Background.

The Baetidae family (Ephemeroptera: Insecta) is abundant and diverse in freshwater ecosystems, especially in lotic systems: Although, information on these groups in Colombia is still scarce.

Goals.

The present study was directed to increase the taxonomical and ecological knowledge of Baetidae family in Alvarado river basin (Tolima, Colombia), evaluating the substrates; sand, gravel/cobble, rock and leaf litter, and determining the possible relationships with some physicochemical parameters.

Methods.

The collection was made with a Surber net in rapids and backwaters, in four substrates (sand, gravel/cobble, rock and leaf litter) additionally physicochemical parameters were evaluated.

Results.

A total 2386 individuals were collected, distributed in nine genera and 14 species. Baetodes sp. (23.93%), Camelobaetidius edmunsi (19.70%), Guajirolus queremba (12.70%) and Paracloeodes binodulus (11.32%) were the most abundant species in the basin. The highest density of organisms was found in sampling sites QLCA, QCHU, RACV and RACH. Rock was the preferred substrate for colonization and establishment of most species in all sites.

Conclusions.

The family Baetidae was related with type of substrate, as well as variables such as; pH, alkalinity, hardness, total solids, electrical conductivity, BOD5, dissolved oxygen, water flow and nitrates, which suggest a potential influence of anthropogenic effects on species establishment.