Characterizing Soil and Stable Water Isotopes Along the American River in Northern California, USA

A quantitative fractionation model of stable isotopes in meteoric waters exists however the same relationship is poorly understood in stable isotopic values of pore waters, meteoric waters, surface waters, and organic matter waters. A representative model for isotopic values will increase our understanding of current and past climate change in our local environment. This research focuses on the relationship between sediment porosity, composition, and grain size along the American River and surface and pore water stable isotopes.

To begin to quantify the relationship between different hydrologic regimes, the American River in northern California is used as a case study. In sediment sampling along the American River, characterization and isotopic fingerprints can further understand the systematics of this local river. The American River consists of three forks: North Fork (85 mi), Middle Fork (65 mi), and South Fork (90 mi) which originate from the Tahoe and El Dorado National forests. The American River watershed discharges an average of 3685 cu ft/sec over a total area of 1900 mi² . Five sampling locations of increasing elevation along each fork are chosen. A coring device is used to collect 12 inch sediment samples from these locations and preserved for manual inspection. Characterization of the sediment is determined by use of the Munsell soil chart and geologic description from maps. Presentation of these sample characteristics are provided with preliminary findings.