What would happen if the amount of fresh water entering mono lake decreased?

There's two things that will happen as a result of decreased fresh water income in the Mono Lake:

1. Salinity will increase; as the amount of freshwater will decrease, the Mono Lake will experience increase in salinity of its waters, which will be caused by the lower amount of incoming water and the big evaporation because of the high temperatures.

2. Dry out; the lake will eventually dry out, and that will be due to the bigger evaporation of its waters in comparison to the freshwater that's entering into it.