With high pressure dominating for most of the month, October was notably dry for most of the UK. Although there were warm spells, easterly winds brought temperatures close to the seasonal average. There was a good deal of autumn sunshine, although there were regional variations: it was exceptionally sunny in north-west Scotland, while sunshine was near-average in the east. The dry October extends appreciable rainfall deficiencies which have developed since July in southern England. With significant soil moisture deficits (SMDs) persisting in many areas, river flows and groundwater levels generally continued to recede. October river flows were below normal across much of the country, and exceptionally low in some western index catchments. Groundwater levels generally remained in the normal range or moderately below. With depressed autumn runoff, reservoir stocks declined – steeply in many impoundments – but at the national scale stocks are generally near-average (although 7% below average for Northern Ireland). Stocks were substantially below‑average in some areas, particularly in some impoundments in south-west England where stocks have declined steeply since the spring; for example, Clatworthy registered 34% below average, its third lowest October stocks (after the drought years of 2003 and 1989). Overall, the water resources situation is favourable at the national scale. However, the delay in commencement of substantial aquifer recharge or reservoir replenishment suggests continuing vigilance will be required through the winter half-year, particularly in areas where current levels or stocks imply recovery will begin from a below-normal baseline. Current seasonal outlooks slightly favour drier rather than wetter conditions for the winter, albeit with a substantial range of possible outcomes.
The full Hydrological Summary can be found here.