New Insights from Well Responses to Fluctuations in Barometric Pressure

Abstract

Hydrologists have long recognized that changes in barometric pressure can produce changes in water levels in wells. The barometric response function (BRF) has proven to be an effective means to characterize this relationship; we show here how it can also be utilized to glean valuable insights into semi-confined aquifer systems. The form of the BRF indicates the degree of aquifer confinement, while a comparison of BRFs between wells sheds light on hydrostratigraphic continuity. A new approach for estimating hydraulic properties of aquitards from BRFs has been developed and verified. The BRF is not an invariant characteristic of a well; in unconfined or semi-confined aquifers, it can change with conditions in the vadose zone. Field data from a long-term research site demonstrate the hydrostratigraphic insights that can be gained from monitoring water levels and barometric pressure. Such insights should be of value for a wide range of practical applications.

Borehole water level response to barometric pressure as an indicator of aquifer vulnerability

“…Estimation of the barometric response function is improved by prior removal of Earth and ocean tides for which time domain methods [Rasmussen and Crawford, 1997;Rasmussen and Mote, 2007;Toll and Rasmussen, 2007] and frequency domain methods [Rojstaczer, 1988;Galloway and Rojstaczer, 1988;Rojstaczer and Riley, 1990] have been developed. To date, little attention has been given to the impact of interference from recharge and many locations have been chosen in part for their lack of recharge signal [e.g., Galloway and Rojstaczer, 1988;Rojstaczer and Riley, 1990;Quilty and Roeloffs, 1991;Beavan et al, 1991;Evans et al, 1991] while other authors have restricted their analysis to selected time periods where such interference is minimal or where effects can corrected by simple linear trend removal [e.g., Butler et al, 2011].…”

“…[5] A number of analytical models for predicting borehole water level response to barometric pressure have been developed for semiconfined aquifers both in the time domain [Butler et al, 2011] and in the frequency domain [Hsieh et al, 1987;Rojstazcer, 1988;Evans et al, 1991;Ritizi et al, 1991]. These models have been used to estimate confining layer and aquifer properties from barometric response functions for a variety of porous media and fractured aquifers [Rojstaczer, 1988;Galloway and Rojstacer, 1988;Rojstaczer and Riley, 1990;Quilty and Roeloffs, 1991;Evans et al, 1991;Beavan et al, 1991;Ackworth and Brain, 2008;Butler et al, 2011].…”

“…System properties including the vertical diffusivities (unsaturated zone pneumatic diffusivity and saturated zone hydraulic diffusivity) can be estimated from barometric response functions by fitting to an appropriate model [e.g., Weeks, 1979;Rojstaczer, 1988;Evans et al, 1991;Butler et al, 2011].…”

“…It is here suggested that vertical diffusivity (ratio of conductivity to specific storage) of the confining layer, derived from barometric response functions, can be used to characterize the potential for contaminant transport through the confining layer to the aquifer, providing a potential link with intrinsic groundwater vulnerability. The link between barometric response functions and aquifer vulnerability has been tentatively suggested in the past [Rojstaczer, 1988;Landmeyer, 1996] while others have used barometric response functions to distinguish between confined, unconfined, well skin and combined responses [e.g., Rasmussen and Crawford, 1997;Spane, 2002] and to assess the degree of confinement [e.g., Butler et al, 2011]. To the authors' knowledge, however, application of these techniques as an aid to quantifying aquifer vulnerability has not yet been demonstrated.…”

Groundwater surface water interactions and the role of phreatophytes in identifying recharge zones

“…These wells represent all WIZARD wells that were measured during the recovery period after the cones of depression have recovered from yearly irrigation and before winter pre-irrigation for the next year occurs . Fluctuations in water level elevation caused by barometric pressure on the order of fractions of meters (Butler Jr. et al, 2011) were not specifically addressed, since the drawdown created by pumping over the 40 yr study period is on the order of 10s of meters. The raster calculator in ArcGIS was used to create a depth to water raster by subtracting the water table elevation from the surface elevation provided by the DEM.…”