Southwest Europe (Spain, France, and Portugal) faces increasing human pressure on its freshwater resources, leading to scarcity, quality issues, usage conflicts, and environmental risks. The TARGET project aims to counter this by promoting territorial planning strategies that incorporate Non-Conventional Water (NCW) sources. This research delves into public and expert perceptions of NCW through a series of in-depth interviews. The study conducted 40 semi-structured interviews with experts and 60 with laypeople across the three countries. Each interview lasted approximately 25 minutes. Questions covered various aspects of NCW, including definitions, known types, their "lifecycle" and potential for reuse, typical uses and functions, and perceived differences between NCW sources. A key finding is the significant knowledge gap between experts and laypeople regarding NCW. This disparity highlights a critical need for improved communication strategies. The research suggests several recommendations for developing effective communication plans. These strategies should focus on providing general information about the use and implications of reused water, especially in the context of climate change adaptation. Bridging this knowledge gap is crucial for successful integration of NCW into regional water management, ultimately contributing to more sustainable water resource planning in Southwest Europe.