Sunday, December 7, 2014

Lake Oswego: Eutrophication

Eutorphication of Lake Oswego

Author: Geoffrey J. Janke


Eutrophication is a natural process in which nutrients such as nitrogen and phosphorus build up in lakes or ponds over time. Water runoff intro rivers that contain nitrogen and phosphorus is the greatest contributor to eutrophication. Eutrophication affects nearly every body of standing water that is downstream of some form of human intervention. These interventions include fertilizing for agriculture, and landscaping. The eutrophication of Lake Oswego is believed to be a combination of both.

Lake Oswego is owned by the Lake Oswego Company (LOC) that manages the lake and the rights to its use. Lake Oswego is surrounded by homes and the area is populated such that it is hard to view the lake from the streets of the town. It is believed that fertilizers that run into the Tualatin River (a feeder into Lake Oswego), and water runoff from the homes surrounding Lake Oswego contribute to algae blooms.

Though algae blooms have not reached toxic levels LOC has implemented practices to minimize algae blooms. Aerators have been installed in shallow arms of the lake. Residence are not allowed to use nitrous and phosphorus containing fertilizers, and instead are asked to use “lake friendly” fertilizer alternatives. The lake has been treated topically with herbicides and alum to fight the algae blooms.

It is this writer's opinion that fighting the algae blooms of Lake Oswego seem to contribute to the problem. The environment maintains a balance and adding agents to fight the algae blooms may cause for a stronger push back from the environment to bloom again; creating a yo-yo effect. Lake Oswego my be algae free one year and nearly toxic the next.

Fertilizers used to support agriculture and its monoculture of food contribute to eutrophication of water sources like Lake Oswego. Eutropication is yet another argument against large agribusiness and in favor of more biodiverse multi-sourced farming.



Pearson Education, Inc. (n.d). Algal Blooms, Key Concepts. Retrieved from:

Muir, P. (2012). Eutrophication. Retrieved from:

Oregon Department of Environmental Quality. (2011). Oregon DEQ Harmful Algae Bloom (HAB) Strategy, Appendix C. Retrieved from:

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