Hydrogeochemical and isotopic monitoring strategies for water resource sustainability: the Pordenone Plain (NE Italy)

This study investigates the seasonal hydrogeochemical dynamics of the Pordenone Plain hydrogeological system (NE Italy). Despite abundant water resources, the system faces increasing anthropogenic and climatic stress. A hydrogeochemical conceptual model was previously developed for this setting. Building on this foundation, the present study examines the processes governing seasonal groundwater dynamics, recharge variability, and the system's response to extreme hydroclimatic events. The results reveal marked seasonal variations among aquifers, reflecting hydro-lithological differences and providing a baseline for assessing aquifer resilience to future climate-driven recharge changes. The complex and heterogeneous intermediate flow system comprises two main flow paths. The first feeds foothill karst springs, responding rapidly to pre-Alpine/Alpine precipitation and snowmelt but experiencing reduced discharge during dry periods. The second flow path recharges the alluvial plain aquifers. High and Low Plain aquifers contrast, separated by the resurgence belt, a marked permeability transition. High Plain aquifers exhibit seasonal variations closely linked to piezometric fluctuations, whereas Low Plain aquifers display an inverted seasonal pattern. This inversion reflects the permeability contrast along the resurgence belt, which is inferred to decrease groundwater flow velocities and induce a "delayed seasonal recharge response". Conversely, the deep flow system remains unaffected by surface variations, indicating that deep confined aquifers are effectively decoupled from shallow hydrogeological dynamics. This integrated geochemical and isotopic approach enables the characterization of aquifer vulnerability and seasonal recharge dynamics. When integrated with quantitative hydrological assessments, these findings support the development of comprehensive management strategies to prevent water quality degradation and promote long-term groundwater sustainability.