Quick answer: The Environment Agency’s report for 4 to 10 September 2026, published on 11 September, records a second consecutive wetter week — 14mm in east England to 46mm in the north-west — and the seasonal groundwater recession continuing “at almost all sites”. Two sites are now classed exceptionally low for the time of year: Tilshead in the Upper Hampshire Avon Chalk, and Jackaments Bottom in the oolite limestone of the Cotswolds. Reservoir storage fell again to 56.9%, 19.7% below average, with 12 reservoirs or reservoir groups under half full and eight classed exceptionally low. The ten areas in drought stayed in drought. If you are about to commission infiltration testing for a SuDS design, the water table you measure this month is close to the annual minimum — and that is not the number a soakaway has to work at.
What the report says
England had a second wetter week, but not a transformative one. Rainfall ranged from 14mm in east England to 46mm in the north-west. After the first eight days of the month England had received 33% of the long-term average for September — 27% in the north-east, 45% in the north-west.
Rivers responded at just over half the monitored sites. Even so, 23 sites (42%) are classed normal for the time of year, 11 (20%) below normal and 7 (13%) notably low.
Groundwater did not respond at all. The Environment Agency records that “the seasonal recession of groundwater levels continued at many sites across England, with levels decreasing at almost all sites.” Every chalk aquifer site is normal or lower. Four sites in the Wessex Downs, Yorkshire Wolds and the North and South Downs are notably low. And two have dropped a class further:
- Tilshead, in the Upper Hampshire Avon Chalk — exceptionally low for the time of year
- Jackaments Bottom, in the oolite limestone of the Cotswolds — exceptionally low for the time of year
In the north-west, Skirwith in the Carlisle Basin and Eden Valley Sandstone is classed below normal.
Reservoirs kept falling. Storage for England was 56.9% in the week ending 8 September — 19.7% below average — down from 58% the week before. Twelve reservoirs or reservoir groups are now under half full, up from eleven. Only Vyrnwy and Draycote are classed normal for the time of year. Eight are exceptionally low: Ardingly, Clatworthy, Clywedog, the Dove Group, Rutland Water, Hanningfield, Haweswater and Thirlmere, and Wimbleball.
Area drought status did not move. Ten areas remain in drought — East Anglia, Hertfordshire and North London, Thames, Devon Cornwall and Isles of Scilly, West Midlands, Wessex, Kent and South London, Solent and South Downs, East Midlands, and Lincolnshire and Northamptonshire. The remaining four are in prolonged dry weather. Temporary use bans still cover 30 million people across ten water companies, and Wessex Water has moved into drought level 1b.
Why “exceptionally low” in September matters more than it sounds
Groundwater in England is supposed to be low in September. The recession runs through the summer as evapotranspiration takes everything the rain delivers, and the water table bottoms out somewhere around late September to October before the recharge season begins. A low reading now is normal.
The classification is not a reading. It is a comparison against the historic range for that site at that time of year — so “exceptionally low for the time of year” means the level is unusually low even measured against other Septembers. At Tilshead and Jackaments Bottom, the water table is not just at its seasonal floor. It is below where the seasonal floor has historically sat.
That matters for two reasons.
It sets the starting point for recharge. Aquifers refill from where they are. A chalk or limestone aquifer entering October from an exceptionally low base needs an above-average winter simply to reach a normal spring. The Environment Agency has asked water companies for updated autumn and winter projections, to be discussed at the National Drought Group on 15 September — which is the meeting worth watching, because it is the first formal read on whether this drought ends in 2027 or carries into it.
And it makes September and October the most misleading months of the year for infiltration testing.
The soakaway problem, stated plainly
An infiltration test measures how fast water leaves a trial pit. What it does not measure is the condition the finished system has to work in.
Two things are wrong with a test taken now:
The infiltration rate is flattering. Dry ground with a deep unsaturated zone takes water quickly. The same pit in February, with the water table up and the soil profile wet, will not. BRE Digest 365’s rule of three fills, taking the slowest, controls for short-term antecedent conditions — but it cannot control for a multi-year drought, because all three fills happen in the same dry week.
The water table is at its annual minimum. Standard practice — and the expectation behind BRE Digest 365 and the SuDS Manual — is that the base of an infiltration system sits clear of the highest expected groundwater level, with one metre the separation commonly applied and commonly asked for by lead local flood authorities. A trial pit dug at the seasonal floor of an exceptionally low year will show a water table that is metres deeper than the level the design actually has to respect. Read that depth as the design condition and you can end up with a soakaway base sitting inside the winter saturated zone of a normal year.
Neither of these is a reason not to test. They are reasons to be explicit about when the test was taken and what you assumed about seasonal variation.
What to do about it
Date-stamp the test and say what the conditions were. A soakage test report submitted with a planning condition discharge or a Building Regulations application should record the date, the antecedent rainfall and the measured groundwater level. An LLFA officer reading a test dated September 2026 in a catchment that has been in drought since 2025 will want to know you noticed.
Do not take the observed water table as the design water table. Establish the highest expected groundwater level from a source that is not a single September pit — long-term monitoring data, the British Geological Survey’s records, borehole logs from the site investigation, or seasonal monitoring across the winter. Then apply the separation distance to that level.
Where the design is marginal, monitor through the winter. If the scheme only works at the infiltration rate a drought-season test produced, it does not work. Winter monitoring costs a few months. Redesigning surface water strategy after a refusal, or after a system fails in its first wet winter, costs considerably more.
Expect the LLFA to be sceptical. Lead local flood authorities have spent two summers looking at test results taken in the driest conditions in the record. The ones that scrutinise seasonal correction are not being awkward — they are applying the national SuDS standards that the 2026 NPPF now points planning policy towards.
And keep the water efficiency evidence tidy. The same drought that is depressing the water table is the backdrop to Part G’s 105 litre standard and to local planning policies pushing below it. Temporary use bans covering 30 million people are not an argument that will be made to you — but they are the reason the fitting schedule on a new dwelling is being read more carefully than it was three years ago.
The wider numbers, for context
Agriculture has passed peak irrigation, but 549 abstraction licence restrictions remain, alongside 1,094 voluntary restrictions cutting abstraction by 50% across the Thames, Wye and Severn catchments. Formal section 57 restrictions continue in parts of East Anglia until 31 October.
Environmental damage is still accumulating: 330 confirmed drought and dry weather incidents since the start of 2026, against 288 at the same point in 2025. Fish death incidents rose by 19 in a single week to 70. Blue-green algae continues to affect a 10km stretch of the Lower Thames, including the Ham and Kingston bathing water.
And three drought orders and permits are live: the River Severn Drought Order (applied 17 August, appeals hearing 3 September, decision imminent), Southern Water’s River Test order awaiting a Secretary of State decision, and South East Water’s River Ouse drought permit application of 28 August.
The short version
A wet fortnight has changed river flows and changed very little else. Groundwater is still falling, two monitored sites have fallen out of the bottom of their historic range for September, and the recharge season is about to start from a worse position than last year’s. For anyone producing drainage evidence this autumn, the practical consequence is narrow and specific: treat an infiltration test taken in the next eight weeks as a best case, not a design case.
SoakMonkey will run BRE Digest 365 from your test results and produce a printable design for the drainage strategy. What it cannot do is tell you whether the water table you measured in September is the one the soakaway has to live with in February — that judgement has to be made, recorded, and defended in the report.
Sources: Dry weather and drought in England: 4 to 10 September 2026 (Environment Agency, 11 September 2026) · Dry weather and drought in England 2026: summary reports (collection) · Water situation reports for England (Environment Agency) · Drought: how it is managed in England (Environment Agency)