Isotopic characterization of snow variability in two mountainous catchments, black forest mountains, Germany

Intense snow sampling was carried out during 2003 and 2004 in two meso-scale catchments (Dreisam catchment, 257 km², and Bergsee catchment, 11 km²) located in the southern Black Forest Mountains in Germany. The objective of the study was to describe the spatial variability of snow cover, snow water equivalent and isotope concentrations of deuterium (²H) and oxygen-18 (¹⁸O) in ⁰/₀₀ vs. VSMOW. Snow samples were collected with integral augers and characterized by geographical location, altitude, snow depths and snow characteristics. The results indicate a clear correlation of snow depth and water equivalent with altitude and a rather weak correlation of isotope concentrations to altitude. The isotope concentrations of 65 snow samples collected in 2003 varied between -10.2⁰/₀₀ and -14.9⁰/₀₀ for δ¹⁸O, -60⁰/₀₀ and -109⁰/₀₀ for δ²H and between 10⁰/₀₀ and 25⁰/₀₀ for the deuterium excess (DE). In 2004 the variations of 64 samples were between -7.7⁰/₀₀ and -13.1⁰/₀₀, -43⁰/₀₀ and -87⁰/₀₀ and 4⁰/₀₀ and 28⁰/₀₀, for δ¹⁸O, δ²H and DE respectively. A spatial variability could be described for both catchments. The influence of evaporation of some samples on lower altitudes could be identified using deuterium excess calculations. Our study lead to a better description of isotope variations in snow cover of mountainous catchments and might therefore be useful to enhance tracer aided hydrological modeling approaches which often only refer to precipitation input concentrations of single observation points in monthly resolution.