Verification of the IHACRES hydrologic model in a foothill catchment in the Carpathian Foothills

Praca przedstawia wyniki kalibracji i weryfikacji modelu IHACRES na przykładzie zlewni pogórskiej. W pracy rozważane są również wybrane aspekty niepewności prognozowania przepływów. IHACRES jest koncepcyjnym modelem opad-odpływ o parametrach skupionych, wykorzystującym metodę hydrogramu jednostkowego. Danymi wejściowymi w modelu były serie czasowe opadu, przepływu i temperatury powietrza. Dokładność modelu została zweryfikowana na podstawie współczynnika dopasowania modelu i błędu bezwzględnego modelowania. Wyniki wykazały, iż model ma tendencję do niedoszacowania przepływów wezbraniowych i przeszacowania niskich przepływów; wielkość opadu efektywnego i jego rozkład w ciągu roku jest dobrze oszacowany; wydajność modelu jest nieco lepsza w okresie kalibracji, aniżeli w okresie weryfikacji; model stosunkowo dobrze szacuje średni przepływ i wezbrania o przepływie mniejszym niż 10 m3∙s-1.The study presents results of calibration and verification of the IHACRES hydrologic model in a foothill catchment. The study also discusses some aspects of uncertainty in streamflow predictions. IHACRES is a lumped conceptual rainfall-runoff model based on unit hydrograph principles. Time series of rainfall, streamflow and air temperature were used as input data to the model. The model efficiency coefficient and bias were used to verify the accuracy of the model. The results show that model: tends to underestimate peak flows and overestimate the low flows; the value of effective rainfall and its distribution throughout the year are well estimated; the model efficiency is slightly better in the calibration period than in the simulation period; the model relatively well estimates the mean streamflow and peak flows of less than 10 m3∙s-1

Dissolved oxygen and water temperature dynamics in lowland rivers over various timescales

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