Final answer:
Groundwater flow can change from flowing down with the gradient to flowing against the gradient due to geological features or human activities such as pumping water from wells.
Step-by-step explanation:
Groundwater flow can change from flowing down with the gradient to flowing against the gradient under certain conditions. One factor that can cause this change is the presence of an impermeable layer of rock or soil. When groundwater encounters this impermeable layer, it is forced to change direction and flow against the gradient.
Another factor that can cause a change in groundwater flow is the pumping of groundwater from wells. If large amounts of groundwater are pumped from a well, it can create a cone of depression in the water table. This can cause groundwater to flow towards the well, even if it is against the natural gradient.