Effects of snowmelt on the runoff dynamics in two catchments with different forest stands

The forest stand can significantly affect the snow deposition and consequently the runoff during the melt period. This study focuses on water and element fluxes from snowpack in two Czech boreal headwater lake catchments with different forest stands (mature vs. regenerating after bark beetle tree dieback) using isotopic and hydrochemical tools. Sampling and analysis of the surface water, precipitation and snowpack throughout one  hydrological year enabled us to estimate the isotopic balance and chemical snowpack evolution, but also the snowmelt contribution in lakes inlets and outlets.

Isotopic signatures of the snowpack were seasonal, with δ²H amplitudes of -25‰ in the mature and -17‰ in the regenerating forest catchments. The mature forest had a ~1 month longer duration of snow cover and higher concentration of solutes in the precipitation and snowpack. In both catchments, heavier isotopes (¹⁸O and ²H) preferentially left the snowpack, which was saturated with rainwater. This resulted in the final spring snowmelt being enriched with lighter isotopes (¹⁶O and ¹H). Ions were also eluted from the snowpack during rain-on-snow events and partial snow melting throughout the winter, causing fluxes of diluted water at the end of the snowmelt. Our results demonstrate the hydrological and hydrochemical variability of the snowpack, which in the future may even increase with rising temperatures and changes of precipitation patterns.