Describe the characteristics of the water at the mountain source

Speed: fastness of water falling
Temperature: hotness of water
Oxygen Level: bubbles in water
Nutrient Level: water is a vital nutrient

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.

Answermost of the time it would be ground into fine sediment,and sometimes they are carried away from the original location;