Hydrochemistry and nutrients dynamic in the Suquía River urban catchment’s, Córdoba, Argentina

Abstract

Suquia River is a medium-sized hydrological system (basin area of 7,700 km2) that supplies fresh water to Cordoba city, a town of 1,500,000 inhabitants in central Argentina. This paper examines the present-day hydrochemistry of Suquıa River urban catchment analyzing its major and minor dissolved components, and the nutrients variability by means of QUAL-2K modeling software. The Suquıa River has bicarbonate-type waters upstream the city and sulfate-type waters right downstream, whereas they exhibit a mixed-to-alkali-type cationic composition. The seasonal analysis of its major dissolved constituents clearly showed a dilution process during the wet season (i.e. austral summer). In the last 20 years, the Suquıa River has modified its anionic composition, now showing higher relative concentrations of SO42- as a consequence of urban activities. However, trace elements dissolved concentrations do not evidence a strong pollution effect. Nutrients [nitrogen species, total phosphorous (TP)] and related parameters, such as biochemical oxygen demand (BOD), and dissolved oxygen (DO), evidence a clear influence of human activities. The QUAL-2K model was used to evaluate the spatial behavior of selected nutrients and associated variables, (i.e. TP, N-NH4+, N-NO3-, DO, BOD). Nutrient concentrations are affected by point sources of contaminants, particularly domestic waste and sewage, as well as by diffuse agricultural pollution. A calibrated QUAL-2K modeling exercise clearly shows the impact of the Cordoba city´s municipal wastewater treatment plant on the Suquıa River water quality.