Comprehensive diagnosis of an urban river. Application of biological, physicochemical and riparian forest metrics

Abstract

Urban aquatic environments are highly affected by point or diffuse source pollution. The objective of this work was to determine the anthropic impact on an urban river in the province of San Luis, Argentina, by estimating its physicochemical, biological and hydromorphological quality. The study area focused on a river with anthropogenic impact, where samples of water and benthic macroinvertebrates were taken for two years in periods of low and high water, in five sites (n = 40), a quality index of riverbanks (QBRs) was adapted for the cities of Juana Koslay and San Luis. Physicochemical parameters analyzed were pH, temperature, turbidity, conductivity, total dissolved solids, dissolved oxygen, biochemical oxygen demand, organic matter, and nitrate and phosphorus concentrations. A simplified physical-chemical index of water quality (ISQA) was applied. Samples of macroinvertebrates were taken using a D net, they were identified in the laboratory, and the Biotic Index for the San Luis Sierras (IBSSL) and the Biological Monitoring Working Party (BMWP) index were applied. Taxa richness and abundance were estimated, and the comprehensive ESCOTRIMED index was applied. The ISQA index and the biotic indices showed a gradient from polluted environments to extremely polluted environments. Macroinvertebrate richness and abundance decreased downstream, following an increasing pollution gradient. The integration of the physicochemical, biological and riparian parameters made it possible to determine the impact resulting from the increasing urbanization of the river, showing from environments with strong signs of alteration to areas with incipient deterioration