Advancing water quality assessment under uncertainties: Multi-risk and multi-scenario analyses in the face of future climate change

Water quality is a critical element of ecosystem health and human well-being. However, it is increasingly challenged by a variety of human induced impacts related to land-use, socio-economic development, and climate change that alter the physical, chemical, and biological components. It is challenging to obtain a comprehensive understanding and effective management of water quality, especially under large uncertainties arising from future climate change and socio-economic developments. An integrated approach is essential for developing adaptive strategies that consider future uncertainties, ensuring the preservation of water quality and the sustainability of aquatic ecosystems in the face of evolving environmental conditions. This research investigates the intricate dynamics of water quality in transitional environments with a case study in the Venice Lagoon, particularly focusing on the uncertainties arising from future climate change. Utilizing a multi-scenario analysis approach, we explore a range of potential outcomes to understand the complex interactions shaping water quality in these critical ecosystems. The scenarios are designed to simulate future conditions, considering two different climate change scenarios (RCP 4.5 and RCP 8.5), river load (reduced/unvaried river runoff), and the operation of the marine hydraulic interventions for flood prevention (the MOSE system) under medium- and long-term futures. Using data from SHYFEM-BFM - a 3D coupled hydrodynamic and ecological model, key physico-chemical parameters are integrated into a multi-parameter water quality index the CCMEWQI. This index considers the Scope (number of failed parameters), Frequency, and Amplitude of non-compliant tests to water quality standards for ecological status and aquatic life. By exploring diverse trajectories, we aim to anticipate potential shifts in water quality spatio-temporal dynamics. The multi-scenario analysis unfolds potential future states of water quality in the Venice Lagoon, highlighting critical points of vulnerability and resilience.The outcomes contribute to a more comprehensive understanding of the complexities inherent in transitional water systems, aiding policymakers and water resource managers in making informed decisions to ensure the resilience and sustainability of water quality in the face of an uncertain future. Additionally, future developments extend the scope of this study to encompass a multi-risk assessment on river networks in the Veneto Regione to understand the multi-risk dynamic for regional water quality management. The multi-risk analysis in the freshwater system incorporates a range of stressors to river water quality, including single/compound extreme climate events and anthropogenic activities. We aim to unravel the multi-risk dynamics through the application of a novel approach employing machine learning techniques that encompass multiple hazards, exposures, and vulnerabilities. Furthermore, future scenarios of climate, land-use, and population changes are integrated into the multi-risk model together with nature-based solutions to create multi-risk scenarios for water quality, providing a holistic view of the potential risks and vulnerabilities in different environmental contexts.