DETERMINATION OF AQUIFER PARAMETERS FROM WELL TIDES

An equation for the specific storage of an inland artesian aquifer of infinite extent is developed from a consideration of the tidal dilatation of an idealized well-aquifer system. It was found that for a particular tidal frequency the specific storage S//s is related to tidal water level and barometric pressure fluctuations. Two arbitrary numerical methods are devised for estimating barometric efficiency from aperiodic water level and barometric pressure fluctuations. If the specific storage and barometric efficiency are known, in situ values of porosity n and the matrix bulk modulus E//m can be calculated. Tidal water level fluctuations were recorded in three observation wells in Montgomery County, Virginia. Physically reasonable values of specific storage, barometric efficiency, porosity, and matrix bulk modulus were calculated, but the accuracy of these values is limited by the imprecise measurements of water level and barometric pressure and the possibility of leakage from imperfectly confined aquifers.