Drought is a natural phenomenon that, in recent years, happens more and more frequently due to climate change and affects various regions almost all over the world. The lack of precipitation and its uneven distribution causes problems also in Slovenia. In the past, there has been no extensive analysis of hydrological drought in Slovenia even though it causes damage in energetics, water distribution, industry and tourism. The main objective of the master's thesis is therefore to provide a more extensive temporal and spatial analysis of hydrological droughts in Slovenia.
In temporal and spatial analysis of the largest hydrological droughts in Slovenia, 44 gauging stations were included, to ensure good geographical coverage of the Slovenian territory. Included gauging stations have accessible hydrological data sets without longer gaps of missing data. First, low-flow indices were calculated for the entire data set for each gauging station and then, on the basis of those results, the years with the most severe hydrological droughts were identified. Since the majority of selected gauging stations have overlapping river flow recordings for the 1960–2016 period, analysis was carried out for this interval for drought events in identified years 1993, 2003, 2011 and 2012. The years 1971 and 1989 were added to the first part of the analyses. This first part deals with the comparison of volumes and durations of drought deficits calculated using the threshold method for different selected thresholds for three gauging stations. The second part of the analysis describes the method of identifying the most severe drought stricken years on the diagram of mean annual minima MAM(n) for different durations. Furthermore the specific mean annual minima MAM(180) for moving average of 180 days and specific mean annual minima for the 180-day duration for August MAM(180)avg were shown. In addition MAM(n)avg of 7-, 30-, 180- and 360-day durations for the year 1993 were presented. Lastly, calculations of standardized volumes and durations of drought deficits were executed and graphically presented.
On the basis of executed analysis and previous findings of other authors we concluded that the year with the most severe drought after the 1960 was the year of 2003 when drought affected mainly north-eastern part of Slovenia. The same area was affected by a milder drought in 2012. In the year 1993, drought events were most severe in the northern, eastern and north-eastern part of the country. The least severe droughts were present in 2011 when drought events happened in the southern part of Slovenia.