The fields of both geology and hydrology are very relevant today and into future. Most of my career as a hydrologist with the US Forest Service was both challenging and enjoyable. And the complexities of how stream type changes with geology, landforms, sediment, etc. offers many opportunities to consider and evaluate issues. The need to identify movement and supply ample quality sources of groundwater is not going away. Water law can be interesting. In my opinion, it’s a wise choice if you don’t mind some hard work at times. I loved it.
A Hydrogeologist may become a consultant on areas to do with slope stability and engineering geology...wrt issues like land subsidence.
Flood control models and highway engineering ate some of the areas where the input of a Hydrogeologist comes in,outside classroom work.
In urban planning for big towns ,the input of a Hydrogeologist is of immense significance.
Food security is also an area where a hydrogeologist may be of immense practical value outside of classroom academia. Large scale irrigation planning proposed for groundwater use may also employ the inputs of a hydrogeologist,thereby promoting cash crop farming and enhancing food security.
In mining exploration the inputs of a hydrogeologist would also be of immense help