Reservoirs are human-made lakes for storing water that will be treated for drinking. A reservoir is a very complex system. Its water is affected by everything that goes on in the surrounding area - known as the "watershed" - such as industries, highways, farms, golf courses, flocks of birds, wildlife and farm animals, recreational fishing and boating, etc. Temperature, rainfall, and water usage also affect the health of a reservoir. A reservoir manager must:

• monitor and control pollution and erosion in the land surrounding the reservoir, including wild animals and birds that can pollute the water;
• monitor and control the conditions that can lead to algae growth (which can then affect the taste and odor of the water);
• oversee the water quality sampling of the reservoir water;
• understand environmental regulations, such as laws requiring that water be released for downstream fish and wildlife habitats (natural places to live);
• maintain a safe environment for the public and employees in and around the reservoir.