October 2017


Period: From October 2017      Issued on 09.10.2017 using data to the end of September 2017

Summary

River flows are likely to be normal to above normal across most of the UK during October, with above normal flows most likely in the north-west of the UK. Only in parts of south-east England are flows likely to be normal to below normal in October, and in this area flows are likely to remain in this range for the next three months. Elsewhere there is considerable uncertainty concerning river flows over the next three months. Groundwater levels are likely to be normal during October with the exception of parts of south-east England, in which below normal levels are most likely, and in southern Scotland, where above normal levels are likely to continue in October.

Rainfall

Rainfall during September was spatially variable but much of the country saw above average rainfall (the UK rainfall was approximately 120% of average). The main areas with below average rainfall were south-east England, and north-west and central Scotland.

The Met Office 3-month Outlook issued on 28th September indicated that for October and October-November-December above-average precipitation is more probable than below-average precipitation.

The probability that UK precipitation for October-November-December will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest of our five categories is around 30% (the 1981-2010 probability for each of these categories is 20%). 

River flows

There was great variation in river flows during September with notably high flows in many rivers in south-west England, Wales, Northern Ireland and north-east Scotland. Elsewhere flows were generally normal except for parts of south east England where there were below normal flows.

While normal to below normal flows are likely to persist in south-east England, elsewhere flows are expected to be normal to above normal, with above normal flows most likely in the north-west of the UK.

Groundwater

Groundwater levels were normal to below normal in most parts of the UK during September, but above normal in west Wales, Northern Ireland and southern Scotland.

Over the next month a continuation of mixed levels in the Chalk aquifer is likely. Responsive parts of the aquifer, especially in the south and west will trend towards normal, or even above normal levels in some locations, but slower responding parts of the aquifer will continue to exhibit low levels in Kent and north of London. In the Yorkshire Chalk and Midland aquifers levels will be normal, with higher levels further north. Over 3 months the outlook is for normal to above normal levels in most aquifers, apart from the slowly responding Chalk.

Further information - October 2017

Comprehensive further information that supports the production of the Hydrological Outlook UK is available here.