ANALYZING WATER-LEVEL TIME SERIES TO IDENTIFY AQUIFER TYPE

Aquifer type (confined, unconfined, or semiconfined) may be identified by drilling or performing pumping tests. Both methods are costly, involve complex field issues, and may yield inconclusive results. Earth tides are known to influence water levels in wells penetrating confined aquifers or unconfined thick, low-porosity aquifers. Water-level fluctuations in wells tapping unconfined aquifers are influenced by changes in barometric pressure. Time-series analyses of water-level fluctuations of the Arbuckle-Simpson aquifer were utilized in nine wells to identify aquifer type by evaluating the influence of earth tides and barometric pressure variations. The Arbuckle-Simpson is a thick (~1000 m) carbonate aquifer located in south-central Oklahoma. Two types of harmonic analyses were employed to determine aquifer type: 1) signal identification and 2) amplitude and phase angle determination. Based on the results, portions of the Arbuckle-Simpson aquifer responded as each type of aquifer. The results demonstrate that the method is an accurate and low-impact to determine aquifer type.