Eutrophication is an ecological process, akin to aging, in which a water body is increasingly enriched with organic matter. Although the most obvious signs of eutrophication in lakes and rivers involve algal blooms and fish kills, the systemic of eutrophication, although profound, are often not as noticeable to the casual observer. Eutrophication of lakes and rivers is accelerated by nutrient pollution, one of the most pervasive water quality problems in the world. Increases in populations and intensification of land use have accelerated eutrophication of water bodies from the Great Lakes of North America, to Lake Tai of China to Lake Victoria in Africa. Because nutrients can come from many sources, point as well as nonpoint, comprehensive strategies are required to curb eutrophication. A variety of watershed programs have yielded success, but they are outnumbered by the ever‐expanding number of lakes and rivers that are undergoing eutrophication.

Key Concepts:

• Eutrophication of lakes and rivers is caused primarily by inputs of phosphorus and nitrogen.
  
• Accelerated eutrophication can render a water body unusable for many uses, from fishing to swimming to drinking water.
  
• Point source pollution comes predominately from industrial sources and wastewater treatment plants.
  
• Nonpoint source pollution, or diffuse pollution, derives from urban and rural land uses, ranging from lawns and golf courses to agricultural fields.
  
• Watershed management is required to successfully control eutrophication, involving comprehensive programs that tackle the many sources of nutrients in a watershed.
  
• Nonpoint sources of nutrients, such as soils, sediments and groundwater, are extremely difficult to combat, requiring decades to reverse.