Robert W. Ritzi (Advisor), David F. Dominic (Committee Member), David A. Schmidt (Committee Member)
Master of Science (MS)
Groundwater levels are expected to fluctuate with precipitation, rising when precipitation increases and falling when it decreases. However, observations often show that groundwater levels rise in months when precipitation has decreased from the previous month, or alternately, falls in months when precipitation has increased from the previous month. Such paradoxical behavior is documented in a 30-year record for a monitoring well in southwestern Ohio. This record was analyzed to evaluate the hypothesis that mass balance controls the change in groundwater level such that changes cannot be predicted solely from monthly changes in precipitation. Though precipitation may vary from one month to the next, if the amount of precipitation recharging a system is not proportional to the amount leaving, storage will fluctuate. This mass balance approach was applied to this single monitoring well. Recharge was estimated from existing records of precipitation utilizing three approaches: (1) potential evaporation (PET), (2) pan evaporation, and (3) Thornthwaite and Mather calculations. Each of these estimates was utilized in an interpretive numerical model meant to represent only the gross hydraulic aspects of the aquifer. Results showed that the mass balance was not sensitive to the method by which recharge was estimated. For the months December to January, approximately 46% of the instances show paradoxical rising head behavior for all three estimates of recharge. For the months January to February, 42% to 46% of the instances show paradoxical rising head behavior, depending on the method used to estimate recharge. These results strongly support the hypothesis that mass balance explains the paradoxical behavior in groundwater levels.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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