A SCREENING TOOL FOR DETERMINATION OF PROCESS IMPORTANCE ACROSS THE GROUNDWATER/SURFACE WATER INTERFACE

Identifying dominant and rate-limiting physical and biogeochemical processes in the context of contaminant mass transfer and transformation is critically important for estimating contaminant fluxes and compositional changes across the groundwater/surface water interface (GWSWI). A new, user-friendly, spreadsheet- and Visual Basic-based analytical screening tool that enables assessment of controlling processes across the GWSWI is presented. Based on contaminant properties, identified processes that may play a significant role in solute transport/transformation are evaluated in terms of a ratio of process importance (P_i) that relates the process rate to the rate of fluid transfer. P_i can also be related to the ratio of timescales of mass transfer/transformation processes to that of hydraulic exchange. The screening tool currently applies to various organics and inorganics of interest within the context of GWSWI. Application of the new screening tool is demonstrated through evaluation of important hydraulic and biogeochemical processes governing contaminant transport between groundwater and surface waters represented by both simple and complex hydraulic environments, including analysis of a canal exhibiting gaining and losing characteristics.