Ground water reservoirs are commonly used in this country for storing 200m3 to 2000m3 water capacities when the area needed water supply having an elevated area (which elevation is sufficient for the head required) and this reservoir can be built on this. In Sri Lanka ground reservoirs are designed as per BS8007 and this design does not cover for earthquakes. However, it seems that no detail investigation has been carried out for response of these ground reservoirs for dynamic loads such as earthquakes. This research work concentrates on detail dynamic analysis of existing cylindrical ground reservoirs. The results reflect that existing cylindrical ground reservoirs are not sufficiently adequate to withstand even minor earthquakes. This implies that they must be analyzed for earthquakes since their natural period of vibration give high response for earthquakes which could even trigger structural failure.
