Modeling the influence of changes in barometric pressure on groundwater levels in wells

Abstract.

A physically based conceptual model for the influence of barometric pressure on groundwater wells was developed and tested in this study. It was proposed that water level fluctuations in response to barometric pressure are due in large part to the different manner in which the pressure is propagated through the water column in the well and the porous media outside the well. The loss in pressure head through the porous media causes a lateral hydraulic head gradient to be developed around the well-screen region, as well as a vertical one through the porous medium. The well-water flux across the screen and the consequent change in well-casing storage were appropriately linked with groundwater flow and estimated through an iteration technique. Results suggest that the physically based model in this study is effective in estimating the water level fluctuations in a well due to changes in barometric pressure. The magnitude and behavior of well response varies with the hydraulic properties (hydraulic conductivity and specific storage) and well geometry (casing radius, screened length, and depth of well). Therefore, the model relating the barograph and responding water levels can potentially serve as a tool for estimation of hydraulic parameters of the tested formation in the equivalent manner of slug tests. In conclusion, the influence of barometric pressure on groundwater wells is solved by relevant integration of three parts: i) the solution of the differential equation governing groundwater flow, ii) the estimation of well-water flux across the screen and changes in well-casing storage, and iii) use of the well screen as a boundary condition for coupling between i) and ii).