TEMPORAL VARIABILITY OF MAJOR ION CHEMISTRY OF SURFACE WATER AND GROUNDWATER IN ORISKANY CREEK, CLINTON, NEW YORK

The connection between Oriskany Creek and an adjacent shallow alluvial aquifer has been previously studied using environmental tracers, discharge measurements, and numerical modeling. Each study used water chemistry or discharge parameters measured at an instant or over the course of several hours. In our study, we sampled stream water and shallow groundwater daily for nearly one year and analyzed the samples for major ions using ion chromatography. Our goal was to examine daily variability of major ion content to determine if groundwater chemistry was affected by stream chemistry over time periods that ranged from days to weeks. Our results indicate that stream chemistry is affected differently by precipitation events during different seasons. For example, nitrate concentrations in the stream decreased after precipitation events before April. After this time, when agricultural fields are planted, precipitation events were correlated with an increase in nitrate concentrations in the stream from runoff. Late in the spring and through the summer, nitrate concentrations decreased after precipitation events. Sulfate concentrations increased during the spring and summer, perhaps as a result of an increasing percentage of groundwater as a percentage of stream discharge. Groundwater chemistry does not appear to closely track surface water chemistry. Instead, it is affected by other factors such as groundwater flow from upgradient areas or from recharge events that mobilize ions in the soil zone. The lack of correlation between stream and groundwater chemistry may affect the conclusions drawn in the earlier studies.