ASSESSING EMPIRICAL RELATIONSHIPS BETWEEN STORM CHARACTERISTICS AND EPISODIC GROUNDWATER RECHARGE USING LONG-TERM CLIMATE AND WATER-LEVEL RECORDS

Using long term, high resolution water table fluctuation data and precipitation records, we have developed a better understanding of the relationships between episodic groundwater recharge and precipitation characteristics in North Carolina. Using the Episodic Master Recharge (EMR) adaptation of the Water Table Fluctuation (WTF) method (Nimmo and Mitchell, 2014), we estimated groundwater recharge and precipitation characteristics for every significant precipitation event at ten locations in North Carolina over periods of twelve to thirty-five years. Recharge to precipitation ratios (RPR) were calculated for each storm event and associated with maximum intensity of precipitation, average intensity of precipitation, duration of precipitation, precipitation recurrence interval, and total depth of precipitation. Precipitation duration has a positive correlation with RPR, while precipitation intensity is negatively correlated with RPR. The relationship between total depth of precipitation and RPR is weak and location dependent, and precipitation recurrence interval shows no discernible correlation. RPR is substantially higher during the winter than it is during the summer, an effect which is magnified in the interior of the state. These relationships may inform climate models for predicting groundwater response to dynamic climactic conditions.