We analyzed the runoff and its temporal distribution during the catastrophic flood events on river Gidra (32.9 km2 ) and Parná (37.86 km2 ) of the 7th June 2011. The catchments are located in the Small Carpathian Mountains, western Slovakia. Direct measurements and evaluation of the peak discharge values after such extreme events are emphasized in the paper including exceedance probabilities of peak flows and of their causal flash rainfall events. In the second part of the paper, plausible modeling mode is presented, using the NLC (Non Linear Cascade) rainfall-runoff model. Several hypothetical extreme flood events were simulated by the NLC model for both rivers. Also the flood runoff volumes are evaluated as basic information on the natural or artificial catchment storage. and Predložený príspevok analyzuje tvorbu a priebeh odtoku počas katastrofickej povodňovej situácie na Gidre (32,9 km2 ) a na Parnej (37,86 km2 ) dňa 7. 6. 2011. Povodia týchto tokov sa nachádzajú v Malých Karpatoch na západnom Slovensku. V príspevku sa kladie dôraz na priame zameranie a vyhodnotenie kulminačných prietokov po výskyte takýchto povodní. Diskutujú sa problémy vyjadrenia pravdepodobnosti prekročenia kulminačných prietokov a dažďov, ktoré ich spôsobili. V druhej časti príspevku je prezentovaný možný spôsob modelovania povodne jednoduchým zrážkovo-odtokovým modelom NLC. Daným modelom NLC sú následne simulované prietoky Gidry v stanici Píla a Parná v stanici Horné Orešany za extrémnej hypotetickej zrážkovej udalosti. Hodnotené sú objemy odtoku počas povodní, ako základný údaj pre reálny odhad ich prirodzeného alebo umelého zadržania.
Changes in runoff parameters are very important for Slovakia, where stream-flow discharges, being supplied by precipitation and groundwater runoff, are preferentially influenced by climatic conditions. Therefore, teleconnections between runoff parameters, climate parameters and global atmospheric drivers such as North Atlantic Oscillation, Southern Pacific Oscillation, Quasi-biennial oscillation and solar activity were studied in the Nitra River Basin, Slovakia. Research was mostly based on records of 80 years (1931-2010) for discharges and baseflow, and 34 years for groundwater heads. Methods of autocorrelation, spectral analysis, cross-correlation and coherence function were used. Results of auto-correllograms for discharges, groundwater heads and base flow values showed a very distinct 11-year and 21-year periodicity. Spectrogram analysis documented the 11-year, 7.8-year, 3.6-year and 2.4-year periods in the discharge, precipitation and air temperature time series. The same cycles except of 11-years were also identified in the long-term series of the North Atlantic Oscillation and Southern Pacific Oscillation indices. The cycle from approximately 2.3 to 2.4-years is most likely connected with Quasi-biennial oscillation. The close negative correlation between the North Atlantic Oscillation winter index and the hydrological surface and groundwater parameters can be used for their prediction within the same year and also for one year in advance.
In this paper we focused on the history of floods and extreme flood frequency analysis of the upper Danube River at Bratislava. Firstly, we briefly describe the flood marks found on the Danube River in the region of Bratislava, Slovakia, and provide an account of the floods’ consequences. Secondly, we analyzed the annual maximum discharge series for the period 1876–2012, including the most recent flood of June 2013. Thirdly, we compare the values of T-year design discharge computed with and without incorporating the historic floods (floods of the years 1501, 1682, and 1787 into the 138-year series of annual discharge peaks). There are unfortunately only a few historic flood marks preserved in Bratislava, but there are very important and old marks in neighbouring Hainburg and other Austrian cities upstream to Passau. The calculated T-year maximum discharge of the Danube at Bratislava for the period 1876-2010 without and with historic flood values have been compared. Our analysis showed that without incorporating the historic floods from the years 1501, 1682, and 1787 the 1000-year discharge calculated only with data from the instrumented period 1876- 2013 is 14,188 m3 s -1 , and it is lower compared to the 1000-year discharge of 14,803 m3 s -1 when the three historic floods are included. In general, the T-year discharge is higher throughout the whole spectrum of T-year discharges (10, 20, 50, 100, 200, 500-year discharge) when the three historic floods are included. Incorporating historic floods into a time series of maximum annual discharge seems to exert a significant effect on the estimates of low probability floods. This has important implications for flood managements and estimation of flood design discharge.
The problem of understand natural processes as factors that restrict, limit or even jeopardize the interests of human society is currently of great concern. The natural transformation of flood waves is increasingly affected and disturbed by artificial interventions in river basins. The Danube River basin is an area of high economic and water management importance. Channel training can result in changes in the transformation of flood waves and different hydrographic shapes of flood waves compared with the past. The estimation and evolution of the transformation of historical flood waves under recent river conditions is only possible by model simulations. For this purpose a nonlinear reservoir cascade model was constructed. The NLN-Danube nonlinear reservoir river model was used to simulate the transformation of flood waves in four sections of the Danube River from Kienstock (Austria) to Štúrovo (Slovakia) under relatively recent river reach conditions. The model was individually calibrated for two extreme events in August 2002 and June 2013. Some floods that occurred on the Danube during the period of 1991-2002 were used for the validation of the model. The model was used to identify changes in the transformational properties of the Danube channel in the selected river reach for some historical summer floods (1899, 1954 1965 and 1975). Finally, a simulation of flood wave propagation of the most destructive Danube flood of the last millennium (August 1501) is discussed.
