Answer 1: That depends on the temperature of the water, the temperature and humidity of the air, and how finely the water is dispersed as it flows from the fountain.
Answer 2:In a very humid environment, the water does not evaporate very fast at all.
It certainly is dependent upon a lot of factors though, some of which are :
- Temperature of water
- Temperature of air
- Size and water-flow of/in the fountain
- Composition of water (Water in a fountain is seldom pure).
- Pressure of air.
- Humidity in the air.
- Radiated heat (or other forms of energy) from sun or other sources.
Without knowing all the factors, there is no way to give an answer 100% valid for this question.
A tiny indoor fountain with a total of 6 litres of water may evaporate 1 litre a day. If it is very dry indoor, then maybe up to 3 litres a day.