Objective:

The purpose of this article is to qualify the conditions of the Cesar river stream in the area of influence of the dumping of the STAR of the municipality of Valledupar, and its relationship with the biological indicators of contamination and BMWP/ Col quality index.

Methodology:

Four sampling stations were established on the Cesar River: E1 and E2 located upstream of the mixture zone at the municipal wastewater discharge point, E3 located at the point of mixing of the discharge and the river; and E4 located downstream of the discharge, letting know its physicochemical characteristics and to determine the biological conditions of the stream according to the BMWP/Col index for each of the established stations.

Results:

In stations E1 and E2, macroinvertebrates indicators of clean and well-oxygenated waters were obtained, with an acceptable water classification; while the stations E3 and E4, were found macroin-vertebrates indicators of contaminated waters of doubtful quality; E4 has being the most critical area, with oxygen and BOD5 concentrations of 4.61 mg/L and 51.42 mg/L respectively.

Conclusions:

The station E4 shows the quality of the most contaminated water according to the index applied, since despite the presence of individuals from the Hemiptera and Trichoptera genus that receive a high score in the BMWP/Col index, also, the appearance of groups of macro invertebrates indicators of poor quality waters such as the Diptera of the family Ephydriidae, Culicidae and Chironomidae.