An idea: modern triple oxygen isotope constraints on lake mass-balance in Big Pine Island Lake, Michigan

Quantifying evaporation, water flow, and storage is essential to hydrologic management and paleoclimate studies, yet direct measurements are often impractical. In this project, we apply a water isotope-based mass-balance framework to constrain evaporation and flow of Big Pine Island Lake, a small inland lake in west Michigan experiencing water-level variability. Stable isotopes of water serve as natural tracers because isotopes fractionate during evaporation, and established isotope mass-balance models (e.g., Criss 1999) allow hydrologic parameters to be estimated without measuring inflow or outflow directly. In particular, we explore the additional information provided by the rare17O isotope, which is especially sensitive to evaporation and can thereby improve constraints beyond traditional δ18O and δD measurements. Such modern data are also critical for better calibrating signals of evaporation, groundwater input, and water balance recorded by sedimentary materials.

We report seasonal measurements of hydrogen and triple oxygen isotopes (δ18O, Δ′17O, and δD) from precipitation, groundwater, and surface waters of Big Pine Island Lake. Samples were measured using a Picarro L2140-i in the Water Isotope Lab at Grand Valley State University. These data were incorporated into mass-balance models following established approaches for inland lakes to quantify evaporation and residence time. This study provides a practical framework for assessing lake hydrology and informing water budget decisions where other measurements are limited. More broadly, it strengthens linkage between sedimentary proxy signals and the underlying hydrologic processes they reflect.