Characterizing an Artificial Wetland through Hydrologic and Isotopic Monitoring

Wetlands are critical ecosystems essential to human and environmental health, delivering diverse ecosystem services such as food security, biodiversity preservation, climate change mitigation, water filtration, aquifer feeding, and regulation. When present, wetlands play a vital role in catchment drainage systems, providing water storage, flow regulation, infiltration, and chemical processing. Despite their ecological significance, wetlands have been decreasing in number and extent globally. However, the construction of artificial wetlands has steadily increased in recent decades due to recognition of their eco-hydrological importance and benefits. Wetlands are widely acknowledged as an effective nature-based solution. The ecological status of wetlands and the performance of their ecosystem services are closely tied to the hydroperiod. A wetland's hydroperiod is determined by the interplay of water inflows and outflows, the geomorphology of the catchment, and subsurface properties. Understanding and managing the hydroperiod of artificial wetlands is vital to maintaining and increasing ecological and hydrological integrity. Hence, artificial wetlands must be assessed based on both their internal functional processes and their hydrological interactions with the surrounding environment, including water exchanges, sediment transport, and nutrient dynamics.

This study analyzes an artificial wetland in the Tuscany, Central Italy, known as Oasi di Gabbianello. Built in 2004, it has become an important ecological site, offering resources and habitat to various plant and animal species, especially migratory birds. The study objectives were to: i) characterize the hydroperiod and its key drivers; ii) develop both a conceptual and numerical hydrological model; and iii) validate the models using hydrometeorological and stable isotope data. These models are essential for enhancing the resilience of the wetland to future climatic stresses. 

A monitoring program was implemented, including continuous measurements of meteorological conditions, water inflow and outflow, and wetland water levels, alongside biweekly sampling for stable isotope analysis over one year. Continuous monitoring enabled a hydroperiod characterization, revealing precipitation and stream inflow as primary water gains, while evaporation and overflow constituted major losses. Seepage was undetectable at the resolution of observation. Both conceptual and numerical models accurately represented water volume variations, while stable isotope data highlighted transitions between recharge- and evaporation-dominated periods, providing an additional dataset for model validation.

Keywords: Wetland; Hydrology; Water Isotopes; Modelling.