We analyse water balance, hydrological response, runoff and snow cover characteristics in the Jalovecký Creek catchment (area 22 km2, mean elevation 1500 m a.s.l.), Slovakia, in hydrological years 1989–2018 to search for changes in hydrological cycle of a mountain catchment representing hydrology of the highest part of the Western Carpathians. Daily air temperature data from two meteorological stations located in the studied mountain range (the Tatra Mountains) at higher elevations show that the study period is 0.1°C to 2.4°C warmer than the climatic standard period 1951–1980. Precipitation and snow depth data from the same stations do not allow to conclude if the study period is wetter/drier or has a decreasing snow cover. Clear trends or abrupt changes in the analysed multivariate hydrometric data time series are not obvious and the oscillations found in catchment runoff are not coherent to those found in catchment precipitation and air temperature. Several time series (flashiness index, number of flow reversals, annual and seasonal discharge maxima, runoff coefficients) indicate that hydrological cycle is more dynamic in the last years of the study period and more precipitation runs off since 2014. The snow cover characteristics and climatic conditions during the snow accumulation and melting period do not indicate pronounced changes (except the number of days with snowfall at the Kasprowy Wierch station since 2011). However, some data series (e.g. flow characteristics in March and June, annual versus summer runoff coefficients since 2014) suggest the changes in the cold period of the year.
δ18O in precipitation at station Liptovský Mikuláš (about 8.5 km south from the outlet of the Jalovecký Creek catchment) remains constantly higher since 2014 that might be related to greater evaporation in the region of origin of the air masses bringing precipitation to the studied part of central Europe. Increased δ18O values are reflected also in the Jalovecký Creek catchment runoff. Seasonality of δ18O in the Jalovecký Creek became less pronounced since 2014. The most significant trends found in annual hydrological data series from the catchment in the study period 1989–2018 have the correlation coefficients 0.4 to 0.7. These trends are found in the number of flow reversals (change from increasing to decreasing discharge and vice versa), June low flow, number of simple runoff events in summer months (June to September) and the flashiness index. The attribution analysis suggests that drivers responsible for the changes in these data series include the number of periods with precipitation six and more days long, total precipitation amount in February to June, number of days with precipitation in June to September and total precipitation in May on days with daily totals 10 mm and more, respectively. The coefficients of determination show that linear regressions between the drivers and supposedly changed data series explain only about 31% to 36% of the variability. Most of the change points detected in the time series by the Wild Binary Segmentation method occur in the second and third decades of the study period. Both hydrometric and isotopic data indicate that hydrological cycle in the catchment after 2014 became different than before.
The role of stony soils in runoff response of mountain catchments is rarely studied. We have compared simulated response of stony soils with measured catchment runoff for events caused by rains of small and high intensities in the mountain catchment of the Jalovecký Creek, Slovakia. The soil water response was simulated for three sites with stoniness 10–65% using the Hydrus-2D single porosity model. Soil hydraulic parameters employed in the modelling, i. e. the saturated hydraulic conductivity and parameters of the soil water retention curves, were obtained by two approaches, namely by the Representative Elementary Volume approach (REVa) and by the inverse modelling with Hydrus-1D model (IMa). The soil water outflow hydrographs simulated by Hydrus-2D were compared to catchment runoff hydrographs by analysing their skewness and peak times. Measured catchment runoff hydrographs were similar to simulated soil water outflow hydrographs for about a half of rainfall events. Interestingly, most of them were caused by rainfalls with small intensity (below 2.5 mm/10 min). The REV approach to derive soil hydraulic parameters for soil water outflow modelling provided more realistic shapes of soil water outflow hydrographs and peak times than the IMa approach.