A monitoring program enabled the evaluation of water quality and the simulation of the pollution dynamics of the rivers in the Joya de los Sachas and Francisco de Orellana cantons in Ecuador. One used the WQI (water quality index) and the pollution indices ICOMO (organics contamination), ICOSUS (suspended solids), ICOMI (mineralization), ICOTRO (trophy system), and ICOpH (pH Index). The mathematical model operates with several input parameters, including dissolved oxygen, fecal coliforms, the biochemical oxygen demand (BOD₅), turbidity, total solids, total phosphorus, pH, total nitrogen, suspended solids, alkalinity, conductivity, temperature, and the concentrations of nitrates, nitrites, and phosphates. WQI values were obtained from ICO pollution indices. The pollution of the Sacha area is significant, WQI = 0.292, which represents an advanced degree of pollution since increased BOD values correspond to a high load of organic pollutants. They can originate from household, agricultural, industrial, and soil erosion waste. Likewise, the Sacha River has an ICOSUS = 0.16, which renders water treatment difficult, without impacting human health. Calculated WQI values reveal that the water quality of the Sacha, Basura and Coca rivers is low, being highly contaminated. In contrast, the Huamayacu, Jivino Rojo, Jivino Negro, and Jivino Blanco rivers are commonly polluted.

Study Area

The study area of this project included the experimental farms of the examined components in the Parishes San Carlos, San Sebastián del Coca, Tres de Noviembre, San José de Guayusa, the Joya de los Sachas and Francisco. Investigated were the experimental farms of Orellana components, in the Province of Orellana, which correspond to an area of 1205.6 km². Four reference points have been selected for sampling on the Sacha River and on the Basura River experimental estates.

Methodology

To assess the water quality and simulate the pollution dynamics of the rivers in the Joya de los Sachas canton for agricultural use, preservation of aquatic life, and recreation, one sampled and characterized river water at the monitoring points. Subsequently, one performed calculations and analysis of quality indices WQI, ICOMO, ICOSUS, ICOpH, ICOTRO, and ICOMI.

Sampling and characterization of monitoring points

 The sampling points were selected by considering the use of oil, anthropogenic activities close to the rivers, the accessibility, width, and depth of the rivers. By this approach the authors designated 5 monitoring points at the Sacha River, 5 at the Basura River, 6 points at the experimental farms assigned to zootechnics, and 5 points at the sector assigned to agronomy. At each monitoring point one carried out an integrated sampling, according to the following criteria: for rivers over 10 m wide 1 sampling point was chosen for every 2 m of the river width (Morales-Guzmán et al. 2022; Castle 2015), and a total of 21 points were monitored. To obtain a better representativeness of the water bodies’ quality, the samples were collected monthly, from October 2019 to February 2020, to coincide with the rainy and dry seasons (Alvarez et al. 2019). In each of the 21 points one determined: dissolved oxygen (DO), turbidity, dissolved total solids, pH, alkalinity, conductivity, temperature, and the concentration of three ions: ammonium (NH₄⁺), nitrates (NO₃^-), and nitrites (NO₂^-).