Water Pollution in River Lea

Post date: Sep 28, 2011 6:35:41 AM

Dear all.

The water quality testing teams were out today, taking samples from 9 sites from Tottenham Lock to Bow Locks.

We test for dissolved oxygen on site, with the water samples sent to University College London for further analysis (bacteria, nitrate and phosphate).

The heavy, intense rainfall yesterday coupled with the warm temperatures today have hit the river hard (as it does after every such occurrence).

When the pollution gets washed into the rivers along the Lee Valley it causes bacteria to multiply – this uses up oxygen that fish need to survive. The warmer the water is the less oxygen it can hold.

A healthy body of water should have more than 5 milligrammes of dissolved oxygen per litre of water. Many of the sites today had less than this meaning that fish will struggle (they rarely get above 5).

The worst site had less than 3 mg of dissolved oxygen per litre, meaning it was too low for most fish to live there. Fish in these areas will either die or are more prone to diseases. Where they can they will try to swim to water with more oxygen…It’s not clear whether we’ll see fish dying as in many places there are very few fish (why would they choose to live there when there is so little oxygen in the water).

We’ll get the rest of the results back this week, I’ll let you know what they tell us.

We’ll soon be putting the results online so people can examine them for themselves.

Kind regards,


Theo Thomas

Love the Lee – Save the River