Disaggregation of Catchment Runoff Isotopic Data to Determine Water Source Ratios and Characteristics within the Snowy Mountain Range

Traditionally, separation of streamflow into its component parts, i.e. base flow, snow-water, surface water, and rain-water has relied upon mechanical separation of the hydrograph based on base flow amount prior to and post snowmelt. Generally a line between base flow amounts before and after snowmelt is constructed upon the hydrograph and utilized to quantify base flow during the snowmelt time period. Such an approach is entirely theoretical and cannot be relied solely upon to determine the respective contributions of base flow and snowmelt to stream runoff. Isotope data is one empirical method to check the oft-made assumption of hydrograph separation. Oxygen and hydrogen isotopes are naturally occurring and can be quantified via isotopic analysis. These isotopes can be utilized to separate streamflow into the individual source water ratios due to fractionation, a process wherein environmental conditions affect isotopic concentration resulting in distinct signals. This project utilizes biweekly sampling of streamflow at ten sites in the Snowy Mountain Range coupled with streamflow hydrograph data for each site in order to check the standard method of hydrograph separation widely employed. Furthermore, the project provides information about isotopic characteristics based upon environmental factors and the amount of fractionation of streamflow at each sampling site.