Runoff response to rainfall events considering initial soil moisture – Analysis of 9-year records in a small Alpine catchment (Brixenbach valley, Tyrol, Austria)

Abstract

Study region: Brixenbach catchment (10 km²), Kitzbuehel Alps, Tyrol, Austria. Study focus: This study presents the data of one of the rare soil moisture networks in the Alps, a 9-year soil moisture time series recorded at 8 sites with in-situ measurements (six pasture and two forest sites). We aim at understanding the soil moisture behaviour in general, its reaction to rainfall considering the site characteristics and the runoff reaction depending on the antecedent soil moisture content. We analysed soil moisture, rainfall and discharge data with a temporal resolution of one hour (summer months) and two hours (autumn to spring) respectively and interpreted the results in terms of land use and topographical features. New hydrological insights for the region: The medians of the soil moisture positively correlate with the sites’ altitude. Comparing spatial standard deviation of soil moisture versus spatial mean shows a high scatter of the standard deviations, contrary to previous studies, which use considerably shorter time series. The spatial variability increases with spatial mean, thus the highest spatial variability is recorded at wet conditions. The catchment shows clear threshold behaviour: Runoff coefficients above 0.23 only occurred when the soil moisture spatial mean of the eight sites overrun 43.5 vol% which can be translated into a saturation deficit of 0.28.

Keywords

• Soil moisture
• In-situ measurements
• Land use
• Runoff threshold
• Soil moisture monitoring