Zdeněk Kostka

Impact of spruce forest on rainfall interception and seasonal snow cover evolution in the Western Tatra Mountains, Slovakia

The paper analyzes the impacts of the spruce forest on precipitation interception and evolution of snow cover in the mountain catchment of the Jalovecký creek, the Western Tatra Mountains, Slovakia. Both processes were monitored at the elevation of 1420 m a.s.l.. Interception was measured from the end of August 2006 until November 2008 by a network of 13 raingauges. Mean interception over the studied period in forest window was 23%. Mean values for the dripping zone under tree branches, near stems of the trees and under the young trees were 28%, 65% and 44%, respectively. With exception of forest window, the interception at the same characteristic positions was highly variable. Calculated daily precipitation thresholds needed to fulfill the storage capacity of the canopy were about 0.8–0.9 mm.Differences in snow accumulation and melt in the open area (elevation 1500 m a.s.l.) and in the forest were measured in winters 2003–2008. Snow depths (SD) and water equivalents (SWE) were typically smaller in the forest, although the differences were getting smaller towards the end of snow season. SD and SWE in the forest were higher than in the open area for a short time before the end of season in winters 2003 and 2005. The correlations between SD and SWE in the open area and in the forest explained about 90% of variability. The energy balance snow model UEB satisfactorily simulated the evolution of snow cover in the forest and in the open area.

Variation of nitrates in runoff from mountain and rural areas

The paper presents results of temporal and spatial variation of nitrates in streamwater in the small mountain catchment of the Jalovecký creek, the Western Tatra Mountains, Slovakia. Water samples were collected between October 2003 and April 2005 in areas with contrasting catchments. Water samples collected at the outlet of the mountain part (almost no human activities) had lower concentrations of nitrates than the samples collected donwstream in the rural area. The differences were smaller during the warm period of the year. The highest concentrations of nitrates and the highest differences among the uninhabited and inhabited areas were observed at the time of snowmelt. Samples collected along the creek in March and April 2005 showed increasing concentrations with increasing urbanization. Concentrations of nitrates measured during springs 1992, 2004 and 2005 were in similar range. Higher frequency sampling during the summer rainfall-runoff event indicated that concentrations of nitrates in the creek varied during the event. Water samples from snow had low concentrations of nitrates.

Basin-Wide Water Balance in the Danube River Basin

This paper briefly describes the result of mutual work of the IHP UNESCO National Committees of the Danube countries and experts and scientists nominated by their countries. It represents part of the second phase of the co-operation of Danube countries within the frame of the IHP UNESCO in the field of hydrology. This project in fact represents a continuation, improvement and enlargement of the first Danube Monograph (Stancik et al. 1988, Hydrology of the River Danube, Publishing House Priroda, Bratislava). The main objectives of the work were estimation of water balance components on the basis of mathematical modelling and preparation of maps of water balance components for the Danube Basin. Maps of the mean annual precipitation, actual evapotranspiration and runoff were prepared. Difficulties in data collection in individual countries resulted in the obligatory period for data analysis of 1961–1990.

The influence of stony soil properties on water dynamics modeled by the HYDRUS model

Abstract Stony soils are composed of two fractions (rock fragments and fine soil) with different hydrophysical characteristics. Although stony soils are abundant in many catchments, their properties are still not well understood. This manuscript presents an application of the simple methodology for deriving water retention properties of stony soils, taking into account a correction for the soil stoniness. Variations in the water retention of the fine soil fraction and its impact on both the soil water storage and the bottom boundary fluxes are studied as well. The deterministic water flow model HYDRUS-1D is used in the study. The results indicate that the presence of rock fragments in a moderate-to-high stony soil can decrease the soil water storage by 23% or more and affect the soil water dynamics. Simulated bottom fluxes increased or decreased faster, and their maxima during the wet period were larger in the stony soil compared to the non-stony one.

Experimental measurements for improved understanding and simulation of snowmelt events in the Western Tatra Mountains

Abstract 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 short-time (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.

Hydrological Effects of a Large Scale Windfall Degradation in the High Tatra Mountains, Slovakia

Influence of deforestation on hydrological cycle has been a subject of numerous studies since the beginning of the 20th century. A temporary increase of discharges after deforestation was typically reported (e.g. Bosch and Hewlett, 1982), but the measured data often show that“.. flood and erosion control functions of the forests become to be evident but only in a limited way...” (Biba et al., 2006). A recent review of the articles dealing with the influence of forests on runoff can be found e.g. in Kostka and Holko (2006). Extraordinary wind induced deforestation which took place on 19 November 2004 in the High Tatra Mountains initiated a multidisciplinary international research.