Dams and reservoirs provide many benefits but require careful geological investigation and design. Dams are typically classified by their design as gravity, arch, buttress or embankment dams. Proper site selection is important, considering factors like foundation stability and permeability. Past dam failures show the importance of understanding rock structures, weathering, and seismic activity. Reservoirs are categorized as storage, flood control or distribution based on their purpose. Geological studies of reservoir areas examine topography, groundwater conditions, permeability, and rock stability to ensure safe water storage and minimize leakage or sedimentation over time.