The climatic variability and climate changes in the geological history of Earth are correlated with the environmental development. A special attention is paid to the impact of changing climate on the water resources and hydrological cycle. Possible impact of man's activities on the climatic variability is also discussed. Can the regulation of such activities slow down or bring to a stop the forthcoming climate change? A comparison of data from the Holocene period and from modern history indicates that the climatic variability and climate change have been always produced by external periodic phenomena and occasional cataclysmic events. In other words, the climate has never been stable and administrative measures limiting man's influence on the climate can bring only partial results. Considering that the climatic change is an unavoidable process, following measures should be taken: First, alternative scenarios of possible climatic development, would it be cooling or warming, should be set up. Second, preventive and protective methodologies need to be prepared for each scenario well in advance. Third, technologies facilitating man's survival and everyday life under changed climatic situation should be developed. and Klimatická variabilita a změny klimatu jsou sledovány v geologické historii Země a korelovány s historií životního prostředí. Zvláštní pozornost se věnuje vlivu měnícího se klimatu na vodní zdroje a hydrologický cyklus. Také je diskutován vliv činnosti člověka ve vztahu ke klimatu. Je možné redukcí takových aktivit zpomalit nebo zcela zastavit klimatické změny? Porovnání dat z holocénu a moderní historie ukazuje, že klimatická variabilita a změny byly vždycky vyvolávány mimozemskými periodickými vlivy, případně občasnými katastrofickými jevy. Jinými slovy, klima nikdy nebylo stabilní. Proto také administrativní opatření, omezující vliv člověka na klima, mohou být úspěšná pouze do jisté míry. Uvážíme-li, že klimatická variabilita i její hydrologické následky jsou nevyhnutelné, je třeba připravit příslušné scénáře možných klimatických změn, ať už souvisí s ochlazováním nebo oteplováním. Pro každý ze scénářů je třeba navrhnout metody preventivních a ochranných opatření s dostatečným předstihem. Konečně bude třeba vypracovat nové technologie usnadňující život člověka ve změněných klimatických podmínkách.
Povodně a sucho se v posledních letech skloňují ve všech pádech. Často se v tomto kontextu zmiňuje potřeba budování přehrad a dalších nákladných děl, která však řeší jen důsledek mnohdy špatné péče o krajinu. Ne každý si totiž uvědomuje, jak důležitou roli hraje v koloběhu vody půda a stav krajiny. Kvalitní a nedegradovaná půda dokáže poutat značné množství vody, čímž reguluje dopady obou klimatických extrémů. Pestrá krajina s přirozenými mokřady a dalšími krajinnými prvky s vodou hospodaří lépe než krajina plná velkých půdních bloků s monokulturami zemědělských plodin a regulovanými vodními toky. and Jiří Hladík, Jan Vopravil, Marek Batysta.
Hydrologic cycle in the Liz catchment is described with an anomaly in the vegetation seasons 1992-1996. Experimental catchment Liz is located in the Šumava Mts. in the Czech Republic. The fully forested watershed is covered by mature spruce forest, and its basic characteristics are as follows: drainage area 0.99 km2, mean discharge 0.01m3 s-1, runoff coefficient 0.38, mean annual air temperature 6.30 oC, average slope 17 %, basin length 1.45 km, water course length 1.43 km, elevation 828-1074 m a.s.l., precipitation sum 851 mm year-1, and runoff depth 324 mm year-1. Air temperature, precipitation, global radiation, and discharge in the closing profile are measured in the catchment. It is characteristic for hydrologic cycle in the catchment that the share of seasonal sums of both the global radiation and temperature was nearly constant in 1983-2000. However, the seasonal sums of both the global radiation and temperature were changed considerably in 1983-2000. Similarly, the share of seasonal sums of both the rainfall and runoff was nearly constant in 1983-1991 and 1997-1999. An anomalous course of climate was registered in 1992-1996, manifested by a deviation on the double mass curve of the seasonal sums of rainfall and runoff. Stabilised elsewhere, the ratio of rainfall and runoff is changed during the vegetation seasons 1992-1996. Starting from the 1997 season, this ratio has obtained the value held before 1992. The reason of the 1992-1996 anomaly of hydrologic cycle in the experimental catchment had to be significant external phenomenon, most likely explosion of the Mount Pinatubo volcano in Philippines on June 15, 1991. and Hydrologic cycle in the Liz catchment is described with an anomaly in the vegetation seasons 1992- 1996. Experimental catchment Liz is located in the Šumava Mts. in the Czech Republic. The fully forested watershed is covered by mature spruce forest, and its basic characteristics are as follows: drainage area 0.99 km2 , mean discharge 0.01m3 s -1, runoff coefficient 0.38, mean annual air temperature 6.30 ºC, average slope 17 %, basin length 1.45 km, water course length 1.43 km, elevation 828-1074 m a.s.l., precipitation sum 851 mm year-1, and runoff depth 324 mm year-1. Air temperature, precipitation, global radiation, and discharge in the closing profile are measured in the catchment. It is characteristic for hydrologic cycle in the catchment that the share of seasonal sums of both the global radiation and temperature was nearly constant in 1983-2000. However, the seasonal sums of both the global radiation and temperature were changed considerably in 1983-2000. Similarly, the share of seasonal sums of both the rainfall and runoff was nearly constant in 1983-991 and 1997-1999. An anomalous course of climate was registered in 1992-1996, manifested by a deviation on the double mass curve of the seasonal sums of rainfall and runoff. Stabilised elsewhere, the ratio of rainfall and runoff is changed during the vegetation seasons 1992-1996. Starting from the 1997 season, this ratio has obtained the value held before 1992. The reason of the 1992-1996 anomaly of hydrologic cycle in the experimental catchment had to be significant external phenomenon, most likely explosion of the Mount Pinatubo volcano in Philippines on June 15, 1991.