Resilience is the ability of individuals, communities, institutions, businesses, and systems to survive, adapt, and thrive in the face of stress and shocks, and even to transform when conditions require it. Three capabilities characterize a resilient system: persistence, adaptability, and transformability. Resilience should be integrated into all projects to prepare utilities, cities and governments for uncertain shocks and stressors (climate and non-climatic, such as changes in demand, land use, extreme weather events, demographics, and pandemics) in order to avoid the undesired impacts of a disruption or failure of water services.

Infrastructure already in place is a valuable resource. However, existing infrastructure is often not used to its fullest potential. Rather than building new infrastructure, existing or damaged infrastructure can be rehabilitated to function as it did in its original design. Existing infrastructure can be retrofitted or optimized to increase treatment capacity, provide additional services, or maximize service delivery at a fraction of the cost of new infrastructure. Exploiting the full potential of existing infrastructure also means connecting all households originally included in its design

Diversifying and protecting water supply sources support utilities and help cities hedge against risks. Utilities and cities must build diversified and dynamic water resources portfolios, making sure to protect and explore the use of all available water sources—including surface and groundwater, rainwater, treated wastewater, and seawater—and, whenever possible, to use fit-for-purpose approaches to minimize treatment costs. Ideally, to ensure resilience and flexibility of systems, the diversified water portfolio should include sources having different risk and cost profiles (for example, combining surface and groundwater), sources that respond to stress at different time scales, and, if possible, sources that have low vulnerability to shocks and stresses, such as desalination and treated wastewater. Actions must be planned and implemented using a systems approach. Specifically, interactions should be considered at the basin level because cities are part of catchments. As part of their water security strategy, cities and water utilities should become the stewards of their upstream and downstream watersheds, whether through catchment management, stakeholder engagement, strong political buy-in, or other means.

Resources can be recovered over the entire water cycle. Understanding the flow of resources in and out of their systems allows water supply and sanitation operators to identify opportunities to recover resources that are being underutilized or wasted at every phase of the water cycle. Ideally, a circular system is designed in a way that no resources are wasted. The recovered resources can provide an additional revenue stream for the utility or reduce operations and maintenance costs, making the utility more financially and environmentally sustainable. Resource recovery can be done at different scales and may include centralized and decentralized solutions. The right solution depends on the context.

Key to circular economy are operations optimized for efficiency, reliability, and performance. Poorly operated utilities jeopardize the sustainability of any other WICER solutions that may be deployed.

Managing, recharging, and preserving aquifers properly is crucial for long-term water security and resilience because groundwater is more likely to be compatible with a variable and changing climate. Aquifers can store large volumes of water. They also react more slowly to changes in rainfall and temperature than does surface water. If managed well, aquifers can be resilient buffers during long periods of water stress. To manage aquifers correctly, utilities need to monitor their water levels; regulate and set limits on extraction rates; and ensure that aquifers are not polluted.

A circular and resilient water sector not only minimizes waste and negative environmental impacts, but also actively restores precious natural systems, recognizing their economic value and their importance for a sustainable future. The value of water resources is fully recognized, and watersheds are carefully managed, preserved and restored.

Mainstreaming nature into infrastructure systems can lower investment costs and contribute to more sustainable and resilient water systems while protecting ecosystems and mitigating climate change. Nature-based solutions can meet the infrastructure investment gap in a cost-effective manner while benefiting local communities and the environment. For that reason, it is crucial to assess and analyze their potential (upstream and downstream) when preparing new projects.