Ground Water-Surface Water Interaction and U Isotopes

²³⁴U/²³⁸U activity ratios used in conjunction with uranium concentrations have been applied successfully to river systems to trace sources of water.  We can calculate the relative contributions of tributary waters to the main stem river, estimate groundwater discharge to surface water flow, and estimate the relative abundance of different groundwater sources in major springs.  Our results thus far suggest that climate and lithology of a river’s drainage basin are the primary parameters that control the ²³⁴U/²³⁸U activity ratio and uranium concentration in river water..An understanding of a river’s base flow contribution, a crucial parameter in understanding  drought, is critical information for water policy managers.