DATA ANALYSIS AND SPATIAL MAPPING OF DISSOLVED OXYGEN IN THE ANDROSCOGGIN RIVER FROM 1930-2019
Average August DO data from 1930-2019 was considered spatially and temporally to evaluate remedial actions by the paper companies and government. August data were used in this study because it is the most consistently sampled month, and because DO concentrations and discharge are at their lowest. The shift from sulfite to Kraft pulping between 1959-1965 led to the first notable increase in DO since annual monitoring began in 1948. The CWA resulted in the most significant improvements in water quality, bringing the average DO above 5 ppm at almost every site following 1977 and making nearly every stretch of the river habitable by fish year-round for the first time in at least 35 years. Results also indicate reduced variation in average DO between June-September post-CWA, compared to pre-CWA data. Surveys focused on the Gulf Island Pond, a 14-mile-long impoundment north of Lewiston, document slight improvement in surface water DO levels after 1992. The reduction of organic-rich municipal and industrial waste discharges has greatly improved DO in the Androscoggin River, however it remains the dirtiest of Maine’s major rivers despite decades of remedial efforts.