Long-term evolution of the Lower Danube discharge and corresponding climate variations: solar signature imprint
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The possible changes in temperature and precipitation regime are expected to lead to changes in the water regime of rivers. In this study, we investigate the long-term evolution of Lower Danube discharge in connection to variations in the precipitation in the Upper-Middle and Lower Danube Basins. The analysis is given by using annual means data from four gauges along the river, on the Romanian territory, namely, Orsova, Ceatal, Sulina, and Sf. Gheorghe, and from 27 weather stations in the Danube Basin. The comparison of the average precipitation in the Upper and Middle Danube Basin, as calculated from the records of 17 weather stations, with the discharge at Orsova, at the entry in the Lower Danube segment, shows correlated interannual and multi-decadal variations. The variations in precipitation in the Lower Danube Basin, recorded at ten weather stations, show up to a certain degree in variations of the tributary rivers discharge and in the discharge difference between the upstream station Orsova and the downstream station Ceatal. The precipitation and discharge data from the two sub-basins have been examined from the viewpoint of multi-decadal variability associated with Atlantic variability and with solar variability at decadal and multi-decadal timescales. Significant variations at the two timescales have been found.
The study has been done in the frame of the project PNII-RU-TE 21/2011, COST Action ES1005-TOSCA, and COST Action ES1102-VALUE. We thank anonymous reviewers for constructive and helpful comments.
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