Hrvatske vode, Vol. 32 No. 128, 2024.
Professional paper
Hydrological analysis of minimum and maximum annual flows along the course of the Sava River in Croatia
Ognjen Bonacci
orcid.org/0000-0002-7123-3421
; Sveučilište u Splitu, Fakultet građevinarstva, arhitekture i geodezije, Split, Hrvatska
*
Tanja Roje-Bonacci
; Sveučilište u Splitu, Fakultet građevinarstva, arhitekture i geodezije, Split, Hrvatska
Duje Bonacci
; Sveučilište u Zagrebu, Fakultet hrvatskih studija, Zagreb, Hrvatska
* Corresponding author.
Abstract
The paper analyses all the available series of minimum and maximum annual flows calculated at 13 hydrological stations along the course of the Sava River in Croatia. Only official data of Croatian Meteorological and Hydrological Service (DHMZ) from Zagreb have been used. The lengths of the series are different, and observation breaks within certain series have been noticed. The last year included in the analysis is 2022. A decreasing trend of minimum annual flows has been observed at all hydrological stations. The values of linear regression coefficients indicate that the decline process behaves differently at each of the stations. It ranges from an average of 2.2 m3/10 years at the Rugvica station to an average of 7.4 m3/10 years at the Davor station. Analyses of the differences in the series of minimum annual flows between neighbouring hydrological stations show certain irregularities that indicate probable errors in the determination of minimum annual flows at some stations. These can be most probably explained by instability (erosion or backfilling) of the riverbed bottom and the insufficient number of measurements at low water levels, which causes constant changes in the lower parts of the flow curves. Regarding the series of maximum annual flows, an increasing trend has been observed at most stations, with some not indicating any trend. The highest increasing trend of 61 m3/10 years on average has been observed at the Podsused station. The decreasing trend of 14 m3/10 years on average has been measured only at the Županja station. The series of differences in maximum annual flows between the neighbouring stations greatly differ, which indicates insufficiently accurate measurements (determination) of maximum flows. This is probably consequential to insufficient number of flow measurements at high water levels and thus insufficient reliability of the determined flow curves in flooding areas.
Keywords
minimum annual flow; maximum annual flow; Mann-Kendall test; Sava River; Croatia
Hrčak ID:
326920
URI
Publication date:
2.7.2024.
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