Fluorescence excitation emission matrix (EEM) are applied to characterize the dissolved organic matter (DOM) from waters in the Three Gorges Reservoir, sampled at near the highest water level 175 m for the first time and followed drawdown to the lowest water level 145 m respectively. The composition, distribution and source of the DOM in the Three Gorges Reservoir are investigated with impacted by 30 m water levels fluctuation, and the correlations between each fluorophore s intensity and environmental factors such as pH, DO (dissolved oxygen), DOC (dissolved organic carbon), ORP (oxidation- reduction potential) etc. are fitted. From the results, all the DOM s EEM from main streams in the Three Gorges Reservoir had four fluorescence peaks, attributed to protein-like, humic-like and fulvic-like respectively. During 175 m dry season, fluorescence intensities in EEMs increased from upstream to downstream, with the Dam section having the strongest intensity|comparatively, during 145 m wet season, the fluorescence intensities was obviously higher than those in dry season, impacted by terrestrial confluence along the bank of the Three Gorges Reservoir, and the strongest intensity occurred in the middle and upper reaches. A good correlation between environmental parameters and EEM Peaks was observed in dry season. On the contrary, only Peak A and DO has positive linear correlation during wet season. The present article revealed that the water quality in the Three Gorges Reservoir is mainly affected by the terrestrial confluence, with less impact by the 30 m water level fluctuation in reverse way to the Yangtze River s natural wet-dry law.

Key words: the Three Gorges Reservoir, water level fluctuation, dissolved organic matter, fluorescence excitation emission matrix