Evaluation of hydro-climatic data and snow drought propagation in italian mountain catchments

Mountain regions are critical sources of freshwater for drinking water, irrigation, and hydropower; their hydrology is shaped not only by orographic precipitation, but also by the seasonal storage and delayed release of water by snowpacks. When precipitation or temperature anomalies persist, the resulting changes in snow storage can propagate into warm-season streamflow deficits, depending on the catchment's snow influence. Tracing this chain requires reliable estimates of meteorological forcing, snow water equivalent (SWE), and streamflow; yet sparse networks and complex topography limit direct observation of forcing and especially of snow storage, while streamflow records are often too short or disturbed for multi-decadal analyses. Hydrological assessment therefore depends on reconstructed datasets whose reliability requires careful evaluation. This research addresses these challenges across a set of Italian Alpine and Apennine catchments of contrasting snow influence through four interconnected analyses. First, it evaluates gridded meteorological products of different types as atmospheric forcing for rainfall-runoff modelling, combining direct comparison against an observational reference with indirect validation through streamflow simulation, judging each product by how closely its simulated streamflow matches observations. Second, it evaluates SWE estimates from three large-scale land-surface reanalysis products against a high-resolution national reference, relating their performance to biases in the meteorological forcing. Third, it parameterises two structurally distinct conceptual models with a multi-objective calibration against both streamflow and SWE, testing whether snow observations constrain snow-process parameters more effectively than streamflow alone. Fourth, it identifies streamflow drought events in the resulting simulations and classifies them by dominant generating process, using a drought typology adapted for snow-influenced catchments. Overall, the work provides a transferable approach for assessing hydro-climatic data reliability in mountain environments, a multi-objective calibration framework for physically consistent streamflow and SWE series, and process-based insights into how precipitation, temperature, and snow-storage anomalies generate streamflow drought.