Regional groundwater flow in deep aquifers adds advective components to the surface heat flow over extensive areas within the Great Plains province. The regional groundwater flow is driven by topographically controlled piezometric surfaces for confined aquifers that recharge either at high elevations on the western edge of the province or from subcrop contacts. The aquifers discharge at lower elevations to the east. The assymetrical geometry for the Denver and Kennedy Basins is such that the surface areas of aquifer recharge are small compared to the areas of discharge. Consequently, positive advective heat flow occurs over most of the province. The advective component of heat flow in the Denver Basin is on the order of 15 mW m -2 along a zone about 50 km wide that parallels the structure contours of the Dakota aquifer on the eastern margin of the Basin. The advective component of heat flow in the Kennedy Basin is on the order of 20 mW m -2 and occurs over an extensive area that coincides with the discharge areas of the Madison (Mississippian) and Dakota (Cretaceous) aquifers. Groundwater flow in Paleozoic and Mesozoic aquifers in the Williston Basin causes thermal anomalies that are seen in geothermal gradient data and in oil well temperature data. The pervasive nature of advective heat flow components in the Great Plains tends to mask the heat flow structure of the crust, and only heat flow data from holes drilled into the crystalline basement can be used for tectonic heat flow studies.