The World Youth Day (WYD) is a worldwide encounter with the Pope celebrated about every three years in a different country. The most recent World Youth Day was celebrated in Lisbon, Portugal from August 1-6, 2023. Over one million pilgrims participated in this event. The main event took place next to the Parque Tejo, in a new green area in the city – a 38 ha park on a landfill site decommissioned in the 1990s.

This park was irrigated with reclaimed water, and the site added as a pilot for testing BWS tools, namely the environment for decision support and alternative course selection tool, the water-energy phosphorous balance planning module and the risk assessment for urban water reuse module. The integrated use of these BWS tools is being applied to support urban management in making smart and climate-resilient water decisions for an efficient water-energy-nutrient balance in Lisbon.