Freestone River

A river type commonly occurring in mountainous areas whose sources of water include snowmelt and a series of coalescing springs and tributaries. The benthic zone is strewn with smooth rocks, boulders, gravel and sand. Few species of macrophytes can live there due to the steep gradients and swift currents. Macro invertebrate communities typically form food webs, and productivity is modest compared to limestone streams, due to the slightly acidic pH of the water.

Links
  http://www.freestone.com/
http://www.flyanglersonline.com/features/greatrivers/ausableny/