Bentonic Invertebrates Indexes Used for Determination Environmental Quality Rio Gallegos's Upper Basin. Santa Cruz. Argentina

The Rio Gallegos upper basin is integrated by several water courses: San Jose and Turbio creeks and Rubens and Penitente rivers confluences conform the Gallegos. river. Differents anthropic activities are developed in the basin: coal mining, since 1936, is the main historical economic activity. 28 de Noviembre and Rio Turbio town's (population near 10.000 inhabitans) are narrow related with this activity. The urban sewage compound by either domestic or industrial effluents are directly dumped into the water courses without treatment at all. The response of benthic macroinvertebrate communities to human activities was studied extensively in different geographical regions. Meanwhile they had not been neither studied nor used on the water resource in the study area depict the high environmental impact of the activities that take place there. Different physicochemical analyzes were carried out. The benthic macroinvertebrates community was characterized and different biotic indexes were applied to determine the watercourses environmental's state of this basin's sector. An raise rate in conductivity, iron and QOD values, among others, was detected at the site closest to the industrial activity. This alteration made modifications in the benthic macroinvertebrate community, which presented significant differences between the sites sampled. Diverses biotic indices were used, being the Biotic Monitoring Patagonian Streams (BMPS) the one of them that showed the greatest sensitivity for the determination of the environmental quality of the water resource. The results shown that the watercourses's quality varies between: heavily contaminated in the vicinity of industrial activity, and incipient contamination in places furthest away from these activities mainly beyond the river. confluence mentioned. The main environmental impact is caused by urban sewage and mining activity.