The one month outlook is for river flows to be below normal in the south-east of the UK, and possibly notably low in groundwater fed catchments. These low flows are likely to persist into the autumn. Elsewhere river flows are likely to be in the normal to above normal range both in July and for the coming three months. Much the same regional variation is expected in groundwater levels with the south-east experiencing low to notably low levels until the autumn. In other parts of the UK groundwater levels are most likely to be in the normal range with the exception of aquifers in the border region of Scotland where groundwater levels will remain above normal.
Rainfall during June showed marked regional variation with Scotland, northern England, Wales and south-west England having above average rainfall, and central England receiving below average rainfall.
The Met Office 3-month Outlook issued on 22nd June said that for July and July-August-September above-average precipitation is slightly more probable than below-average.
The probability that UK precipitation for July-August-September will fall into the driest of our five categories is between 15% and 20% and the probability that it will fall into the wettest of our five categories is around 20% (the 1981-2010 probability for each of these categories is 20%).
June river flows showed marked regional differences. In Scotland, Northern Ireland, northern England, and Wales river flows were generally above average. Elsewhere river flows were normal to below normal, with lower flows being more widespread towards the south. The south-west of England experienced a wide range of river flows.
With an outlook for above average rainfall to be slightly more likely than below average rainfall, river flows to north and west will be in the normal to above normal range in July and the next three months. Even with above average rainfall, river flows in south-eastern areas are likely to remain below normal in July and until the autumn. Flows in rivers that are largely fed from groundwater could be notably low.
Groundwater levels were in the below normal to notably low range in the Chalk aquifers of southern England during June. Elsewhere groundwater levels were normal to below normal apart from in the Permo-Triassic sandstones of southern Scotland, where levels were above normal.
During the summer months any increase in groundwater levels is extremely unlikely even with above average rainfall, and so the current pattern of groundwater levels is likely to persist through the next three months and until the start of the autumn recharge. While there is uncertainty over the timing of autumn recharge it is likely that low groundwater levels will persist in places over at least the next six months. It is possible that in some isolated aquifers groundwater levels will reach exceptionally low levels during this period.