|This is the oxygen bubbler that was used to stop fish dying during the Olympic Games. In the summer rivers hold less dissolved oxygen, compared to the winter when of course the water is colder. After heavy rain large amounts of raw sewage flow down the Lea from Deephams Sewage Treatment Works in Edmonton. Add to this the run-off from the roads and oxygen levels crash as the bacteria in the pollution use it up. Fish, if they can't escape, die. So the bubbler kept the oxygen levels up on the section of the City Mill River which passes the Olympic Stadium on the eastern side and is the first waterway you met if you walked from West Ham.