Spatio-temporal variability of river water quality of COVID-19: A case study of Opak and Progo Watersheds (Indonesia)

The imposition of community activities due to the COVID-19 outbreak positively impacted the environmental quality in various countries, including improving river water quality. This paper examines the spatio-temporal variation of water quality of the Opak and Progo Watersheds after the second wave of COVID-19. This study utilized primary and secondary data obtained from observation, literature study, and data documented by several agencies. Data were analyzed statistically employing an independent sample t-test and simple linear regression, matching, pollution index calculation, and Geographic Information System (GIS) analysis using Average Nearest Neighbor (ANN). The results show that restrictions on community activities that have been repeatedly implemented during the pandemic have improved water quality. However, quality improvement is only found in a few parameters. Heavy metals from transportation, Pb and Cd, tend to be low and decline during pandemics. Pb decreased from 0.2 ppm in 2020 to 0.1 ppm in 2021, while Cd decreased from 0.0033 ppm in 2020 to 0.0008 ppm in 2021. TDS and TSS were smaller during the pandemic due to reduced erosion of farmland. The downward trend in TDS and TSS also impacted the decline in BOD. After the pandemic, most water quality parameters met the national quality standards. Good water quality parameters are dispersed in the study area. This condition indicates the spatial homogeneity of water quality in both watersheds, without pollution zones, even in the megacity of Yogyakarta. In summary, this study presents new insights into understanding the impact of the COVID-19 pandemic on river water quality in watersheds characterized by the dominance of population activities in rural areas.