Changes in streamflow of the Tigris and the Euphrates Rivers are shown to be associated with the North Atlantic Oscillation (NAO), a large-scale mode of natural climate variability which governs the path of Atlantic mid-latitude storm tracks and precipitation in the eastern Mediterranean. Composite indices of Turkish winter (December-March, DJFM) temperature and precipitation are developed which capture the interannual-decadal climate variability for the Tigris-Euphrates headwater region, a significant source of freshwater for Turkey, Syria and Iraq. These indices are significantly correlated with the NAG, with 27% of the variance in precipitation accounted for by this natural mechanism. As evidenced by the recent widespread drought events of 1984, 1989 and 1990, the Tigris-Euphrates streamflow also exhibits significant, similar to +/-40% variability, associated with extrema. Copyright (C) 2000 Royal Meteorological Society.
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