The purpose of this study was to apply a multi-metric model of Lentic Ecosystem Health Assessments (LEHA) for environmental impact assessments of Cheongpyung Reservoir during 2005-2006 and assessed the ecological model values. The ecosystem model of LEHA was composed of eleven metrics such as biological parameters (Bp), physical parameters (Pp), and chemical parameters (Cp), and determined the rank of ecological health by the criteria, The variables of Bp were metrics of % sensitive species (M2, NMS) and insectivore species (M5, % In), which decrease as the water quality degradates, and these metric values were low as 1.5% and 32.4%, respectively. In contrast, the proportions of tolerant species and omnivore species as the other Bp parameters were 43% and 62%, respectively, which indicate a degradation and disturbance of the ecosystem. Riparian vegetation coverage (M9, % Vc) as a variable of Pp, were higher in the 2nd than 1st survey, and decreased toward the dam site from the headwaters. This was due to a habitat simplification (modifications) by frequent bottom dredging of sand and rocks. The variables of Cp were two metrics of specific conductivity (M10, CI) as an indicator of ionic contents (cations and anions) and the Trophic State Index (TSI) based on chlorophyll-a (M11, TSICHL) as an indicator of trophic state. These metric values of Cp had high temporal variations, but low spatial variations on the main axis of the reservoir along with the ecological health of a good condition. The environmental impact assessments using the LEHA multi-metric model indicated that the model values of LEHA averaged 30.7 in 1st survey(fair - poor condition) vs. 28 in 2nd survey(poor condition), indicating a temporal variation of the ecological health. The model values of LEHA showed a minimum (28) in the lacustrine zone (S5) and ranged from 29 to 30 in the other locations sampled, indicating a low longitudinal variation. Overall, environmental impact assessments, based on LEHA model, suggest that chemical water quality conditions were in good, but biological conditions were disturbed due to habitat modifications by frequent dredgings in the system.