Title

Recharge dynamics of a perched phreatic aquifer

Semester

Fall

Date of Graduation

1998

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Joseph J. Donovan.

Abstract

Numerous techniques were used to analyze recharge rates, timing, and mechanisms for a perched, phreatic aquifer. Recharge rates were estimated using fluid mass balance (FMB), integrated hydrograph separation (IHS), and innovative hydrograph manipulation techniques. Timing and mechanisms of recharge were analyzed using signal-processing and linear-system approaches. Hydrometeorologic and hydrologic data were collected for a 16-month period (4/97 to 8/98) using both manual and automated techniques. Precipitation totaled 135.6 cm and evapotranspiration (ET) calculated using the Penman-Monteith method totaled 107.5 cm. Recharge estimates from FMB ranged from 20.3% to 33.6%. Springflows were modeled using a stage-discharge cross-correlation method. Recharge estimates from IHS of these springflows ranged from 59.8% to 72.2% (significantly higher than FMB estimates).;Conventional well-stage hydrographs were corrected for spring discharge using cross-correlation relationships resulting in storage accumulation curves (SACs). Recharge estimates using SACs corresponded well to IHS estimates and ranged between 49.0% and 74.2%. These curves represent a potentially powerful technique for recharge estimation over short-scale intervals (days to weeks).;Modified storage accumulation curves (MSACs), based on the slope of the SAC, were used to analyze recharge timing and mechanisms. A linear groundwater system was identified relating precipitation to water-level fluctuations and four signal-processing techniques were used to develop kernel functions. These kernels revealed that a significant amount of recharge occurs on the same day as precipitation. They also showed that both macropore and matrix processes are at work in this system.

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