Drought spreads across England as soil moisture in Anglia reaches record low
Some 30 sea trout and six salmon have been reported dead.
British Waterways has lowered the water level on the Grand Union Canal at Tring Summit, closing it to through passage.
The drought conditions, which come after two dry winters in a row, have raised the prospect of hosepipe bans in the coming weeks.
Households across all the affected areas are being asked to save water by taking shorter showers and not washing cars or watering lawns with a hosepipe.
Helen Vale, national drought co-ordinator, for the Environment Agency, said saving water now could help ease restrictions later in the summer.
"With the south east of England moving formally to drought this week and many parts of England at high risk, it's more important than ever that we all use water wisely," she said.
"The Environment Agency must balance the water needs of people, businesses and the environment.
"We are working with businesses, farmers and water companies to plan ahead to meet the challenges of a continued drought."

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