Snow accumulation and melt are highly variable. Therefore, correct modeling of spatial variability of the snowmelt, timing and magnitude of catchment runoff still represents a challenge in mountain catchments for flood forecasting. The article presents the setup and results of detailed field measurements of snow related characteristics in a mountain microcatchment (area 59 000 m2 , mean altitude 1509 m a. s. l.) in the Western Tatra Mountains, Slovakia obtained in winter 2015. Snow water equivalent (SWE) measurements at 27 points documented a very large spatial variability through the entire winter. For instance, range of the SWE values exceeded 500 mm at the end of the accumulation period (March 2015). Simple snow lysimeters indicated that variability of snowmelt and discharge measured at the catchment outlet corresponded well with the rise of air temperature above 0°C. Temperature measurements at soil surface were used to identify the snow cover duration at particular points. Snow melt duration was related to spatial distribution of snow cover and spatial patterns of snow radiation. Obtained data together with standard climatic data (precipitation and air temperature) were used to calibrate and validate the spatially distributed hydrological model MIKE-SHE. The spatial redistribution of input precipitation seems to be important for modeling even on such a small scale. Acceptable simulation of snow water equivalents and snow duration does not guarantee correct simulation of peakflow at shorttime (hourly) scale required for example in flood forecasting. Temporal variability of the stream discharge during the snowmelt period was simulated correctly, but the simulated discharge was overestimated.
The paper provides basic information on hydrological research performed in the mountain catchment of the Jalovecký creek, the Western Tatra Mountains by the Institute of Hydrology of the Slovak Academy of Sciences since the mid-1980-ties. The research was devoted to better understanding of spatial distribution of precipitation, soil moisture, snow cover, evapotranspiration and runoff generation. First part of the paper brings an overview of the results. Second part of the paper is devoted to the water balance of the catchment in hydrological years 1989-2005 and estimation of mean transit time of water in the catchment as given by the tracer method using the stable environmental isotope of 18O. Catchment mean annual precipitation in the studied period was 1562 mm. It varied from 1116 mm in the year of 2003 to 1854 mm in 2001. Mean annual runoff was 1015 mm and it varied between 703 mm in 2003 and 1284 mm in 1998. Mean annual air temperature at catchment mean elevation (1500 m a.s.l.) was 3.5 °C. Interpertation of δ18O in precipitation and runoff from the period 1991-2002 gave the mean transit time of 13 months. Direct application of measured values in precipitation provided more realistic results than the input data series prepared according to recommendations found in the literature. and Príspevok poskytuje základné informácie o hydrologickom výskume, ktorý vykonáva od druhej polovice 80. rokov 20. storočia Ústav hydrológie SAV v horskom povodí Jaloveckého potoka v Západných Tatrách. Výskum poskytol poznatky o priestorovom rozdelení atmosférických zrážok, vlhkosti pôdy, snehovej pokrývke, evapotranspirácii a tvorbe odtoku vo vysokohorskom prostredí. Stručný prehľad niektorých z nich uvádzame v prvej časti príspevku. Druhá časť príspevku za zaoberá hydrologickou bilanciou povodia za obdobie 1989-2005 a určením priemernej doby prechodu vody povodím pomocou metódy stopovačov, pričom bol použitý stabilný prírodný izotop kyslíka 18O. Priemerný ročný úhrn zrážok v povodí v období 1989-2005 bol 1562 mm (od 1116 mm roku 2003 do 1854 mm v roku 2001). Priemerný ročný odtok z povodia bol 1015 mm (od 703 mm v roku 2003 do 1284 mm v roku 1998). Priemerná ročná teplota vzduchu v priemernej nadmorskej výške povodia 1500 m n.m. bola 3,5 °C. Interpretáciou hodnôt δ18O v zrážkach a v odtoku za obdobie 1991-2002 bola určená priemerná doba prechodu 13 mesiacov, čo je časový úsek porovnateľný s tradičným hydrologickým rokom. Použili sme pritom dve varianty prípravy hodnôt δ18O v zrážkach (vstup do hydrologického cyklu povodia). Priame použitie meraných hodnôt dalo realistickejší výsledok, ako rad vstupných hodnôt upravený podľa odporúčaní z literatúry.
Large-scale forest dieback was reported in recent decades in many parts of the world. In Slovakia, the most endangered species is Norway spruce (Picea Abies). Spruce dieback affects also indigenous mountain forests. We analysed changes in snow cover characteristics in the disturbed spruce forest representing the tree line zone (1420 m a.s.l.) in the Western Tatra Mountains, Slovakia, in five winter seasons 2013–2017. Snow depth, density and water equivalent (SWE) were measured biweekly (10–12 times per winter) at four sites representing the living forest (Living), disturbed forest with dead trees (Dead), forest opening (Open) and large open area outside the forest (Meadow). The data confirmed statistically significant differences in snow depth between the living and disturbed forest. These differences increased since the third winter after forest dieback. The differences in snow density between the disturbed and living forest were in most cases not significant. Variability of snow density expressed by coefficient of variation was approximately half that of the snow depth. Forest dieback resulted in a significant increase (about 25%) of the water amount stored in the snow while the snowmelt characteristics (snowmelt beginning and time of snow disappearance) did not change much. Average SWE calculated for all measurements conducted during five winters increased in the sequence Living < Dead < Meadow < Open. SWE variability expressed by the coefficient of variation increased in the opposite order.