Dead Zone

During the late summer, Lake Erie can form a “dead zone.” The dead zone is a large area of low-oxygen water located in Lake Erie’s central basin, approximately 45-55 feet below the surface. No fish can live without oxygen; thus the term dead zone. This water is colder and has a low pH. These conditions can also cause the water to absorb manganese from the bottom of the Lake, which is not harmful to drink but can cause water discoloration.

How does the dead zone form?

Changes in farming practices, especially in western Ohio and eastern Indiana, have caused increasing amounts of phosphorus to enter Lake Erie. The timing and amount of phosphorous that ultimately reach the Lake each year are affected by weather conditions. Heavy spring rains lead to more water runoff. The phosphorus is food for algae living in the top layer of water and leads to huge algal blooms. As algae die, they sink to the bottom of the Lake. The dead algae consume oxygen as they decompose — the larger the blooms of algae, the greater the probability that a dead zone will form. When the oxygen is gone, fish can no longer live there and a dead zone has formed.

How does this affect drinking water?

Under the right weather conditions, dead zone water can shift vertically and horizontally in the Lake and reach one of Cleveland Water’s four intakes. Cleveland Water is vigilant in watching for dead zone water and will adjust its treatment to deal with it. Such water can, at times, be extremely difficult to treat, and the final treated water may be impacted by elevated levels of manganese from the dead zone. If dead zone water does manage to reach the distribution system and customers, there are no health issues associated with it but the water could have an unpleasant color. Cleveland Water works hard to mitigate these conditions and eliminate dead zone water from the distribution system.