I'm no expert, but I would think that on a GM's call, a hydromancer could roll to overcome (some) of the grounding effect of running water.
Also, a non lethal evocation of running water under the feet of another caster would be cool.
In fact, if you were a sneaky hydromancer, you could do a cheap running water effect for one shift over a large area, invest a few shifts into its duration, and then you would effectively be the only evocator who could lay down the magical hurt.
That would be nasty.