The SIF provides simultaneous analysis of ¹⁸Oand D/H isotope ratios in liquid water samples using a Laser Water Isotope Analyzer V2 (Los Gatos Research, Inc., Mountain View, CA, USA). For ¹⁸O and D/H at natural abundance, each sample is injected 6 times. The first 2 injections are discarded to eliminate memory effects and the average of injections #3-6 is used for isotope ratio calculations. For enriched samples, the number of injections is increased to 8 and the average of injections #5-8 is used for isotope ratio calculations.  Sample isotope ratios are standardized using a range of working standards that have been calibrated against IAEA standard reference materials (VSMOW, GISP, and SLAP).  Precision for water samples at natural abundance is typically ≤0.3 permil for ¹⁸O and ≤0.8 permil for D/H.  Final ¹⁸O/¹⁶O and D/H values are reported relative to VSMOW.