TEMPERATURE VARIATIONS IN INTERMITTENTLY-PUMPED WELLS WITHIN UNCONFINED ALLUVIAL AQUIFERS

Temperature fluctuations in response to high-frequency intermittent pumping were observed from February 2014 to August 2016 in 14 wells in three shallow, unconfined, alluvial aquifers along the Ohio River. This study demonstrates 2-component temperature signals inside pumping wells varying between pump-on and pump-off periods. Both components vary seasonality at different magnitudes. While pump-off temperatures fluctuated up to 3.8^o C seasonally, short-term temperature shifts induced by turning the pump on were 0.2 to 2.5^o C. The short-term temperature shifts were highest in magnitude in summer and winter because groundwater lagged behind surface water temperature in average by six months for majority of the wells and ranged from 140 to 270 days. The short-term and seasonal temperature shifts were spatially and temporally complex. However, the short-term temperature shifts indicate that pumping always induce water with contrary temperature to that of groundwater. This result confirms that stream exfiltration is a major source of water budget to a number of these wells.