- Webb 1100
Title: Quantification of storm groundwater into streams using continuous 222Rn activity
Abstract: 222Rn has been used in hydrology as a naturally occurring tracer to identify groundwater intruding into a variety of systems such as near-shore marine environments, marshland environments, or lacustrine environments. This study aims to test 222Rn’s capacity to act as a conservative tracer within a stream environment through the creation of a series of storm hydrograph separations. Measurements of 222Rn activity were taken every 10 minutes during initial tests and every 15 minutes during secondary tests to create a high-resolution storm-water discharge dataset. The purpose of these hydrograph separations is to determine how much of the storm-water within a river is groundwater and how much is from precipitation or throughflow. This distinction is made possible by the difference in 222Rn activity between groundwater (1 to 100 Bq/L) and event water (0.001 to 0.01 Bq/L). The results of the 222Rn mixing relations will be compared to two existing methods of creating storm hydrographs: 1) ∂18O and ∂D stable isotope mixing relations, 2) dissolved SiO2 and SO4 mixing relations. The introduction of groundwater into the stream during a storm is expected to be directly related to amount of precipitation. More precipitation is expected to lead to loading of the phreatic surface resulting in an increased of groundwater flowing into the stream. The 222Rn measurements are expected to produce similar results to what is seen in the Stable Isotope and Dissolved Tracer methods.