IMPACT OF SPRUCE FOREST ON RAINFALL INTERCEPTION AND SEASONAL SNOW COVER
EVOLUTION IN THE WESTERN TATRA MOUNTAINS, SLOVAKIA
Ladislav Holko1, Jaroslav Skvarenina2, Zdenek Kostka1 Michal Fric2, Juraj Staron2
1Institute of Hydrology SAS, Ondrasovska 16, 031 05 Liptovsky Mikulas, Slovakia; tel./fax.: (+42144)
5522522, E-mail: holko@uh.savba.sk
2Technical University Zvolen, 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
(Fig. 1). Both processes were monitored at the elevation of 1420 m a.s.l.. The interception was
measured from the end of August 2006 until November 2008 by a network of 13 raingauges. The
papers describes interception variability at characteristic position in the forest, i.e. in forest window, in
the dripping zone (under the braches of the trees), near the stems of the trees and under the young
spruce trees (understorey). Measurements at each characteristic position were tripled.
A
B
Fig. 1. A- research plot used to measure forest interception and snow characteristics in the forest; Bthe open area where the snow characteristics were measured; meteorological station at this site
provided also the data on numbers of rainy days and data for snow modelling.
Mean interception over the studied period in forest window was 23%. Mean values for the dripping
zone, the near stem zone and the young trees were 28%, 65% and 44%, respectively. With exception
of forest window, the interception at the same characteristic positions was highly variable (Table 1,
Fig. 2).
Table 1. Statistics of interception measurements shown in Fig. 2; period 21 August 2006-9 November
2008; negative values mean higher precipitation than in the open area.
Interception[%]
Mean
Minimum
Maximum
Standard deviation
n
Forest window
23
0
81
15
87
Dripping zone
28
-65
88
34
87
Near stem
65
-20
100
27
88
Young trees
44
-37
100
28
75
Equation developed by de Groen & Savenije (2006) was used to calculate daily precipitation
thresholds needed to fulfill the storage capacity of the canopy:

 Dn
I m  Pm 1  exp  r
 Pm


 


where Im is monthly interception, Pm is monthly precipitation (at the open area), D is the daily
threshold, nr is number of rainy days in a month. Calculated daily precipitation thresholds 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
(Fig. 3) 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.
Window
IC [%]
80
40
0
-40
Dripping zone
IC [%]
80
40
0
-40
IC [%]
80
40
0
Near stem
-40
IC [%]
80
40
0
Young trees
21-Oct-08
20-Sep-08
20-Aug-08
20-Jul-08
19-Jun-08
19-May-08
18-Apr-08
18-Mar-08
16-Feb-08
16-Jan-08
16-Dec-07
15-Nov-07
15-Oct-07
14-Sep-07
14-Aug-07
14-Jul-07
13-Jun-07
12-Apr-07
13-May-07
12-Mar-07
9-Jan-07
9-Feb-07
9-Dec-06
8-Oct-06
8-Nov-06
7-Sep-06
-40
Fig. 2. Interception at characteristic positions from September 2006 to November 2008; the symbol
are used just to identify each of the 3 raingauges without any further importance (therefore the legend
is not given); negative values mean that precipitation was higher than at open area.
160
600
SWEF=0.716*SWEO-4.82
n=81, R2=0.876
120
SWE forest [mm]
SD forest [cm]
SDF=0.85*SDO-3.88
n=82, R2=0.915
80
40
0
400
200
0
0
40
80
120
SD open area [cm]
160
0
200
400
SWE open area [mm]
600
Fig. 3. Relationships between snow characteristics (SD and SWE) measured in the open area and in
the forest, the regression lines (grey) and the 1:1 lines (black).
Key words: spruce forest, mountains, interception, snow cover, energy based snow model.
References
De Groen M.M., & Savenije H.H.G. 2006. A monthly interception equation based on the statistical
characteristics of daily rainfall. Water Resour. Res. 42: W12417, doi:10.1029/2006WR005013.