Large parts of southern Britain are suffering from drought conditions in the wake of an exceptionally hot, dry April, the Centre for Ecology and Hydrology has said.
In its monthly summary for April, the centre said England and Wales received the lowest March and April rainfall since 1938, with a few regions suffering the lowest rain in records dating back more than 100 years.
East Anglia and the East Midlands received just 12% of the average rainfall for the period, and all of England and Wales saw exceptionally low levels of rain.
River flows in a number of rivers by the end of the month including the Exe, Tone, Wye, Tawe and Ribble were similar to, or even below, those seen during the 1976 drought, the summary showed.
It was the hottest April across the UK in records dating back 100 years, and a longer record for central England shows it was provisionally the warmest April in the area for more than 350 years.
The Centre for Ecology and Hydrology (CEH) said the exceptionally dry spring, which follows a relatively dry 2010, had resulted in agricultural and hydrological drought conditions affecting large parts of southern Britain. The amount of water replenishing reservoirs was "very meagre" and reservoirs saw their second largest March/April decline since 1997.
Water companies have been drawing from alternative sources where possible to conserve reservoir stocks, and most reservoirs remain above 80% of capacity, the CEH said, but stocks are well below the late spring average in parts of the South West, Wales and Yorkshire.
Some groundwater aquifers remain within the normal range for the time of year, but others in the south and west of England are well below average levels.
Terry Marsh from CEH said: "Historical rainfall figures indicate a tendency for dry spring periods to be followed by above-average summer rainfall. But with evaporation rates increasing, even average summer rainfall would imply very low late summer river flows - and an associated major contraction in the river network."
Environment Secretary Caroline Spelman told the Commons that she would convene a water meeting next week with water companies, farming and environment groups to make sure the country was prepared for drought conditions.