Here is your answer:
Your answer is D Melted snow.
Reason:That's because when snow melts it creates water and when it melts in a ditch it creates a stream of water! Also its not Rivers because there are combined with streams its not altitude because that has something to do with the air and when it came down to rather C, or D I choose D because C increasing rainfall there has to be a certain amount of rainfall to create streams of water maybe huge storms.
Your answer is D.
Look at this picture:
