Water
How can I name the water that is under the ground (грунтовые воды) in English. And how about the river is under the ground?

Question

Answer

groundwater is the water under the ground.  Surface water is above the ground like rivers, lakes, springs, oceans.

Answer

Groundwater:Water flowing under the land surface.
... are located underground at depths too deep to be economically exploated for human.

Answer

Maybe groundwater and subterranean river.