Physicochemical and Biological Structure as Indicators of the Environmental Quality of Surface Water Streams

The lower basin of the Cusiana River is an area affected by various socioeconomic activities. This study aims to establish the physicochemical and biological structure of areas influenced by agriculture, livestock, and wastewater discharges from urban areas. Sampling was conducted at two locations, the municipality of Aguazul and the municipality of Maní in the Casanare department, Colombia. Four monitoring surveys were carried out considering seasonal differences in rainfall and drought. The variables analyzed were: temperature, alkalinity, conductivity, turbidity, BOD, COD, total hardness, total phosphorus, nitrates, dissolved oxygen, pH, suspended solids and sampling of benthic macroinvertebrate communities. To assess water quality in the sampled periods, physicochemical indicators ICA NSF were estimated, considering the intended uses of the water resource, and reporting average quality. A total of 1491 individuals were reported, distributed across seven orders and 20 families. The BMWP/ Col index was calculated for the two monitoring stations. The Aguazul station showed doubtful water, categorized as slightly polluted waters, which decreased significantly to moderately polluted waters. The Maní Station transitioned from dubious to critical condition and from moderately polluted to very polluted waters. Studies of this nature allow entities to make informed decisions regarding the proper using and management of the region’s water systems.