Definately depends on whats
in the water
Pure water is best evaporated at 1000000 degrees celc. under hard vacuum
If you have the salt of a precious amine of any kind present in the water, you definately want to stay below 60 degrees (or so), using hot air setting on the oven. Another viable option is to use a strong light source and a fan (HPS + fan has worked wonders in the past).
Regards
Bandil