The procedure for identification of the long-term trends in the individual water quality determinands in surface water is described in the study. The methodology is based on requirements of the Directive 2000/60/EC and the existing water quality data in the database of the Slovak Hydrometeorological Institute. The methodology gives guidance for estimation of following issues: - influence of the length of the series on trends of development; - methods for calculation of the statistical characteristics; - methods for identification of the increasing and decreasing trends, as well as of the trend reversal point; - selection of the decision criteria for assessment of the trend significance. The methodology was applied for the trend analysis of the selected pollutants in the middle part of Hron River at Salkova near Banska Bystrica city. The results show that the rapid increase of pollution in 1970`s is followed by gradual improvement of the surface water quality in next period. and V predloženej štúdii je opísaný postup pri identifikácii dlhodobých trendov jednotlivých ukazovateľov kvality vody v povrchových tokoch. Pri vypracovaní metodiky sa vychádzalo z požiadaviek smernice 2000/60/EC a z existujúcich údajov o kvalite vody v databáze Slovenského hydrometeorologického ústavu. Vypracovaná metodika navrhuje konkrétne postupy na určovanie, napr. - vplyvu dĺžky obdobia na vývojové trendy; - spôsobov výpočtu štatistických ukazovateľov; - spôsobov identifikácie trendov rastu a poklesu, ako i bodov obratu trendu; - kritérií na rozhodovanie o významnosti jednotlivých trendov. Navrhnutá metodika bola aplikovaná pri analýze vybraných ukazovateľov kvality vody v mieste odberu Hron-Šalková , situovanom pri Banskej Bystrici. Z výsledkov vyplýva, že po prudkom náraste znečistenia stredného Hrona v sedemdesiatych rokoch dvadsiateho storočia dochádza k postupnému zlepšovaniu kvality povrchových vôd v tomto úseku.
The aim of the paper is to study spatial and temporal changes in the magnitude, duration and frequency of high flows in the Danube basin. A hydrological series of the mean daily discharges from 20 gauging stations (operated minimally since 1930) were used for the analysis of changes in the daily discharges. The high flow events were classified into three classes: high flow pulses, small floods, and large floods. For each year and for each class, the means of the peak discharges, the number and duration of events, and the rate of changes of the rising and falling limbs of the waves were determined. The long-term trends of the annual time series obtained were analyzed and statistically evaluated. The long-term high flow changes were found to be different in three individual high flow classes. The duration of the category of high flow pulses is decreasing at 19 stations on the Danube and is statistically significant at the Linz, Vienna, Bratislava and Orsova stations. The frequency of the high flow pulses is increasing in all 20 stations. Also, the rising and falling rates of the high flow pulse category are increasing at the majority of the stations. The long-term trends of the selected characteristics of the small floods are very similar to the trends of the high flow pulses, i.e., the duration of small floods is decreasing, and their mean number per year is increasing. In the category of large floods the changes were not proved.
In recent years the issue of the natural hydrological and meteorological time series fluctuation has been discussed more and more intensively. As the series of measured hydrological and climatological data become longer and easier worldwide accessible it is possible to deal with a large amount of historical data in their complexity. Handling these data we cannot go without new methods of mathematical statistics and mathematical analysis. In the study some methods of the long-term trends identification in the hydrological time series are presented. Apart from the classical methods, like that of moving averages, the paper focuses in detail on the Hodrick-Prescott (HP) filter. The HP filter is applicable to the trend analysis of the long-term hydrological time series. Next, a new method of the period length identification, the combined periodogramm method, is theoretically developed. Using this method the long cycles length identification becomes more precise. Here, the cycle is considered to be long when it takes the length of about 1/6 to 1/3 of the measured time series. Identification of such long cycles is important with respect to the future hydrospherical processes forecast. Results of application of these methods to the Slovak hydrological time series are presented in the second part of the study. and V posledných rokoch sa začína čoraz viac diskutovať na tému prirodzených fluktuácií hydrologických a meteorologických radov. So stále sa predlžujúcimi radmi meraných hydrologických a klimatických údajov a zlepšujúcim sa prístupom k meraným údajom na celom svete možno komplexnejšie spracovať veľký počet historicky nameraných časových radov. Pri spracovávaní týchto údajov sa nezaobídeme bez rozvoja nových metód štatistiky a matematickej analýzy. V predloženej štúdii boli opísané metódy identifikácie dlhodobého trendu hydrologických radov. Popri už klasických metódach (metóde kĺzavých priemerov) bol v tejto práci rozpracovaný Hodrickov-Prescottov (HP) filter. HP filter možno aplikovať na analýzu trendu dlhodobých ročných hydrologických časových radov. Ďalej bola v štúdii teoreticky rozpracovaná nová metóda identifikácie dĺžky periód časových radov - metóda kombinovaného periodogramu. Uvedená metóda spresňuje identifikáciu dĺžky dlhých cyklov, teda cyklov s dĺžkou okolo 1/6 až 1/3 meraného časového radu. Práve identifikácia týchto dlhých cyklov je veľmi dôležitá pri odhade budúceho vývoja hydrosféry. Praktické použitie uvedených metód na slovenských hydrologických radoch je prezentované v druhej časti štúdie.
