**Abstract**

Algal communities are robust indicators of the effect and impact of environmental flows on river-dependent ecosystems as they deflect directly and indirectly those physical chemical and biological changes induced by environmental flows, which alter nutrient concentration, salinity, and alkalinity. Algal periphyton communities are the deterministic indicators of many aspects of ecological disturbance and its response, providing valuable evidential data at intertemporal scale of riverine status in terms of both health and quality, and their collection is comparatively simple, inexpensive, and environmental friendly.

**Keywords:** biological indices, algae, rivers, biological monitoring, ecological assessment
