<> "The repository administrator has not yet configured an RDF license."^^ . <> . . . "A Graphical Method for Estimation of\r\nBarometric Efficiency from Continuous Data—\r\nConcepts and Application to a Site in the Piedmont,\r\nAir Force Plant 6, Marietta, Georgia"^^ . "A graphical method that uses continuous water-level and\r\nbarometric-pressure data was developed to estimate barometric\r\nefficiency. A plot of nearly continuous water level (on the\r\ny-axis), as a function of nearly continuous barometric pressure\r\n(on the x-axis), will plot as a line curved into a series of\r\nconnected elliptical loops. Each loop represents a barometricpressure\r\nfluctuation. The negative of the slope of the major\r\naxis of an elliptical loop will be the ratio of water-level change\r\nto barometric-pressure change, which is the sum of the\r\nbarometric efficiency plus the error.\r\nThe negative of the slope of the preferred orientation\r\nof many elliptical loops is an estimate of the barometric\r\nefficiency. The slope of the preferred orientation of many\r\nelliptical loops is approximately the median of the slopes of\r\nthe major axes of the elliptical loops. If water-level change\r\nthat is not caused by barometric-pressure change does not\r\ncorrelate with barometric-pressure change, the probability\r\nthat the error will be greater than zero will be the same as\r\nthe probability that it will be less than zero. As a result, the\r\nnegative of the median of the slopes for many loops will be\r\nclose to the barometric efficiency.\r\nThe graphical method provided a rapid assessment of\r\nwhether a well was affected by barometric-pressure change\r\nand also provided a rapid estimate of barometric efficiency.\r\nThe graphical method was used to assess which wells at Air\r\nForce Plant 6, Marietta, Georgia, had water levels affected by\r\nbarometric-pressure changes during a 2003 constant-discharge\r\naquifer test. The graphical method was also used to estimate\r\nbarometric efficiency. Barometric-efficiency estimates from\r\nthe graphical method were compared to those of four other\r\nmethods: average of ratios, median of ratios, Clark, and\r\nslope. The two methods (the graphical and median-of-ratios\r\nmethods) that used the median values of water-level change\r\ndivided by barometric-pressure change appeared to be most\r\nresistant to error caused by barometric-pressure-independent\r\nwater-level change. The graphical method was particularly\r\nresistant to large amounts of barometric-pressure-independent\r\nwater-level change, having an average and standard deviation\r\nof error for control wells that was less than one-quarter that of\r\nthe other four methods.\r\nWhen using the graphical method, it is advisable that more\r\nthan one person select the slope or that the same person fits the\r\nsame data several times to minimize the effect of subjectivity.\r\nAlso, a long study period should be used (at least 60 days)\r\nto ensure that loops affected by large amounts of barometricpressure-independent\r\nwater-level change do not significantly\r\ncontribute to error in the barometric-efficiency estimate."^^ . "2007-07" . . "USGS"^^ . . . . . . "Gerard J."^^ . "Gonthier"^^ . "Gerard J. Gonthier"^^ . . . . . "HTML Summary of #2088 \n\nA Graphical Method for Estimation of \nBarometric Efficiency from Continuous Data— \nConcepts and Application to a Site in the Piedmont, \nAir Force Plant 6, Marietta, Georgia\n\n" . "text/html" . . . "Other-additional study" . . . "General about inducing technology types" . .