An anonymous reader shares a report from National Geographic: If climate change continues to progress, increased precipitation could mean detrimental outcomes for water quality in the United States, a major new study warns. An intensifying water cycle can substantially overload waterways with excess nitrogen runoff -- which could near 20 percent by 2100 -- and increase the likelihood of events that severely impair water quality, according to a new study published by Science. When rainfall washes nitrogen and phosphorus from human activities like agriculture and fossil fuel combustion into rivers and lakes, those waterways are overloaded with nutrients, and a phenomenon called "eutrophication" occurs. This can be dangerous for both people and animals. Toxic algal blooms can develop, as well as harmful low-oxygen dead zones known as hypoxia, which can cause negative impacts on human health, aquatic ecosystems, and the economy. In the new study, researchers predict how climate change might increase eutrophication and threats to water resources by using projections from 21 different climate models, each of which was run for three climate scenarios and two different time periods (near future, 2031-2060, and far-future, 2071-2100).