The main objective of this study is to develop a model procedure for predicting low flows for a large set of gauged basins located in the Rhine-Meuse area. The methodology is primarily based on the analysis of recession curves, river discharges being essentially provided by groundwater flow during drought period. Our objective is to use recession coefficients in order to calibrate base flow predictions coming out from a groundwater reservoir. Problems related to the temporal variability of recession coefficients are discussed. We come to the conclusion that lows flows prediction can be improved by implementing a new groundwater reservoir into the RR model based on our knowledge of low flow processes. and Jednou z požiadaviek Rámcovej smernice o vode (WFD, 2000/60/EC) je analýza trendov a dlhodobá predpoveď vývoja znečistenia povrchových tokov. Pri odhade vývoja znečistenia toku je potrebné brať do úvahy nielen možné zdroje znečistenia, ale je potrebné uvažovať aj s vývojom množstva vody v tokoch a so zvyšovaním teploty tokov v dôsledku očakávanej klimatickej zmeny a zmeny vo využívaní vodných zdrojov. V príspevku je analyzovaný vývoj mesačných koncentrácií vybraných ukazovateľov kvality vody v toku Dunaja v stanici Bratislava (napr. Chl-a, Ca, EC, SO4 2-, Cl- , O2, BSK5, N-celk, PO4-P, NO3-N, NO2-N a pod.) za obdobie r. 1991-2005. Za účelom dlhodobej predpovede koncentrácií každého ukazovateľa kvality vody sme na základe štatistických testov vybrali najlepší autoregresný Box-Jenkinsov model s dvoma regresormi: 1. prietokmi a 2. teplotami vody. Scenáre pre mesačné prietoky a mesačné teploty vody boli vytvorené pre tri stavy: i) priemerné podmienky - medián prietokov a teploty vody; ii) nízke prietoky a vysoké teploty vody; a iii) vysoké prietoky a nízke teploty vody. Tieto scenárové podmienky boli vypočítané z denných údajov z obdobia 1931-2005 ako percentily (1. percentil, medián, 99. percentil). Použijúc tieto scenáre sme vybranými Box-Jenkinsovými modelmi s dvoma regresormi simulovali extrémne mesačné hodnoty vybraných ukazovateľom kvality vody v Dunaji pre extrémne hydrologické a teplotné podmienky.
The aim of the paper is to analyse a possible teleconnection of AO (Artic Oscillation), SO (Southern Oscillation), PDO (Pacific Decade Oscillation), NAO (North Atlantic Oscillation) and QBO (Quasi Biennial Oscillation) phenomena with long-term streamflow fluctuation in Hron River basin (Central Slovakia). The spectral analysis shows that for the series of AO, NAO, SO, and PDO indexes we can identify the ca 2.4-; 3.6-; 7.8-; 14-; 21-;30- and 36-yr cycles. The coincident cycles were found in the monthly discharge time series from the Hron basin (period 1931-2000) using combined periodogram method. As these periods were found in almost all discharge series analysed within very different geographical zones, it can be considered as the general regularity on the earth. The regularity is related to general oceanic and atmospheric circulation, part of which are also the SO, AO, PDO and NAO phenomena. and Cieľom predloženej štúdie je analýza možných telekonekcií Arktickej oscilácie (AO), Južnej oscilácie (SO), Tichomorskej dekádnej oscilácie (PDO), Severoatlantickej oscilácie (NAO) a Kvázi dvojročnej oscilácie (QBO) s viacročnými cyklami priemerných ročných prietokov v povodí rieky Hron (stredné Slovensko). Spektrálnou analýzou časových radov AO, NAO, SO, a PDO indexov boli nájdené nasledujúce viacročné cykly kolísania indexov: ca 2,4; 3,6; 7,8; 14; 21; 30 a 36 rokov. Metódou kombinovaného periodogramu boli nájdené zhodné cykly kolísania viacročných suchých a mokrých období i v mesačných prietokových radoch z povodia Hrona (1930-2000). Keďže tieto periódy boli nájdené vo všetkých prietokových radoch z rôznych geografických zón, môžu byť považované za všeobecný jav na Zemi. Toto pravidelné opakovanie mokrých a suchých období súvisí so všeobecnou cirkuláciou oceánov a atmosféry, súčasťou ktorých sú i SO, AO, PDO, NAO a QBO javy.