A series of natural gradient tracer tests was conducted to delineate groundwater flow patterns near a drainage ditch in glacial outwash of central Wisconsin. Water level and precipitation data were collected to document factors that could contribute to temporal variations in the flow field. Year-to-year variations in recharge generated shifts in flow paths between replicate tracer experiments. The field data provided the basis for numerical modeling designed to elucidate the sensitivity of flow paths to variations in recharge. A three-dimensional aspect of flow paths identified in this study is a ''wrap-around'' pattern, in which groundwater passes under a surface water body prior to turning in the downstream direction and continuing to migrate as subsurface flow. This feature was suggested by the path of a tracer injected deep in the aquifer and was simulated at all recharge rates employed in the modeling. The three-dimensional nature of the flow field and temporal variability of flow paths can have important implications for design of monitoring networks near narrow surface water bodies. ¿ American Geophysical Union 1995