The first Hydrological Summary was published 30 years ago and described the hydrological conditions of December 1988. The 30th Anniversary Edition of the Hydrological Summary for the UK is now available.
December was a mixed month, with mild changeable conditions interspersed with more wintry weather. Despite the above average temperatures across the UK for December as a whole, wintry snaps brought colder temperatures, freezing rain and some snow to the north and west. Rainfall was near average at the national scale, but this masked a marked north-south contrast. Above average rainfall was received across much of England and Wales, but some regions in the north registered substantially lower than average rainfall. December river flows were generally in the normal range, but were below normal in northern Scotland and above normal in the south-west of the UK. Soil moisture deficits (SMDs) were negligible across most of the country, but almost all groundwater levels remained in the normal range or below. The groundwater recharge season started after delayed onset, with the exception of boreholes in the Chilterns and eastern Chalk. Reservoir stocks for England and Wales were near average, although some impoundments in the north remained below average despite stocks increasing by more than a fifth relative to average (e.g. Derwent Valley and Washburn). Although a wetter December has been beneficial for the water resources situation in southern Britain, the effect of long-term rainfall deficits remains apparent. With below average reservoir stocks and groundwater levels in some areas, above average rainfall is still needed in late winter-early spring to reduce the likelihood of water resources stress in 2019. With near-zero rainfall across much of the UK in January so far and current forecasts indicating drier than average conditions over the next three months, continuing vigilance is required.
The full Hydrological Summary can be found here.