Wednesday, 15 July 2015

June 2015 overview

Groundwater levels, June 2015
Overall, June was dry, especially in parts of south-east England, and sunnier than average. With dry conditions over the main outcrop areas, particularly in the far south-east, and some notably warm spells later in the month, by the end of the month soil moisture deficits (SMDs) climbed to well above the average for late June. Correspondingly, groundwater levels in all indicator wells fell during June as would be expected at this time of year, when any rainfall is likely to be lost as evapotranspiration.

In the Chalk the pattern established in recent months continued. Levels were above normal for the time of year at Little Bucket Farm (Kent), but generally levels were normal or below, with below normal levels in western parts of the aquifer (Wessex and western parts of the South Downs) and parts of East Anglia and Yorkshire. Ashton Farm in Wessex recorded its fifth lowest June average level in a 42 year record. 

In the Magnesian and Jurassic limestone aquifers levels were either normal or below, and levels in the Carboniferous Limestone of South Wales and Derbyshire remained in the normal range.  

Groundwater levels at Newbridge in the Permo-Triassic Sandstones
In the Permo-Triassic sandstones, levels were average or well above; Nuttalls Farm in the West Midlands saw exceptionally high levels while Newbridge (south west Scotland) reached a record high for June (see hydrograph).  These aquifers respond slowly to changes in rainfall, and the latter is located in an area that has seen moderately above-average rainfall over recent months.

For more information, see the Hydrological Summary for June 2015 [PDF].

Tuesday, 14 July 2015

Hydrological Outlook from July 2015

The latest Hydrological Outlook is available.
Hydrological Outlook for July 2015

The latest predictions for UK precipitation favour near- or below-average rainfall during July and for July-August-September as a whole.

Groundwater levels in June exhibited a very similar pattern to recent months: below normal levels in parts of the southern and eastern Chalk contrasted with normal levels elsewhere in the aquifer.  Levels in other aquifers were mostly normal or below, except in some Permo-Triassic boreholes where exceptionally high levels persist. 

This pattern is likely to continue through July, with recessions largely unaffected by summer rainfall. Over the three month timeframe (Jul-Sep), model projections suggest that groundwater levels in some areas with below normal levels may be trending towards the normal range. However, analysis of historical analogues suggests that this may be unrealistic and that below normal levels in Wessex and the Yorkshire Chalk are likely to persist into early autumn. The onset of the recharge season is likely to be delayed in areas in which below normal levels persist in the longer term.

For further information see the full Hydrological Outlook for July.