Biological Evaluation of Water Quality with the BMWP Index in a Section of the Tlapaneco River Affected by Two Rural Communities in the Guerrero Mountains, Mexico

Anthropic activities as agriculture and livestock and wastewater discharges affect water quality in the Tlapaneco river in the Montaña region of the state of Guerrero, México, which is a tributary of the great Balsas River that flows from the Montaña and discharges into the Pacific Ocean; the water resource in the localities mentioned is used for agricultural work, recreation, and domestic tasks. The objective of the work was to evaluate quality of the water in the stretch of influence of two localities, Patlicha and Copanatoyac. The instrument used was the BMWP biotic index and some physicochemical parameters. Nine sampling sites were selected according to the perception of the local community with respect to disturbance; the study area was divided into three: high, medium and low. Twenty-seven collections of macroinvertebrates and water were analyzed, in dry and rainy seasons, through the presence-absence of these organisms and physicochemical analysis to evaluate water quality. The results showed that the conditions of the riverbed associated with daily activities and domestic discharges are important factors in the composition of the families. Water quality was very poor to fair according to the macroinvertebrate assemblages collected. The BMWP index with fair quality was when the families Leptohyphidae, Chironomidae, Hydropsychidae, Leptophlebiidae, Baetidae, Simuliidae, Veliidae, Corixidae, Hydrophylidae, Lestidae and Ephemerellidae were present; in sites with poor quality, the families Chironomidae, Leptophlebiidae, Veliidae, Corixidae, Hydropsychidae, Leptohyphidae, Hydrophilidae, Baetidae and Simuliidae were found, while in very poor quality the family present was Corixidae.