The presentation by Dr. Gustavo Fimbres, a researcher at the University of Sydney, on "Circular Economy and Case Studies in Australia," offered a modern and complementary perspective to the previous presentations on ancestral practices. Fimbres began by explaining the fundamental principles of the circular economy, emphasizing the importance of designing processes and products to minimize waste generation from the outset. He highlighted how these principles can be applied to the water cycle, a central theme in discussions about Nezahualcóyotl and Tezcotzingo. The expert detailed how the circular economy of water involves the recovery and valorization of materials contained in wastewater. He explained that these materials can be transformed into fertilizers, minerals, or food supplements, thereby creating a closed loop of resources. Fimbres presented several case studies from Australia, focusing on pilot projects in Sydney. He described how Sydney Water is implementing water recirculation systems, where wastewater is treated to drinking water standards and reintegrated into the supply system indirectly. An interesting aspect of his presentation was the discussion on the social and psychological challenges associated with water reuse. Fimbres explained how these pilot projects are addressing public concerns and demonstrating the safety and effectiveness of these practices. The researcher also discussed projects involving greywater recycling at the household level and the recovery of energy from gases generated in wastewater treatment plants. He emphasized how these approaches not only conserve water but also recover nutrients and energy, exemplifying the principles of the circular economy. Fimbres concluded his talk by reflecting on how these modern approaches align with the principles of sustainable water management observed in the ancestral practices discussed earlier in the webinar. He underscored the importance of combining traditional knowledge with technological innovation to address current sustainability challenges. This presentation not only provided concrete examples of modern sustainable practices but also bridged the gap between ancestral knowledge and contemporary solutions. Fimbres' talk reinforced the webinar's central idea: that lessons from the past, combined with current innovation, can offer powerful solutions to the sustainability challenges we face globally.