Interactions of the water table with the land surface impact a wide range of hydrologic, climatic, ecologic, and geomorphologic processes. Yet the factors controlling these interactions are still poorly understood. In this work, a new 2-D (cross-sectional) analytical groundwater flow solution is used to derive a dimensionless criterion that expresses the conditions under which the water table “outcrops” (i.e., reaches the land surface). The criterion gives insights into the functional relationships between geology, topography, climate, and resulting water table outcrops. This sheds light on the debate about the topographic control of groundwater flow, as the effective role of the topography is to constrain the water table only where it outcrops. The criterion provides a practical tool to predict water table outcrops if physical parameters are known and to estimate physical parameters if on the contrary water table outcrops are known. The latter aspect is demonstrated through an application example.