Under what conditions might a stream's volume increase, and under what conditions might it decrease? How would the size of the sediment particles in the stream's load differ in the two situations?.

The volume of the stream would increase when it was raining and would decrease when there hadn't been rain, not necessarily a drought but just no rain for a while. As far as the sediment particles part they would be slightly bigger because there would be less water for them to mix into causing them to join together.