Photosynthesis matters to me

Photosynthesis matters to me because without photosynthesis the plants the produce the oxygen we breathe would be non existent and everything on earth that is alive would day without the air to breathe.

http://www.dailymotion.com/relevance/search/photosynthesis+animation/video/x7lh5m_photosynthesis-video-by-peter-weath_tech

This resource is helpful for me because it puts science in a very simple way so its easy to understand. It uses small animations to accurately display what happens during photosynthesis. Because it's short sweet and to the point it makes it easy to watch. Other videos that drag on longer than needed are usually boring and I lose interest quicker which in turn doesnt show me anything. Short and sweet is the way to go for educational animations.

Scientific curiosity

My question about the natural world is, in the mountains where there are huge waterfalls that have been flowing for years and years how did they start and how do they not run out if they just keep flowing for years on end. This question doesn't bug me so much when I'm in San Diego but I go camping or backpacking or whatever it always makes me wonder when I walk by a huge waterfall. I think that every couple of seconds hundreds of gallons of water go crashing out and falling a few stories into another body of water that never seems to fill up. How does the body of water catching the waterfall not overflow if it constantly has thousands of gallons of water poured into it. Its not like the water can just float back up to the top for another go so how does the cycle all work?