ABSTRACT
From April to December 1996 a limnological study was carried out in 17 streams near Medellín, in order to stablish their water quality. The area is located in Piedras Blancas Park (6§8`20``N, 75§30`20``W)SE of Medellín at 2400m altitude. Three sampling periods, encompasing wet and dry season were selected. April-May, August-September and October-December. For qualitative collection methods hand screen and D-net were used. Each station was intensively sampled to collect most macroinvertebrates in all types of habitat. The area sampled in each station was 6m2. Physicochemical variables ingeneral showed small fluctuations along the study; only conductivity and total dissolved solids exhibited significant changes, all related with high precipitation in the west season. Macroinvertebrate community consisted of 113 genera, 63 families and seven phyla. Trichoptera was the most abundant group. The results indicate that the freshwater ecosystems in the study area present a high water quality corresponding to a oligo-metrophic system. Key words: Aquatic ecology, tropical limnology, tropical macroinvertebrates