Exploring hydrological changes across a mountain basin in Friuli-Venezia Giulia through a distributed hydrological model

Climate change is one of the anthropogenic factors inducing alterations in hydrological processes, known as hydrological changes. To assess these changes at catchment scale and evaluate their impacts on the hydrology-related hazards, spatially-distributed and physically-based hydrological models represent reliable and suitable tools. However, significant challenges remain in achieving robust parameterization and calibration, mainly due to data limitations, spatial and temporal scale mismatches, and the intrinsic complexity of hydrological processes.

In this study we adopt the Triangulated Irregular Network-based real-time integrated basin simulator (tRIBS) hydrological model to build a proper laboratory tool enabling a comprehensive high-resolution distributed analysis on the response to scenarios of changes of multiple hydrological aspects, such as runoff components partitioning, evapotranspiration fluxes andsoil moisture dynamics. The case study is the Cedarchis basin, a part of the municipality of Arta Terme in the Friuli-Venezia Giulia (FVG) region, located in the north-eastern Italy. The basin covers 125 km², as part of the main Tagliamento river basin, and the Chiarsò stream flows through it. Stream flow is monitored through an ultrasonic stream gauge installed at the outlet and managed by the Civil Protection Department of the FVG region. Additional stream measurements are available along the Chiarsò stream due to a small private hydropower plant. Rainfall data are available for the Paularo station, located approximately at the center of the basin. The calibration was conducted using data from the 2023-2024 period, which includes the proper spin-up time. To update and enhance the rating curve, required to transform hydrometric readings into discharge, we carried out multiple field measurements of stream flow managed by the water resources management service (Servizio Gestione Risorse Idriche) of the region. This time series was subjected to procedures of corrections, such as filling, extrapolation and filtering, with two moving windows, to reduce instrumental noise. The Nash-Sutcliffe efficiency coefficient (NSE) was used to perform the calibration and validation. Finally, to evaluate the response of the basin to climate change, synthetic precipitation series generated using an advanced weather generator for the 2050 and 2100 horizons under the RCP 4.5 and RCP 8.5 scenarios are used.

This research received funding from European Union NextGenerationEU – National Recovery and Resilience Plan (PNRR), Mission 4, Component 2, Investiment 1.1 -PRIN 2022 – 2022ZC2522 - CUP G53D23001400006.