December was a remarkably dry month for most of the UK, with mild temperatures bookended by two cold and frosty periods. The majority of the UK received below average rainfall, with much of England and Wales receiving less than half of the long-term average. It was particularly dry in southern England, further extending the rainfall deficiencies which have developed here since early summer. December river flows were below normal across much of the UK, and exceptionally low in most catchments in southern England. Groundwater level recessions continued in many index boreholes and were generally in the normal range or below, with notably low levels in parts of southern England. Reservoir stocks fell relative to average in many impoundments and were substantially below average in some regions, particularly in southern England where stocks have declined steeply since the summer. Stocks at Ardingly were 40% below average, the third lowest December stocks (after 2011 and 2003) in a series from 1987. A continuation of the below average rainfall received since the early summer and a further delay in aquifer recharge could have a significant impact on the water resources outlook in 2017. Particular vigilance is required in those parts of the UK with seasonally depressed groundwater levels and below average reservoir stocks, where any recovery will start from a below-normal baseline.
Read the full Hydrological Summary here.