Runoff has created a huge debacle in Ohio:
http://thinkprogress.org/climate/2014/08/03/3467068/toledo-ohio-water-crisis/
Algae blooms happen, but humans contribute to the extreme severity of this one. According to the article:
“Experts say one of the biggest reasons for the severity of this algal bloom is excess phosphorus runoff from urban and industrial agricultural lands, as well as from waste water from sewage treatment plants. NOAA notes that this increased runoff into the lake is largely due to poor farming practices, such as high use of fertilizers and presence of livestock near water supplies. Pesticides also impact the blooms, NOAA says.”
I wish the new media would talk about the potential contribution of lawn fertilizer. Farmers have, over time, learned how to target the least amount of fertilizer to their lands to minimize cost and run-off. The average lawn owner possesses no such expertise.
The Lawn League 