How does control water operate if there is a limited volume of water to work with? Create Water is a lower level spell but Control Water doesn't say anything in particular about creating water.
The spell starts with this sentence:
Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side.
All of the effects the spell list reference "the water in an area". Just as it says, the spell allows you to control the water in an area you choose. It won't create water, it will only control existing water.