An Improved Method for Determining Barometric Efficiency

The barometric efficiency (BE) is the ratio of water-level changes in a well to the changes in barometric pressure that produces them. An estimate of barometric efficiency is needed to remove the atmospheric pressure effects on groundwater fluctuation to be able to analyze the influence of other stresses such as earth tides or groundwater pumping tests. The BE is currently determined by the Clark method. This research examines the Clark method as applied to water level fluctuations of several wells in the Arbuckle- Simpson aquifer located in south-central Oklahoma. The study was consistent with previous researchers findings in that the Clark method is inconsistent in the values that it produces and may overestimate the BE . In at least two instances, the Clark method produced physically unrealistic BE values greater than 100 percent. An improved method to determine the BE is presented which overcomes the deficiencies in the Clark method. The new model is tested using water level fluctuation data in two wells collected over a one year period to evaluate the consistency of the new method in a single well. Additional data was evaluated from three other wells to evaluate consistency across the aquifer. The new model demonstrates a consistent, realistic set of values that did not produce BE values exceeding 100 percent.