Nope, Its a closed loop cooling solution :]
Its kinda half way between air and water, but keep in mind its NOT a replacement for a high-end air cooler (NH-D14/SilverArrow) nor is it a replacement for a water cooling setup.
The water on H70 and H50 units never has to be changed.
An H70 will most likely not get you to 4.0Ghz with the most comfortable temperatures.
Hope this helped!
Pump+Rad+fans+Liquid is not kinda half way.. it's small scale liquid cooling that simple.