The impact of floodplain hydrology on the in-stream dissolved oxygen dynamics and the relation between dissolved oxygen and water temperature are investigated. This has been done by examining the time series of dissolved oxygen and water temperature coupled with meteorological and hydrological data obtained from two lowland rivers having contrasting hydrological settings. Spectral analysis of long-term oxygen variations in a vegetated river revealed a distinct scaling regime with slope ‘-1’ indicating a self-similar behaviour. Identical slopes were obtained for water temperature and water level. The same power-law behaviour was observed for an unvegetated river at small timescales revealing the underlying scaling behaviour of dissolved oxygen regime for different types of rivers and over various time scales. The results have shown that the oxygenation of a vegetated river is strongly related to its thermal regime and flow conditions. Moreover, analysis of short-term fluctuations in the unvegetated river demonstrated that physical factors such as rainfall and backwaters play a substantial role in the functioning of this ecosystem. Finally, the results show that the relation between water temperature and dissolved oxygen concentration at the diurnal timescale exhibits a looping behaviour on the variable plot. The findings of this study provide an insight into the sensitivity of rivers to changing hydro-physical conditions and can be useful in the assessment of environmental variability.
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.