August 2013


Summary

River flows in August are likely to be in the normal range across much of Great Britain, but with an increased likelihood of below normal flows in southern Britain and northwest Scotland, and above normal flows in some central and northern areas. Across all aquifer areas, groundwater levels are likely to be normal or moderately above in August. All sources of information suggest that the current water resources situation is unlikely to change substantially over the next three months. 

Rainfall

The balance of probabilities suggests that the dry, settled conditions experienced in July may not persist through August; currently near-to-above-average rainfall is slightly favoured. For August-September-October as a whole the signal is largely indistinguishable from climatology. The probability that UK precipitation for August-September-October will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is around 20% (the 1981-2010 probability for each of these categories is 20%).Click here for more detailed information on the Met Office long-term forecast. [rainfall outlook based on Met Office forecast issued 5 Aug 2013] 

River flows

July river flows were mostly in the normal range or below, with the lower flows being in catchments in Wales, southwest England, parts of East Anglia and the north of Scotland. Above average flows occurred in parts of central England, in response to rainfall late in July. (click here For further information on the situation in July). The one-month-ahead outlook suggests August river flows are likely to be in the normal range or below across southern Britain and northwest Scotland, and in the normal range or above in northern England and southern Scotland. Historical analogues indicate that the above-normal flows seen in July in some catchments in central England may persist into August. The model-based assessments and the historical analogues approaches are both suggestive of stability in river flows over the next three months, with projections favouring flows being in the normal range across much of Great Britain. For full information on the river flows outlook, click here.

Groundwater

July groundwater levels were normal in most aquifers, and above in parts of the Chalk and Permo-Triassic, exceptionally so in some northern boreholes. (click here For further information on the situation at the end of July). August groundwater levels are likely to continue to recede, even if the month is very wet, so the outlook is for groundwater levels for August to be normal in most aquifer areas, and moderately above in parts of the Chalk and the Permo-Triassic limestones (reflecting recent observed trends). The three-month ahead outlook is also suggestive of groundwater levels being in the normal range or above for most aquifers, with a greater likelihood of above average levels in the Chalk of the Chilterns and East Anglia, and the Permo-Triassic of the northwest.  For full information on the groundwater outlook, click here.