LONG-TERM VARIABILITY OF WATER RESOURCES IN MOUNTAINOUS AREAS: CASE STUDY - KLODZKO REGION (SW POLAND)

The variability of water resources in the Klodzko region located in SW Poland is presented through the characteristics of total and groundwater runoff. On the basis of daily river flow were determined the average monthly flow (SQ) values were used to determine total runoff and the average low river flows (NQ) were in turn used to determine groundwater runoff. Based on the obtained results, the Nysa Klodzka river basin should be classified as an area characterized by high hydrological activity. The average water resources for the period 1967-2016 were 13.01 m(3)/s and they accounted for 50 % of the precipitation (751 mm). The average values of dynamic groundwater resources were calculated at 4.75 m(3)/s, which accounted for 36 % of the total water resources and 19 % of the precipitation. The total runoff variability is relatively high, as evidenced by the ratio of the maximum and minimum long-term annual runoff, which was 2.83. A higher value was found in the case of groundwater runoff (4.4). Based on the analysis of the volume of water resources, in particular during the last decade (2007-2016), we can see the decreasing percentage of groundwater resources in the total water balance of the study area (16 %), while in the hydrological year 2016 the percentage contribution of the groundwater runoff was only 8 percent. In analyzing the variability of total and groundwater runoff, decreasing long-term trends in total and groundwater runoff can be observed. It is primarily affected by very noticeable declining trends during the summer period, which relates to both total and groundwater runoff. During the winter period, a slight decreasing trend in groundwater runoff can only be seen, with simultaneous stabilization of the total runoff. The knowledge of the temporal variability of the river basin runoff can form the basis for further research on the water cycle within the Klodzko region area.