Strontium isotope systematics of base flow in Piedmont Province watersheds, Georgia (USA)

Base flow rates decreased by a factor of 2-3 during the summer months and this is accompanied by increased alkalinity concentrations. 87Sr/86Sr ratios, however, were temporally invariant for a given stream basin and were independent of season, antecedent rainfall, and discharge. 87Sr/86Sr ratios were unique for each of the 4 basins and a general trend toward higher ratios with increasing basin area was apparent. The inferred contribution from minerals with high Rb contents such as K feldspar and muscovite may have resulted from the greater integration of flow from mineralogically diverse pathways afforded by a larger basin area. The basin specificity and temporal or seasonal invariability make 87Sr/86Sr ratios an invaluable hydrological tracer that can be readily employed in mass balance studies of stream flow within the Piedmont Province.