Water is becoming an increasingly challenging issue for city managers around the world, in both developing and developed countries. Many of the world’s largest urban areas are located in water-stressed areas, making it difficult to provide good quality water services to ever-increasing populations. Climate change is further amplifying the pressure, increasing the frequency and severity of droughts, floods, sea level rise and other phenomena that endanger water resources. With two-thirds of the global population predicted to be living in cities by 2050, there is a growing urgency for cities to invest in optimizing their water systems to respond to the challenges of the 21st century.

These challenges, as threatening as they may seem, can be overcome. Through careful planning, effective governance and the adoption of the right technologies, urban systems can be optimized to provide abundant and affordable water for all users, both now and in the future.

In order to measure the state of water optimization around the world, Economist Impact has developed a city water optimization index, sponsored by DuPont Water Solutions. It consists of 47 quantitative and qualitative indicators that assess the extent to which cities have the necessary policies, infrastructure and systems in place to optimize their water services.

The three general categories of indicators are: reliability, accessibility and sustainability. Category scores are calculated from the weighted average of the indicators and scored from 0 to 100, where 100 is the most favorable score. The overall index score is calculated from a simple weighted average of the three category scores.

Reliability means a supply system that guarantees sufficient water today and in the future, through resilient sources, water quality and effective management and coordination. The reliability category focuses on how cities effectively use water, the standards and protocols they apply to ensure water quality, and their level of strategic and long-term planning and foresight, supported by the right forms of collaboration. and coordination with key stakeholders. Reliability subcategories, indicators and sub-indicators are:

1 Sources of water

1.1 Macro measurement of water

1.2 Protection of water sources

1.3 Diversification of water sources

1.4 Unconventional water sources

2 Water quality

2.1 Treatment to comply with water quality guidelines

2.2 Water quality standards

2.3 Water surveillance

3 Management and coordination

3.1 Long-term plan and strategy

3.2 Collaboration and coordination (3.2a Institutional coordination within the city; 3.2b Upstream and downstream coordination)

3.3 Risk analysis and climate modeling

3.4 Independent supervision

Affordability means that end-users have access to safe and affordable water and sanitation services, which implies sufficient levels of water and sanitation connectivity, equitable water pricing and safety procedures to minimize risks of disruption, including risk mapping and mitigation, early warning systems, and monitoring and public awareness of urban risks. Accessibility subcategories, indicators and sub-indicators are:

1 Water connectivity

1.1 Residential accessibility

1.2 Non-residential accessibility

2 Sanitation

2.1 Wastewater system coverage

2.2 Wastewater treatment

3 Equitable water prices

3.1 Cost coverage

3.2 Equity

4 Risk mitigation

4.1 Risk reduction strategy

4.2 Risk maps

4.3 Early warning systems

4.4 Public awareness

5 Management and coordination

5.1 Data analysis

5.2 Monitoring and evaluation of infrastructures

5.3 Improvement and maintenance of infrastructure

Sustainability assesses the extent to which waste is minimised, efficiency is maximized and water quality is adapted for different types of use. Includes innovations such as smart metering and recovery of nutrients and energy, pricing policies to encourage conservation, levels of water recovery and improved public perception of water reuse, as well as the inclusion of building water systems with building regulations and ecosystem protection. Reliability subcategories, indicators and sub-indicators are:

1 Waste reduction

1.1 Technology monitoring (1.1a Smart meters; 1.1b Real-time monitoring system; 1.1c Use of artificial intelligence and machine learning)

1.2 Nutrient and energy recovery (1.2a Wastewater sludge; 1.2b Energy recovery; 1.2c Nutrient recovery)

2 Efficiency

2.1 Continuity of water services

2.2 Unbilled water

3 Water conservation

3.1 Building codes

3.2 Prices that encourage conservation

3.3 Education for water conservation

4 Reused water

4.1 Legislation on reused water

4.2 Financial incentives for water reuse

4.3 Decentralization of distribution and treatment (4.3a Decentralization of distribution; 4.3b Decentralization of treatment)

4.4 Reused water distribution systems (4.4a Mandate for reusing water; 4.4b Reused water network)

4.5 Public perception of reused water

5 Management and coordination

5.1 Collaboration in transforming waste into resources

5.2 Environmental protection

5.3 Water sensitive design principles

5.4 Protection of critical aquatic habitats and the ecosystem

In summary, the objective of this proposed index is to contribute to all users having access to safe, accessible and reliable water, both now and in the future, being a valuable tool for policy makers to assess how well their city is equipped to achieve these goals and learn from their peers in areas of innovation, enabling better-targeted investments for a sustainable future for all.

This index was applied to fifty cities around the world. The results of the first edition are encouraging and show the city of Lisbon in a very pleasant fourth position, with a good balance between accessibility, resilience and sustainability. Indeed, it appears to lead the European region. The continued work carried out by EPAL and the recent effort by Lisbon City Council towards the evolution towards a greener city certainly contributed to this.

From this analysis, the main conclusions are that: the city of Los Angeles obtained the highest global score, closely followed by Melbourne; reliability and accessibility were the two categories in which cities performed best, but sustainability scored the lowest; low- and middle-income cities are often among the top performers in at least one of the key categories; most cities can consistently provide good quality drinking water to their inhabitants; cities are recognizing the need for better water monitoring; many cities suffer from water scarcity, making achieving water sustainability all the more pertinent; cities’ ability to improve their sustainability scores depends on better policies; cities need to think of water management as a circular process rather than a linear relationship between supply and demand.

Text extracted and adapted from the publication “The 2021 City Water Optimization Index: Achieving reliable, accessible and sustainable urban water systems through innovation and collaboration”, which you can consult at:

https://impact.economist.com/sustainability/project/ water-optimisation/download/EconomistImpact-CityWaterOptimisationIndex-Nov-2021.pdf