UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 2:08
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Conference: Bucharest University Faculty of Physics 2004 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
Spatial and temporal variability of water resources in Romania


Authors:
Monica Ghioca


Affiliation:
National Institute of Hydrology and Water Management, Bucharest, Romania


E-mail


Keywords:
water resources,temporal variability, NAO


Abstract:
The study of climate variability is important for better understanding the hydrological processes that lead to drought periods in Romania. The main characteristics of spatial and temporal variability of the precipitation and streamflow have been studied using the long term monthly series (1931-2002) at 15 meteorological stations and 39 hydrometric stations. Pettitt test was applied to find possible trends and change points. Almost all stations emphasize a systematic decrease (“downward shift”) in precipitation and discharges data for 1981/1982 years.. The data have been filtered using empirical orthogonal functions (EOF) analysis which provides both principal modes of spatial variability and time coefficient series describing the dominant time variability. The first EOF explains the highest fraction of the total observed variance (56,7% for precipitation and 87,5% for discharges). The first EOF patterns show the same sign of variability over the entire country, meaning that a common large-scale process might be responsible for Romanian precipitation and discharges variability. The second EOF patterns show two regions with opposite signs of variability with east-west gradient. The physical reasons for this regional difference could be linked to the geographical characteristics such as orography. Explained variance of second EOF patterns of the precipitation is 5,9% (and 1,9 for discharges). Changes in precipitation and streamflow of Romanian rivers are shown to be associated with the North Atlantic Oscillation (NAO), a large-scale mode of natural climate variability. The drought periods, with reduced precipitation and discharges, are characterised by high index NAO.