Stream ecology is the scientific study of the aquatic species, their interactions with one another, and their connection with the biological, chemical, and physical processes from multiple dimensions within streams. Streams display great variability in their force and generate spatial and temporal gradients in abiotic and biotic activities. The physical structure of stream networks show headwater systems behave different from mid-lower order systems with mean annual discharge, channel size, alluvial habitat and contributing area all key factors. Source: Wikipedia (en)