Monitoring and assessment of surface water quality in Taquari-Antas Watershed, South Brazil—region with intensive pig farming

Pig farming is one of the human activities carried out to meet the increasing food demand by the increasing population. South Brazil is the region with most intensive pig farming in the country, exerting pressure on the water and soil environments by the relevant pollutant emissions. Therefore, the main objective of this work was to assess pig farming pollution by monitoring superficial water qualities of the Taquari-Antas Watershed in South Brazil. The study area is about 8062 km2 (south latitude 292,614, 282,624 and west longitude 520,802, 504,554). In 2014, there were 861 pig farmers and 739,858 animals were slaughtered. Samples were collected bimonthly from 13 spots during 2 years of monitoring. The main analysis included the determination of the water quality index (WQI)—a nine physicochemical and microbiological parameter index—and the trophic state index (TSI), which gives a trophic degree based on phosphorous and chlorophyll-α concentration to assess the impacts of the pig farming on superficial water of the region. The results suggest that the regions with high concentration of finishing stage farms present a higher risk to water quality. A distance of 4 km between different spots was enough to detect a significant decrease in the WQI. The WQI was found ranging from “regular” to “good” (62.77 and 78.95). The TSI were found to be mesotrophic at every spot during the entire period of the study.