The lakes of death bred by rain and sun

Millions of gallons of black and stinking floodwater have caused a farming and ecological disaster on one of Britain's most important and unusual wetlands.

Thousands of fish - bream, pike, roach and others - have been killed by the stagnant, deoxygenated water which has covered hundreds of acres of the Somerset Levels for the past month. Rich cattle pastures have been wiped out.

The Government's Environment Agency is using large quantities of hydrogen peroxide, a volatile, corrosive chemical, to raise oxygen levels in the floodwater, so that it can be pumped off the fields and into a river without killing more fish.

Exactly a month ago, heavy downpours flooded more than one thousand acres of land. When the rain stopped and the sun shone, the temperature climbed and bacteria began to rot the lush grass and cattle dung lying below the surface.

The microbes consumed most of the oxygen dissolved in the water within a few days. The decomposition turned the water black, produced a foul stench and killed the abundant fish, snails and water insects living in the network of ditches and dikes which drain the levels.

First the Environment Agency tried pumping the water into nearby rivers, which just killed more fish. Then they bubbled fresh oxygen through the water, which was simply too large a task - there are 50 million gallons of water after all.

Their last hope was hydrogen peroxide. This corrosive chemical, more normally used as hair bleach, adds free oxygen to water. More than sixty tons of the chemical will have been mixed in by the time the task is finished, probably this weekend. Pumping the then fish-friendly water can then begin in earnest.

The levels around Glastonbury and Bridgwater are mostly Government- designated Sites of Special Scientific Interest. These flat pastures are a haven for more than 10,000 ducks and wading birds in winter and spring. There is a rich variety of plants and smaller animals living on the pastures and in the ditches, although parts of the levels are used for intensive cattle farming.

The National Farmers Union said some 50 farmers were affected. ``The more productive grazing and silage fields will have to be ploughed up,'' said regional director Anthony Gibson. ``The floodwater was like a rancid soup, stinking to high heaven.''

The water which has already receded has left behind brown, dead, vegetation. ``The moor looks very sick, sad and sorry,'' said John Leece, for the Royal Society for the Protection of Birds. Herons have been flocking in to eat all the dead fish. ``There are worries about the vegetation and the fish, but I think the birds are going to be fine,'' said Mr Leece.