Statically isolated conditions in the stratum–borehole hydrogeological system under consideration at periods of ≥ 3 h are established on the basis of the investigation of barometric and tidal responses of the water level in a borehole located in the territory of the Mikhnevo Geophysical Observatory, Institute of Geosphere Dynamics, Russian Academy of Sciences. The barometric effectiveness, tidal sensitivity of the water level, elastic parameters, and porosity of water-bearing rocks are estimated. A model of the inertial character of the water exchange in the stratum–borehole system is constructed depending on the period of variations with allowance for the borehole design, as well as the water transmissibility and elastic capacity of the aquifer. The results of modeling are in compliance with the dependence of the amplitude transfer function from variations in the atmospheric pressure to variations in the water level. The results of processing the data of high-precision measurements made it possible to refine the transmissibility of the aquifer obtained from the data of experimental filtration works.