3.2.1 Artifical tracers
Artificial tracers were applied to infer the connection between glacier
input from the meltwater stream and the rock glacier spring. Tracer
injection was downstream of the cirque glaciers where the glacier melt
water infiltrates into the sediments in the vicinity of the rooting zone
of the rock glacier (which is already disconnected from the cirque
glaciers; Figure 1b). Two tracer experiments were performed with
injection points along the creek that infiltrates into the rooting zone
of the rock glacier in two different years (Figure 1b; 2015: distance to
the gauging station ~980 m; 2017: distance to the
gauging station ~910 m) using fluorescein as a
conservative dye tracer. In 2015 25 g of tracer were injected, in 2017 a
greater amount of 202,5 g was used. Detection of tracer concentrations
was done using a field fluorometer GGUN-FL30 (Abilla Co.; Schnegg, 2002)
installed at the gauging station. Linear flow velocities were calculated
based on the observed peak tracer concentration as well as on the mean
tracer residence time using the method of moments (Kreft & Zuber,
1978).