The eutrophication of an aquatic ecosystem can be slowed or reversed by slowing the addition of nutrients to the system. Sources of excess nutrients can be physically blocked from entering the affected ecosystem. Alternately, these sources can be treated to remove nutrients at a point upstream of the affected ecosystem.
Bodies of water become eutrophic due to an increase in available nutrients, most commonly phosphorus and nitrogen. Some high-nutrient waste streams enter lakes and rivers accidentally; others are deliberately dumped as a means of disposing of unwanted materials. Common sources of nutrients are agricultural manure and fertilizer runoff and municipal waste water effluent.
Farming practices, such as reduced tillage, reduced fertilizer application and cover cropping, help minimize the amount of fertilizer runoff that occurs. Fences and vegetative buffer zones further prevent soil and water-soluble fertilizer from leaving agricultural fields and entering lakes and streams. Agricultural manure sources that are contained, treated and managed properly and that do not flow directly into lakes and rivers further help prevent eutrophication. It is also important that cattle and other livestock be prevented from grazing near or walking across streams and rivers. A private homeowner can reduce the amount of lawn fertilizer that he uses and use lawn-care products low in phosphate.