Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito

The study of water quality is important over time because it is an essential element for human beings, it has been vital for their survival, territorial expansion, and socioeconomic development. The water of the Monjas river present contamination issues, mainly due to human activities such as agriculture, animal husbandry, and gray water discharges that alter their chemical, biological, and physical properties. The purpose of this research is to evaluate whether the water conditions are suitable for agricultural use, applying the Water Quality Index (WQI) methodology, which requires a study in the laboratory for fecal coliforms, dissolved oxygen, pH, biological demand for oxygen, nitrates, phosphates, dissolved solids, turbidity, and temperature. Samples were taken at six sampling points along the riverbed. Results were compared with the parameters described by TULSMA (Texto Unificado de la Legislación Secundaria de Ministerio de Ambiente), and FAO (The Food and Agriculture Organization of the United Nations) environmental regulations. Higher values were obtained for fecal coliforms, and biochemical oxygen demand that exceeded the maximum permissible limits with respect to the rest of the parameters examined. In this study, the WQI ranged from 26 to 50, classifying the water quality of the Monjas river as unsuitable. It implies that it is not appropriate for agricultural use due to the contamination that it could cause to the crops. The main reasons for this could rely on the presence of fecal matter of human, and animal origin, fertilizers, pesticides, and household waste.