Isotopic Signatures of Precipitation and Streams along the North Shore of Lake Superior

Abstract

Lake Superior is the largest of the Great Lakes. Its size impacts precipitation along the North and South Shores, but the magnitude of its effects on the North Shore are unknown. Using stable isotopes of δ2H and δ18O to understand the source and transport of precipitation allows us to develop a deeper understanding of the hydrologic cycle in the region and the possible impact of the lake on precipitation. Samples were collected from five snow storms from November 2017 to March 2018, snowmelt from April 2018, and streamflow from May to August 2018. To further examine the hydrologic cycle along the North Shore, the Lester River watershed was studied for spatial and temporal variations from May to December 2018. This watershed, like many others along the North Shore, is a designated trout stream. Water samples collected from the stream and from precipitation were used to show seasonal trends and spatial variability across the watershed. This information highlights the timing of different processes in the watershed such as evaporation. Temperature data was also collected throughout the watershed to show conditions for trout and provide more information on hydrologic processes.