The scientists studied the water quality in the Songhua River Basin from 2006 to 2009 and found positive changes. They looked at different areas and pollution levels. The water quality got better over time, with more clean water and less polluted water. During floods, water quality was slightly worse than usual, but better in non-flood times. Pollution hotspots shifted from smaller cities to bigger cities along the main river. New indicators like ammonia nitrogen showed water pollution. Overall, the Songhua River Basin's water quality improved from 2006 to 2009.