Izbira sušnega indeksa za razglasitev hidrološke suše površinskih voda v Sloveniji : magistrsko delo

Zalokar, Lenka (author), Šraj, Mojca (mentor), Kobold, Mira (co-mentor)

Suša predstavlja kompleksen naravni pojav, ki je povezan z razpoložljivostjo vodnih zalog in vpliva na različne ekosisteme. Zaradi njene kompleksnosti jo je težko definirati, kvantificirati ter spremljati. Posebno pozornost smo v magistrski nalogi posvetili hidrološki suši, ki je v primerjavi z meteorološko sušo precej manj raziskana. Tako smo v prvem delu naloge pripravili pregled različnih vrst kazalnikov (indeksov), s pomočjo katerih lahko definiramo hidrološko sušo. Za študijo hidrološke suše površinskih voda v Sloveniji smo uporabili standardizirani indeks pretoka (SSI) in sušni indeks pretoka (SDI). Oba indeksa smo računali na različnih časovnih skalah, s čimer tudi lažje definiramo začetek, trajanje in intenziteto hidrološke suše. Edini vhodni podatek za izračun omenjenih indeksov predstavljajo podatki o pretokih. Ker je osnovna metoda izračuna obeh indeksov analogna metodologiji izračuna standardiziranega padavinskega indeksa (SPI), smo indekse pretoka za izbrane hidrološke postaje izračunali s pomočjo programskih orodij SPI in DrinC, ki sta sicer namenjena izračunu padavinskega indeksa. V zadnjem delu naloge smo analizirali rezultate izračunanih indeksov in naredili primerjavo SDI indeksa izračunanega z dvema različnima porazdelitvama, in sicer z gama in logaritemsko normalno porazdelitveno funkcijo. Pri primerjavi indeksov SSI in SDI smo ugotovili, da podajata enake rezultate, zato smo v nadaljevanju analizirali le SSI. Ugotovili smo, da je variabilnost indeksa večja na krajših časovnih skalah kot pa na daljših. Na izbranih hidroloških postajah v Sloveniji, smo prikazali prostorsko porazdelitev vrednosti indeksov za tipično mokro (1965) in suho leto (2003). Rezultate indeksa za suho leto 2003 smo v nadaljevanju z uporabo programskega orodja Orange analizirali tudi s pomočjo t.i. kart jakosti. Za izbrane hidrološke postaje smo dodatno določili število hudih in ekstremnih suš ter postaje razvrstili v skupine glede na podobnost pojavljanja suš s pomočjo metode hierarhičnega razvrščanja. Ugotovili smo, da suša ne zajame vseh območij Slovenije enakomerno, temveč gre za regionalen pojav.

• Language: Slovenian
• Keywords: Suša, hidrološki sušni indeksi, standardizirani padavinski indeks, standardizirani indeks pretoka, sušni indeks pretoka.
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Publisher: [L. Zalokar]
• Year: 2018
• PID: 20.500.12556/RUL-101125
• UDC: 551.577.38(497.4)(043.3)
• COBISS.SI-ID: 8418145
• Publication date in RUL: 27.04.2018

Secondary language

• Language: English
• Title: Choice of a drought index for the announcement of hydrological drought of surface waters in Slovenia : master thesis

Abstract

Drought is a complex natural hazard, connected with water availability, that affects different ecosystems. Because of its complexity it is hard to define, qualify and monitor. In this master thesis, special attention was given to the hydrological drought, which is less investigated compared to the meteorological drought. In the first part of the master thesis, we did the overview of different indicators (indices) with which we can define hydrological drought. For study of hydrological drought on surface waters in Slovenia, we used standardized streamflow index (SSI) and streamflow drought index (SDI). We calculated both drought indices on different time scales so it is easier to define the beginning, duration and intensity of hydrological drought. The only input data for the calculation of both indices are time series data of discharges. Because the basic method of calculation of both indices is analogic to the method of calculation of standardized precipitation index (SPI), we used SPI and DrinC software to calculate indices for chosen hydrological stations. In the final part of the thesis, we analysed results of calculated indices and made comparison of SDI index calculated with two different distributions, namely gama and log normal distribution. Comparison of SSI and SDI indices showed that both methods gave equal results, so further analyses, were made only for SSI index. We discovered that the variability of SSI is higher on longer time scales than on shorter ones. We presented spatial distribution of indices for a typically wet (1965) and a dry year (2003) for chosen hydrological stations in Slovenia. Furthermore, we analysed index results for a dry year of 2003 with Orange software, using heatmaps. For chosen hydrological stations, we defined the number of severe and extreme droughts. We sorted the hydrological stations into groups by similarity of drought events using hierarchical clustering method. We discovered that drought doesn’t affect all regions in Slovenia evenly, but is rather a regional phenomen.

• Keywords: Drought, hydrological drought indices, standardized precipitation index, standardized streamflow index, streamflow drought index.