Changes in Cerknica Lake water level during 1958–2019

Podnebje se v zadnjih desetletjih naglo spreminja, kar se odraža tudi na pretočnem režimu vodotokov in vodostaju jezer. V magistrskem delu smo poskušali oceniti vpliv podnebnih sprememb na spreminjanje vodostaja presihajočega Cerkniškega jezera. Za obdobje med letoma 1958 in 2019 so bile na letni in sezonski ravni izdelane analize trendov višine padavin in snežne odeje, temperature zraka ter najnižjega, srednjega in najvišjega vodostaja jezera. Ugotovili smo, da je trend temperature zraka tako kot drugje po Sloveniji naraščajoč in statistično značilen. Trend višine padavin je padajoč, statistično je značilen le poleti. Trendi najnižjega, srednjega in najvišjega vodostaja Cerkniškega jezera so negativnistatistično značilna sta trenda srednjega in najvišjega vodostaja. Višina srednjega vodostaja se je v proučevanem obdobju glede na enačbo linearnega trenda znižala za 42 cm, višina najnižjega vodostaja za 20 cm, višina najvišjega vodostaja pa za 144 cm. Spomladi in poleti so trendi najnižjega, srednjega in najvišjega vodostaja negativni. Z izjemo poletnega najnižjega in srednjega vodostaja so vsi statistično značilni. V jesenskem času pri srednjem vodostaju trend ni bil zaznan, trend najnižjega vodostaja je pozitiven, trend najvišjega vodostaja pa negativen in prav tako statistično neznačilen. Pozimi so trendi vodostajev Cerkniškega jezera sicer negativni, a statistično neznačilni. Zaradi vključitve zgolj treh meteoroloških spremenljivk je ocena vpliva podnebnih sprememb na spreminjanje vodostaja Cerkniškega jezera zgolj okvirna. A glede na povezave med analiziranimi meteorološkimi in hidrološkimi spremenljivkami vseeno ocenjujemo, da je spreminjanje vodostaja Cerkniškega jezera v proučevanem obdobju v veliki meri posledica podnebnih sprememb. Pomemben vpliv na spreminjanje vodostaja pa ima zagotovo tudi človek z različnimi posegi, ki jih na Cerkniškem jezeru v preteklosti ni bilo malo. Ob nadaljevanju obstoječih trendov bo spreminjanje vodostaja lahko vplivalo predvsem na drsanje pozimi, dolgotrajna sušna obdobja pa bodo onemogočala čolnarjenje ter hkrati omogočala košnjo, ki je izrednega pomena pri ohranjanju primernega okolja za živalske in rastlinske vrste.In recent decades, the rapidly changing climate has affected the flow regime of watercourses and water levels of lakes. In this master\u27s thesis, we tried to assess the impact of climate change on the changing water level at the intermittent lake in Cerknica. Between 1958 and 2019, annual and seasonal trend analyses of precipitation levels, snow cover, air temperatures, and the lowest, mean as well as the highest water levels of the lake were made. We found that the air temperature in Cerknica, as well as elsewhere in Slovenia, is increasing and is statistically significant. The precipitation trend is declining and is only statistically significant in summer. Trends of the lowest, mean, and the highest water levels at Lake Cerknica are negative, whereby trends of the mean and the highest water levels are statistically significant. According to the linear trend equation, the height of the mean water level decreased by 42 cm, the height of the lowest water level by 20 cm, and the height of the highest water level by 144 cm during our study period. In spring and summer, trends of the lowest, the mean, and the highest water levels are negative. Except for the lowest and the mean water levels in the summer, they are all statistically significant. In autumn, there is no sign of a mean water level trend. The trend of the lowest water level is positive. The highest water level trend is negative and also statistically insignificant. In winter, the water level trends at Lake Cerknica are negative, but statistically insignificant. Since we only analyzed three meteorological variables, the assessment of climate change impact on water level changes at Lake Cerknica is only indicative. However, the analyzed meteorological and hydrological variables are connected. Therefore, we still estimate that climate change significantly impacts water level changes at Lake Cerknica. Humans significantly impact the changing water level of the lake with their encroachment on nature, which was certainly not uncommon around Lake Cerknica in the past. Should existing trends continue, changes in water levels will affect ice skating in winter. Long periods of drought will prevent boating but at the same time allow mowing, which is extremely important in maintaining a suitable environment for animal and plant species