The following chart is my starting point to describe how hydrogeological exploration differs from groundwater exploration. In this case, groundwater is just a component in hydrogeology. Therefore by exploring groundwater means you will be only looking at the groundwater itself, eg: where its location, how it moves and where does it flow. Whereas by exploring hydrogeology suggests you will look beyond the water. There are other aspects directly or indirectly connected to the moving groundwater in the aquifer. You may also look at the processes that are driven by the groundwater setting.