have a higher carbon emission potential than other options. Indexes are useful for providing a comparison between cities and starting dialogue, however more detailed approaches are needed to consider social, environmental and economic trade-offs. One way of looking at this is in terms of resilient pathways:

"Resilient pathways will simultaneously reduce GHG emissions, lower overall water demand, maintain overall environmental quality and allow living standards to continue to improve"

Water efficiency measures can deliver benefits for adapting to climate change but also mitigation benefits, especially when considering emissions from heating hot water. As we integrate water management we need to ensure that the evidence and knowledge base on water efficiency is taken forward also.


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