Evaluación de la calidad del agua del río Tomebamba basado en un análisis jerárquico para identificar los pesos de los parámetros de un índice propio de calidad del agua

Abstract

In this research, the water quality of the Tomebamba River was evaluated by applying four indexes already established in other parts of the world and by creating our own index based on an analytical hierarchy process for assigning weights to the parameters used in this index. The study area corresponds to the Tomebamba River, starting from its source in the sector known as tres cruces in the Cajas National Park to its intersection with the Cuenca River. The water quality data recorded by ETAPA EP at the different monitoring points located in the river sub-basin were used for this study. The information from the data of the monitoring stations was analyzed, determining 10 stations for the analysis, this in view that they cover the entire trajectory of the river, the water quality was analyzed in a period of 8 years from 2012 to 2019, for which 4 water quality indexes were applied the NSF, Dinius, Oregon and the CCME index. The creation of the index itself started from the identification of the most important parameters through a correlation analysis, subsequently the analytical hierarchy process (AHP) was applied for the identification of the weights of the selected parameters. According to the results of the river water quality, both the NSF, Dinius and Oregon index presented identical results of water quality; in the stations of the upper part the water quality is much better than in the lower parts, however, the NSF and Oregon index classified the water quality in a general way, while the Dinius index categorized the water quality according to the general criterion and the criterion of human consumption. On the other hand, the CCME index determined the water quality for each monitoring station by categorizing it as good in the high part, regular in the medium part, and poor in the low part. With the AHP, the weights of the most important parameters were quantified statistically, with fecal coliforms being the parameter to which the respondents assigned the greatest weight, followed by color and BOD5; according to the index itself, the water quality results were very similar to the results of the aforementioned indexes. To corroborate the results of the own index, a correlation analysis was applied with the results of the NSF and the Dinius index, showing very good correlation results above 0.5 in most of the selected stations, reaching the conclusion that water quality decreases as the concentration of water quality parameters increases. Applying multiple linear regression, the equation that best fits the data for calculating the AQI on other dates and stations of the Tomebamba River was determined. These results will be useful for ETAPA EP to plan, manage and carry out activities for the benefit of the water resource; likewise, the index itself can be applied to other rivers in Cuenca