The researchers monitored total nitrogen levels in Danjiangkou Reservoir and found that they have been stable in recent years, but were higher than allowed in 2008. Nitrogen levels were highest during wet periods and at the end of the reservoir, and lowest during dry periods and at the largest bay. Pollution from rivers, soil erosion, agriculture, and industry are likely sources of nitrogen. To protect the reservoir, pollution control measures should be increased, including monitoring sediment levels.