Evaluación de la calidad del agua de los ríos de la ciudad de Cuenca, Ecuador

The water quality of the Tarqui, Yanuncay, Machángara and Tomebamba rivers, tributaries of the Paute river was evaluated. Due to the need to incorporate new approaches in the water quality monitoring, this study applied the widely known water quality index (WQI) but, instead of using the 9 parameters originally required by the method, we used 18 physicochemical and microbiological parameters. For each river, nine monitoring campaigns were carried out, covering representative hydrological periods and measuring flow discharges. The results show that, in general, in the areas of river catchment, the water resource is suitable for almost all types of use, but gradually, as it progresses downstream, the quality decreases due to sanitary or industrial wastewater and to natural factors such as runoff or erosion sediments. The most critical condition of the evaluated river’s water quality was presented during drought conditions, mainly due to the decrease in dissolved oxygen and the increase in temperature, salinity, organic matter and coliform bacteria. On the other hand, during rainy periods, parameters indicating a decrease of water quality were color, turbidity, and nutrient content such as phosphorus and nitrogen. In general, rivers have better quality for medium flow conditions, which prevail during most of the year. The present results were analyzed in accordance with the quality objectives established in previous studies, allowing a qualitative evaluation of the wastewater interception and treatment system of the city of Cuenca, Ecuador.