What Am I

I run down the hills And over the rocks I still keep running With mother natures blocks You walk and run over me Each and every day It doesn't matter what you do I'm always here to stay I get knocked around All of the time The sun reflects off of me And makes me shine Sometimes I stop And turn dark brown Just to get used up By this sacred ground You need me to live Without me you would die I'm even so blessful I fall from the sky Water