Hydrogen and oxygen isotopes provide powerful tools to investigate hydrologic processes because they are intrinsic to the water molecule and behave as conservative tracers. Phase changes such as evaporation and condensation cause predictable fractionations by favoring the lighter or heavier species, imparting distinctive isotopic "signatures" to different regional waters. These differences facilitate the investigation of transport and mixing processes that lead to a greater understanding of watershed dynamics.
Every year since 1995 the Washington University Stable Isotope Laboratory has generated more than 1,000 isotope analyses of streams, rivers, springs, groundwaters, and rainfall representing dozens of hydrologic sites in east-central Missouri. Together, these data constitute the most complete isotopic time series available for any region. Our analyses have enabled us to discover accurate predictive models for flash flood peak flows, spring geochemistry, groundwater residence times, and the daily concentrations of solutes in the lower Missouri River. Our data have defined the residence times of Missouri springs, elucidated the effects of urbanization on recharge, allowed an isotopic hydrograph separation study to be made of the deadly, terribly damaging May 2000 flash flood that made the town of Union a federal disaster area, and revealed the source of contaminating waters that impacted a spring.
Our interests in regional hydrology extend to the examination of historical records and maps to determine the effects of river enginering on flood severity, and on the effects of urban sprawl on karst landscapes, stream discharge, and shallow groundwaters. We resurrected quantitative scientific data collected by Lewis and Clark, resulting in recent publications on Missouri River hydrology and on Earth's magnetic field.
In addition to the ongoing projects listed below, the lab is available to Washington University graduate students who are interested in using stable isotopes to understand geologic and hydrologic systems. Undergraduates are also introduced to the laboratory and to stable isotope systematics in two classes taught by Dr. Criss, Stable Isotope Geochemistry and Hydrology. Students are expected to complete class projects and many involve analytical work in the lab. |
