Ambient air quality monitoring was carried out in the vicinity of dam and nearby residential sites in four river basins in Karnataka with reference to SPM, RSPM, SO2 and NOx, employing Envirotech APM-460 Respirable Dust Sampler with provision to keep impingers having absorbing reagent. Further, three different methods of Air quality index (AQI) calculation on based on SPM and RSPM values were used to evaluate the prevailed ambient air quality in the near and surroundings areas at the time of dam constructional activities.