Cryosphere and lithology influence the hydrological gradients of high elevation Alpine catchments

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In high-elevation systems influenced by receding cryosphere, geomorphology and lithology can strongly influence the hydrology of river networks. During summer 2022–2023, we studied the water temperature, δ 18 O, pH, major ions, and trace element concentrations at two headwater catchments in the Eastern Italian Alps. We investigated the main streams at the spring and below the confluences with tributaries from glaciers, intact and relict rock glaciers, young moraines, and till deposits. In the non-glacierized catchment (6.3 km 2 ), water temperature increased from 1.6 °C at the intact rock glacier spring to 7.3 ± 1.5 °C at the catchment outlet, despite the inputs from till and rock glacier springs with <3.0 °C waters. In the glacierized catchment (3.7 km 2 ), the proglacial reaches had a water temperature of 6.9 ± 2.6 °C and the inputs from cold rock glacier springs decreased the water temperatures by 2–4 °C along the stream. Due to predisposing lithology, at the glacierized catchment the concentrations of trace elements such as Ni, Al, Mn, Zn, Y, and Li were high along the entire river network except in till and the relict rock glacier springs, which are not influenced by the cryosphere. For both catchment outlets, end-member mixing models estimated 60–65 % contribution from rock glaciers to stream runoff. In both river systems, meltwater from snow and ice was the dominant runoff component, with rainwater accounting for 20–30 % of runoff in the non-glacierized catchment and for <10 % in the glacierized one.