Abstract: Under barometric pressure(BP), groundwater flow in a well-aquifer system is a kind of hydromechanical coupling problem. Applying the flux boundary condition on borehole wall and water pressure equilibrium condition inside and outside the borehole wall under barometric pressure, an analytic solution to well water level changes is proposed in this paper. The formulation shows that the BP coefficients increase with time length and tend to BP constant. Change of BP coefficients over time length only depends on the ratio of transmissivity (T) to the well radius squared (r²_w), and has nothing to do with the changing process of BP. The BP constant only relates to aquifer loading efficiency (B), and has nothing to do with the aquifer transmissivity and well radius. The BP coefficients change over time in the analytic formulation is consistent to the analysis conclusions of the measured data from Nanxi wells. Based on the BP coefficient changes over time length, a parameter estimation method has been suggested and discussed in its application to the estimation of aquifer BP constant (or B) and transmissivity using Nanxi well data.

Key words: Well-water level, Barometric pressure, Analytic solution, Parameter estimation, Barometric pressure coefficient