| Summary: | Water retention and runoff formation have been studied in two basins located in the Giant Mts (Krkonoše in Czech, Karkonosze in Polish). The Labe basin (LB: area 53.06 km2, altitude 692 to 1,503 m a.s.l.), and the Modrý Potok basin (MP: area 2.62 km2, altitude 1,010 to 1,554 m a.s.l.) are located in the same natural conditions. The bedrock is formed by rocks of the crystalline complex. The prevailing soil types are Humic Podzols, Lithic Leptosols, and Dystric Histosol. The vegetative cover is formed by grass and spruce forest in the lower part, and artic-alpine tundra with dwarf pine in the upper part above the timberline. In September 2001, unusual rainfall of 348 mm/mo (LB) and 364 mm (MP) fell. Consequently, a runoff of 281 mm/mo (LB) and 262 mm/mo (MP) was generated. The maximum retention of water in the basin was 80 mm (LB) and 140 mm (MP). At the moment of peak runoff, water retention in the basins captured 40 % (LB) and 65 % (MP) of previous cumulative rain. In the Labe basin, anomalous fi ll-spill effect was observed: water supplied by rain caused a decrease of 40 mm in the soil water content. This resulted in a reduction of the water retention by 5 mm in the Labe basin. The conclusion, gained in both basins, is that the retention of water in the basin and particularly in the soil profi le signifi cantly reduced the peak runoff from the watershed.
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