• 
• Japanese
• 
• IETC's Focal Area
• Waste Management
• Publications & Tools
• Meetings & Workshops
• Global Partnership on Waste Management
• Background
• Objectives
  & Expected Outcomes
• Framework
• Sub-focal Areas
• Information Platform
• Meetings
• Participation / Membership
• Water and Sanitation
• Publications & Tools
• Meetings & Workshops
• Resources
• Publications & Tools
• About IETC
• Background and History
• Director
• Activity Reports
• Supporting Foundations
• Internship
• Contact Us

Executive Summary

Introduction

Fresh water available to humans, animals, and plants is not evenly distributed on the earth's surface. Sharp differences exist in the amount of total annual precipitation in different parts of the world. The amount of precipitation also varies from one season to another during the year. In areas with low precipitation and in urban and industrial areas, there will be increasing competition among water uses, which will require a change in water resources management. Lakes, water reservoirs, and streams, which are the most valuable sources of drinking water for the earth's population, are vulnerable to pollution and degradation of water quality, particularly to eutrophication. Accelerated eutrophication of lakes and reservoirs during this century is a serious degradation of water quality in most parts of the world. Prevention of eutrophication or restoration of eutrophic lakes and reservoirs require proper planning and management of the associated watershed.

This publication deals with the problem of eutrophication of lakes and reservoirs by looking at its origin, consequences, solutions, and prognosis by an integrated approach. Comprehensive information on the most important issues, which need to be considered in the planning and management of prevention and/or remediation of eutrophication of lakes and reservoirs, is provided in seven chapters of this publication. Environmental, social, and cultural aspects of eutrophication, policy, institutional and regulatory framework, public awareness and education, and economic, technical and managerial aspects of eutrophication, are discussed in detail in the chapters. The information provided in the seven chapters is synthesized in Chapter 8. Numerous examples from different countries and ecosystems are included to help the reader to better understand the content of each chapter. The publication outlines a new approach to water resources management, particularly eutrophication, emphasizing the need to simultaneously solve social, cultural, economic, and other associated problems considering, at the same time, the natural setting of the lake or reservoir and its environment. The watershed approach to management is highlighted in this publication. The following is a summary of the content of the eight chapters.

Chapter 1

Enrichment of lakes and reservoirs with plant nutrients, particularly phosphorus and nitrogen, leads to eutrophication accompanied by degradation of water quality. Augmented nutrient input to inland waters usually result from the modification of the watershed, such as deforestation, agricultural and industrial development, and urbanization. Environmental conditions within the water bodies and in the watershed and airshed all influence eutrophication. Climatic and hydrological conditions in the watershed further alter impacts of eutrophication. Symptoms of eutrophication include algal scum and toxins derived from algal blooms, massive infestation of certain aquatic plants, increased incidence of water-related diseases, turbid water, noxious odours and poor tasting water, depletion of dissolved oxygen in the water, and tainted fish and fish kills. However, positive impacts of eutrophication, such as enhanced plant production and improved fish yields, do occur and can be important, particularly in countries where fish and other aquatic organisms are a significant source of food. Examples of positive impacts are described.

Most strategies for the management of eutrophication have been developed in temperate climates for highly developed economies and may require modification for application to other regions and economic conditions. Assessment of conditions in a particular lake or reservoir should be performed before a management strategy is employed. An understanding of the functioning of a lake or reservoir obtained from long-term descriptive data, experimental manipulations, and integrative models are useful in the evaluation of management options. The scientific basis for evaluating the causes and impact of eutrophication is encompassed by limnology. Limnology has a long and successful tradition of applying scientific knowledge to the management of inland waters. Consequently, it is suggested that training in limnology should be an integral part of the education of anyone responsible for the management of lakes and reservoirs. A brief review of limnological concepts relevant to the eutrophication of lakes and reservoirs is provided. Characterization of eutrophication and a summary of its effects follow the review. Examples are presented to illustrate the nature of these effects. They include tropical South American and Ukrainian reservoirs, subtropical Lake Okeechobee in the U.S.A., Laguna de Bay in the Philippines, the North American Great Lakes, and prairie lakes in Canada and the U.S.A.

Environmental conditions within lakes and reservoirs and in their watershed all influence eutrophication. Rivers and streams are major routes of the transfer of nitrogen and phosphorus, and they integrate point and non-point sources of nutrients. Recycling of nutrients from sediments to overlying waters can sustain eutrophic conditions for long periods after the external loading is reduced. The primary step in the reduction of eutrophication of a lake or reservoir is to limit, divert, or treat inputs of nutrients and associated particles. However, because lakes and reservoirs can trap and recycle nutrients and organic matter, reduction in loading from the watershed may not reverse the impact of eutrophication. Therefore it may be necessary to modify internal chemical, biological and physical processes. Modeling approaches for assessing the processes are briefly outlined. It is suggested that the prediction of changes of physical, chemical, and biological processes should be based on available information on the lake and reservoir and on the questions to be answered. Evaluation of eutrophication, particularly in developing countries, must balance benefits gained from increased fertility of lakes or reservoirs against problems associated with the degraded quality of water used for domestic and industrial purposes.

(continued)

Table of Contents

• Brochure
• 
• 



• International Year of Forests
• 
• 



• World Environment Day
• 
• 



• UNEP Campaign
• 
•