Water velocity, Artificial channels, Temperature, Argentina Pampean plain, Turbidity, Nutrients, Epipelic diatom assemblage, LOWLAND STREAM, PERIPHYTON, RESPONSES, COMMUNITY STRUCTURE, SUSPENDED SEDIMENT, EFFECT SIZE, CURRENT VELOCITY, LIMNOLOGY, WATER-QUALITY, RIVERS, GRADIENTS, Environmental quality, Amphibians, Analysis, Eutrophication