Abstract: A quarterly investigation of the macrozoobenthos community in Yuqiao Reservoir was conducted during May 2010 to May 2011. A total of 51 macrozoobenthos species were found, among which, Insecta (23 species), Mollusca (15 species), Oligochaeta (12 species), and others (1 species) accounted for 45.1%, 29.4%, 23.5%, and 2.0% of the total, respectively. The dominant species were Glyptotendipes lobiferus, Cipangopaludina cathayensis, Limnodrilus hoffmeisteri, and L. claparedeianus.The average annual density and biomass of macrozoobenthos were 159.58 ind·m^-2 and 3.31 g·m^-2, respectively. The macrozoobenthos had the highest density in spring, followed by in winter and autumn, and in summer, and had the highest biomass in winter, followed by in summer and spring, and in autumn. The evaluation with Goodnight biotic index (GBI), ShannonWiener diversity index (H′), Margalef richness index (d), biological pollution index (BPI), familylevel biotic index (FBI), and integrated pollution index (BI) indicated that the overall water quality of the Reservoir was in slightmoderate pollution (Ⅱ-Ⅲ). As compared to that in 1999-2000 (Ⅲ), the water quality of Yuqiao Reservoir was somewhat improved.

Key words: δ_D, δ¹⁸O, meteoric water line, excess deuterium (d value), water vapor source, Xiaolangdi Reservoir area, eastern monsoon region.