Year Established: 2011 Start Date: 2011-03-01 End Date: 2013-02-28
Total Federal Funds: $14,974 Total Non-Federal Funds: $30,602
Principal Investigators: Alejandro Flores, Shawn Benner
Abstract: Measurements of the stable oxygen and hydrogen isotopes of water are a powerful and increasingly economical method for constraining components of the hydrologic cycle. In particular, measurements of 18O and 2H have proven useful in determining sources of meteoric water, average residence times in the small catchments, as well as separation of streamflow hydrographs into stormflow and baseflow components. Many of these hydrological applications of stable isotope geochemistry, however, are made difficult without an a priori understanding of the isotopic signature of meteoric water in the form of liquid (rain), solid (snow and ice), and occult (fog condensation) precipitation. Furthermore, it is a reasonable expectation that any seasonal variability in sources of meteoric moisture will be correspondingly reflected in the isotopic signature of precipitation. This is particularly true of locations in the interior of large landmasses where rainout and continental effects will result in an isotopic enrichment of waters relative to the Global Meteoric Water Line (GMWL), which was constructed through sampling of precipitation in coastal regions. Despite the importance of understanding the isotopic signature of precipitation establishing a so-called Local Meteoric Water Line (LMWL) and the increasing use of stable isotope geochemistry for hydrologic applications in the Treasure Valley area, a robust construction of a LMWL has yet to be performed in the Treasure Valley. In this USGS Section 104(b) proposal, we seek to establish the LMWL for the Treasure Valley, Idaho. We will collect event-based precipitation samples to be processed by a full-service analytical facility for analysis of hydrogen and oxygen stable isotopes in water operated by the Department of Geosciences at Boise State University. We will then perform a rigorous statistical analysis of collected and analyzed samples to establish the LMWL and test the significance of any departures from the GMWL and analyze the impact of seasonality on the isotopic signature of precipitation. The proposed work will leverage already collected samples and will directly benefit projects being conducted jointly by the Idaho Department of Water Resources and the USGS Water Science Center.