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United Nations Environment Programme
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Newsletter and Technical Publications

Lakes and Reservoirs vol. 3

Water Quality: The Impact of Eutrophication


We are pleased to introduce Volume 3 of the Short Series on the “Planning and Management of Lakes and Reservoirs”. The present Volume entitled “Water Quality: The Impact of Eutrophication” provides an overview of the problem of the enrichment of surface freshwater bodies due to organic compounds originating from urban and agricultural activities as well as from industrial effluents. Eutrophication is a process that once started is difficult to control unless immediate action is taken. Eutrophication ultimately leads to the reduction of oxygen in water, the release and accumulation of toxic substances in the water and sediments-polluting the aquatic environment, which can lead to the death of aquatic organisms, ecosystems and humans that may inadvertently drink or be exposed to the polluted water. If eutrophication has already started it is very difficult and costly to control or revert. Around the world there are some eutrophied lakes, but the majority of the world’s lakes are not. This situation is changing rapidly.

Waters in eutrophic lakes and reservoirs bring enormous losses of biodiversity, reduced water quality and availability. Furthermore, such lakes and reservoirs represent a significant health hazard for humans and animals alike. This is primarily due to the explosive growth of microscopic algae which once dead and in the process of decay release one of the most powerful classes of toxins known to man: Cyanotoxins. Damage to electric power plants and recreational activities are also well recorded as negative impacts originated from these process cause large economic losses.

To control the process of eutrophication there is a need to understand the causes and the stages of development. Similarly, it is necessary to carefully assess and evaluate the technological solutions to be applied in the mitigation and remediation of the eutrophication process. In general conventional wastewater treatment systems are sufficient for the purpose although they tend to be very expensive to maintain. Alternative methods of eutrophication control and mitigation include the use of natural wetlands as well as constructed ones since they are based on the capacity of self purification of nature and are usually much cheaper to maintain and operate.

Eutrophication in many ways can be considered as a reflection in our lakes, reservoirs and rivers of the careless way in which society is dealing with its liquid wastes as well as the application of unsound land use practices. Therefore, the society as a whole needs to be aware of the problem in terms of health, finance, environment and recreation as well as the costs related to its solution. It is expected that through this publication citizens together with the authorities, industries, farmers and other members of the society can grasp the principles of this process, the effects and remediation so that proactive, co-operative action can be taken to prevent or significantly reduce the risk of surface water bodies becoming polluted through the process of eutrophication.

We hope you enjoy it.

Steve Halls
Director
International Environmental Technology Centre
Kei Yamazaki
Director General
International Lake Environment Committee Foundation
   

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  • International Year of Forests
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