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We monitored the zooplankton community dynamics of a regulated river system (the Nakdong River) in South Korea, in an effort to characterize the relationship between basin rainfall quantity and changes in zooplankton community structure. The river studied herein has four multipurpose dams upstream and one estuarine barrage at the river mouth, resulting in intensive flow regulation. We hypothesized that flow regulation would effect zooplankton community structure changes not only within the summer period of concentrated rainfall, but also during the subsequent seasons. Field monitoring was conducted on a weekly basis (1999 to 2009) at the study site (27 km upstream from the estuary dam). The studied years were divided into two groups: rainy years with annual rainfall greater than total average annual rainfall, and dry years (years with lower than average annual rainfall). The zooplankton community data was also divided into two groups according to year and community structural characteristics. The summer density of zooplankton was low during the summer concentrated rainfall period. In the autumn, zooplankton density was statistically related to river flow (r 2 = 0.30, P < 0.05, N = 11), which was affected by the summer concentrated rainfall (r 2 = 0.31, P < 0.05, N = 11). Furthermore, autumn zooplankton density was positively related to that observed in the summer (r 2 = 0.53, P < 0.05, N = 11). Therefore, it can be concluded that summer concentrated rainfall can affect the following seasons' zooplankton densities caused by dam flow control, and the potential growth rate of zooplankton

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