December 2016


Period: From December 2016      Issued on 09.12.2016 using data to the end of November 2016

Summary

The outlook for both December and the next three months is for normal to below normal groundwater levels in most of the major aquifers, although the signal for below normal is weaker over the longer timeframe. Away from southern England, groundwater levels are likely to show regional differences over both one and three months. The December-February outlook for river flows indicates that flows are likely to be normal to below normal for the south-east of the UK and within the normal range elsewhere. The one month outlook for river flows is less certain, particularly in western parts of the UK, although flows within the normal range are most likely in southern and eastern areas

Rainfall

Although most of England received above average rainfall in November, the majority of this fell over a few days midmonth and the rest of the month was relatively dry. Rainfall totals were below average for Scotland, Wales and Northern Ireland. Persistent high pressure over the last 10 days of the month meant very little rainfall was registered over this timeframe.

The rainfall outlook for December (released by the Met Office on 24th November 2016) is that below-average precipitation is more likely than above-average. For December-January-February as a whole there is only a slight shift from the normal range of expected conditions, with below-average precipitation slightly more probable than aboveaverage. The probability that UK-average precipitation for December-January-February will fall into the driest of five equal categories is between 20% and 25% and the probability that it will fall into the wettest of the five categories is around 15% (the 1981-2010 probability for each of these categories is 20%).

River flows

Average river flows for November were below normal across northern and western parts of the UK, notably so in south Wales and parts of Scotland. Further south and east, river flows were generally within the normal range.

The outlook for December is for river flows to be in the normal range across most of the UK. However, there is considerable uncertainty in the outlook for western parts of the country. Despite recent low rainfall, some notably low river flows and a below average rainfall forecast, there is not a strong signal for continued below normal flows in this generally wetter and more responsive region. Over the next three months, the outlook is for normal to below normal river flows across the south-east of the UK and for flows to be predominantly in the normal range elsewhere. The same normal to below normal signal for river flows in the south-east is also apparent in the outlook for the next six months.

Groundwater

Groundwater levels in the Chalk were predominantly in the normal range or below in November, with below normal levels in Yorkshire and the responsive aquifers of Northern Ireland and central southern England. In the other major aquifers of the UK, groundwater levels were mostly in the normal range with some localised above normal exceptions.

The outlook for December is for a continuation of normal to below normal groundwater levels in the Chalk of southern and eastern England. Below normal levels are particularly likely in responsive aquifer units in central southern England. For the Permo-Triassic sandstones of the West Midlands, the outlook is for above normal levels over the next month. Similar to the December outlook, the three-month outlook for the Chalk is also for normal to below normal levels, although the below normal signal is slightly weaker over December-February. Groundwater levels in southern Scotland and north-west England are likely to be normal to above normal over the next three months.

Further information - December 2016

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