Ecology of a high Andean stream, Rio Itambi, Otavalo, Ecuador

A high Andean stream in the equatorial zone of Ecuador, the Rio Itambi, located at 2,600 to 4,600 m a.s.l., was studied to describe its physical structure, geomorphology, water chemistry and biodiversity.The Itambi catchment basin is characterized in its upper part by the volcanic sierra with >70% slope, and in its lower part by lake deposits. The length of Rio Itambi is 17 km with a catchment basin of 11,271 ha; the annual flow amounts to 0.07-0.5 m³/s. Stream structure is evaluated using a modification of the German “Geomorphological Structure Classification Method” with six main parameters (development of stream bed, longitudinal profile, transversal profile, bed structure, stream bank structure, and surrounding environment). Nowadays an impact of Rio Itambi's stream structure occurs due to anthropogenic activities. The water quality of Rio Itambi is presented on the basis of a monthly monitoring, and a comparison of rainy and dry season is given. An impact on quality is caused by human activities (sewage input, cattle raising), by landslides with a remodelling of the stream bed and by a low oxygen concentration due to altitude.Flora of stream banks as well as diatoms, macrophytes and fauna of stream bed were determined, and within the stream, biodiversity is low. In the upper part of the stream, this seems to be an effect of low oxygen saturation values and of landslide that remodel the stream bed, and in the lower part of the stream it is due to anthropogenic damage by sewage input.