Table 1 Different levels of sustainable IWRM in cities worldwide

0–2

Cities lacking basic water services

Access to potable drinking water of sufficient quality and access to sanitation facilities are insufficient. Typically, water pollution is high due to a lack of wastewater treatment (WWT). Solid waste production is relatively low but is only partially collected and, if collected, almost exclusively put in landfills. Water consumption is low, but water system leakages are high due to serious infrastructure investment deficits. Basic water services cannot be expanded or improved due to rapid urbanisation. Improvements are hindered due to governance capacity and funding gaps.

2–4

Wasteful cities

Basic water services are largely met, but flood risk can be high and WWT is poorly covered. Often, only primary and a small portion of secondary WWT is applied, leading to large scale pollution. Water consumption and infrastructure leakages are high due to the lack of environmental awareness and infrastructure maintenance. Solid waste production is high, and waste is almost completely dumped in landfills. Governance is reactive and community involvement is low.

4–6

Water-efficient cities

Cities implementing centralised, well-known, technological solutions to increase water efficiency and to control pollution. Secondary WWT coverage is high and the share of tertiary WWT is rising. Water-efficient technologies are partially applied, infrastructure leakages are substantially reduced, but water consumption is still high. Energy recovery from WWT is relatively high while nutrient recovery is limited. Both solid waste recycling and energy recovery are partially applied. These cities are often vulnerable to climate change, e.g., urban heating and drainage flooding, due to poor adaptation strategies, stormwater separation and limited green surface ratios. Governance and community involvement has improved.

6–8

Resource efficient and adaptive cities

WWT techniques to recover energy and nutrients are often applied. Solid waste recycling and energy recovery are largely covered whereas solid waste production has not yet been reduced. Water efficient techniques are widely applied and water consumption has been reduced. Climate adaptation in urban planning is applied e.g., incorporation of green infrastructures and stormwater separation. Integrative, (de)centralised and long-term planning, community involvement, and sustainability initiatives are established to cope with limited resources and climate change.

8–10

Water-wise cities

There is no city scored within this category so far. These cities apply full resource and energy recovery in their WWT and solid waste treatment, fully integrate water planning and urban planning, have multi-functional and adaptive infrastructures, and local communities promote sustainable integrated decision-making and behaviour. Cities are largely water self-sufficient, attractive, innovative and circular by applying multiple (de)centralised solutions.