Abstract
Freshwater lakes are increasingly affected by interacting ecological, infrastructural and socio-economic pressures, yet research on regulated deep lake systems has mainly focused on biophysical processes, with comparatively limited attention to how local stakeholders perceive ecological change and sustainability transitions. This study addresses this gap by examining how stakeholders interpret environmental change, water governance and future sustainability in Lake Idro, a regulated deep subalpine lake in northern Italy. The novelty of the paper lies in integrating limnological evidence with qualitative stakeholder perspectives to show how perceived ecological improvement, governance conflicts and institutional trust jointly shape local understandings of sustainability. The study combines documentary and scientific evidence with a focus group and semi-structured interviews with 21 stakeholders, including residents, institutional actors, environmental associations and tourism operators. Data were analyzed through an inductive approach inspired by the Gioia methodology. The findings identify two interrelated dimensions: Ecological Perception and Participatory Awareness, which captures how visible environmental changes and lived experience inform local interpretations of lake conditions; Territorial Governance and Local Development, which reflects concerns over water regulation, tourism, infrastructure and institutional legitimacy. Stakeholders generally perceive an improvement in the lake’s ecological and esthetic condition following reduced water-level fluctuations, while expressing concern that new hydraulic interventions could reintroduce ecological instability and undermine tourism-based development. By connecting ecological evidence with socially mediated perceptions of change, the study contributes to environmental management and adaptive water governance debates, highlighting the importance of knowledge exchange, participatory decision-making and institutional trust in managing regulated lake systems.