Alluvial aquifers are the most productive and widely used groundwater source for drinking water in Iowa. They are also the most vulnerable to contamination due to their shallow water table, hydraulic interchange with streams, and the potential for flooding. The Ames aquifer in Ames, Iowa is such an aquifer that is potentially vulnerable to contamination. The hypothesis that human enteric viruses enter the Ames aquifer from the South Skunk River and are transported to the municipal well field that supplies the Ames drinking water will be tested by analyzing river water and groundwater in piezometers and wells for viruses and stable isotopes along a groundwater flow path. The results will provide unique information about the extent and temporal variability of human enteric viruses in drinking water and demonstrate an innovative method (i.e., presence of viruses) to assess Groundwater under the Direct Influence of Surface Water (GWUDISW) in alluvial aquifers.