Back to people & env.People & Environment - Water quality
The quality of water can deteriorate when it is stored in a reservoir.
River water contains dissolved oxygen. Sufficient dissolved oxygen is needed to maintain aquatic animal and plant life, and to prevent some types of chemical reactions that form unwanted pollution in the water.
There are many factors that can reduce oxygen levels in a reservoir, for example, organic material in the water can use up oxygen as it decomposes (or rots). The depth of the water, its temperature and its flow can also affect the oxygen levels.
The type of land that is inundated by a reservoir may affect the water quality. Pesticides from farmland and toxic materials from industrial land can pollute the water. Also, the streams and rivers flowing into the reservoir may be carrying pollutants.
The designers of a reservoir have to consider whether any of these factors will have a significant effect on the quality of the water and whether they have to include special measures to offset any problems that could occur.