For both river flows and groundwater levels, the outlook is for a normal to below normal signal across south-eastern England over the next one to three months. River flows in northern and western parts of the UK are less certain, although flows within the normal range are most likely for February.
The typical rainfall gradient across the UK was reversed in January, with dry conditions over the north and west, and slightly wetter than average conditions in the south-east. The driest areas of the UK saw precipitation less than 30% of the January average, whilst larger areas of northern England, Scotland and Northern Ireland received less than 50% of average. Rainfall over the past 6 months has been 50-90% of average for the majority of the UK.
The rainfall outlook for February (issued by the Met Office on 26th January) suggests that above-average precipitation is more probable than below-average. For February-March-April as a whole, above- and below-average precipitation are equally probable. The probability that UK-average precipitation for February-March-April will fall into the driest of five equal categories is 20% and the probability that it will fall into the wettest of the five categories is around 20% (the 1981-2010 probability for each of these categories is 20%.
River flows in January were below normal across the majority of the UK, with the exception of northern Scotland where flows were normal. Following the return of near-normal rainfall in southern England, flows in this area generally increased from December’s exceptionally low levels, however, flows were still below normal in January, and were notably low in the south-west. Notably low flows were also seen across Wales, northern England and southern Scotland.
This below normal river flows are expected to continue for the next one to three months across most of the south-east of England, despite a forecast for above average rainfall for February. Many catchments in this area are groundwater influenced, and tend to have a slow response to rainfall. In the catchments of the north and western parts of the UK, which are likely to respond more quickly to rainfall, there is considerable uncertainty in the outlook for February; however flows are most likely to be within the normal range.
Groundwater levels across the southern and eastern Chalk remained below normal for January, with notably and exceptionally low levels in central-southern England. Elsewhere, levels in the Permo-Triassic sandstones and Jurassic limestones were generally within the normal range.
Groundwater levels across the southern Chalk are likely to remain normal to below normal for the next one to three months. Groundwater levels elsewhere are expected to be within the normal range.