Quick answer: The Environment Agency published its area monthly water situation reports for August 2026 on 14 September. These are a different publication from the weekly drought bulletins, and they contain something the weeklies do not: soil moisture deficit (SMD), reported by hydrological area. The headline figures are stark. Across the Thames area SMD reached almost twice its end-of-August long-term average, with the Cotswolds East and Cotswolds West areas approximately double their respective averages. In Solent and South Downs there was “no effective rainfall across SSD and so no recharge this month”. East Anglia ended August with an SMD of 121mm, still notably high for the time of year. Even the north-west, which had near-normal August rainfall at 84% of average, recorded above-average SMD in every hydrological area but one. If you are commissioning or reviewing infiltration testing this autumn, SMD is the free, published, third-party number that tells you — and your lead local flood authority — exactly how flattering the ground conditions were on the day.
What these reports are, and why they are not the weekly bulletin
Most people following the drought have been reading the Environment Agency’s weekly dry weather and drought summaries. Those cover rainfall, river flows, groundwater classifications, reservoir stocks and area drought status. We wrote about last week’s edition, which put two monitored sites into the “exceptionally low for the time of year” class.
The area monthly reports are a separate series, published for thirteen Environment Agency areas, each with a short HTML summary and a full PDF running to twenty or thirty pages. They cover the same ground, but they add two things the weeklies leave out:
- Soil moisture deficit, in millimetres, compared against the long-term average for that area and that month
- An explicit statement on recharge — whether any effective rainfall reached the aquifer
For drainage design, those are the two most useful lines in the whole drought record.
Soil moisture deficit, in one paragraph
Soil moisture deficit is the amount of rain, in millimetres, that would have to fall to bring the soil back up to field capacity. A deficit of zero means the soil is saturated and any further rain becomes effective rainfall — it runs off, or it percolates down to the water table. A deficit of 120mm means the first 120mm of rain that falls will be absorbed by the soil profile and go nowhere near the aquifer.
That is why SMD matters to a soakaway. A trial pit dug into soil carrying a large deficit is being tested against a sponge that is nowhere near full. Water leaves the pit quickly, partly into the ground beneath and partly sideways into unsaturated soil that would not accept it in February. The measured infiltration rate is real — it just is not the rate the finished system has to work at.
What August 2026 actually recorded
The picture varies by area, and that variation is worth understanding rather than flattening.
Thames. The area received 28mm of rainfall, 45% of the long-term average, and more than three-quarters of that fell in the last week of the month. SMDs continued to increase, with the area reaching almost twice its end-of-August LTA and the Cotswolds East and West areas approximately double theirs. The report is blunt about the consequence: “Effective rainfall was negligible during the month, even in areas that would typically receive some at this time of year.”
Solent and South Downs. 42mm, 63% of the LTA. Soils in all hydrological areas ended the month drier than average despite meaningful rain after 18 August, and the report states there was “no effective rainfall across SSD and so no recharge this month.” For context on how unusual the preceding period was: April to August was the fifth driest on record for the Test Chalk hydrological area, and March to August the fourth driest for Sussex Coast, in records going back to 1871.
East Anglia. 41mm, 68% of the LTA, and the fourth driest March to August on record across the area at just 51% of average. For North West Norfolk and Wissey and for North Norfolk, that six-month period was the driest on record. End-of-August SMD was 121mm for the area, 6mm to 25mm above the LTA in most hydrological areas, and above 160mm in South Essex.
North-west England. This is the useful counter-example. August rainfall was classed normal at 84% of the LTA, and SMD decreased across every hydrological area compared with July. And yet, with the single exception of the Cheshire Rivers Group, every hydrological area still recorded higher-than-average SMD, with the highest values — 71mm to 100mm — across Lancashire and Greater Manchester, Merseyside and Cheshire. A normal month of rain did not undo a dry spring and summer. Reservoir storage tells the same story: down from 66.7% to 50.8% over the month, against an average of 71.7%.
The pattern across all four is the same. A wetter fortnight moved river flows. It did not refill soils, and it did not start recharge.
Why “no recharge in August” is not, on its own, alarming — and why it still matters
Recharge is not supposed to happen in August. In a normal year, evapotranspiration takes everything the summer delivers, the deficit builds through the warm months, and the aquifer year begins somewhere around October or November once the soil has been rewetted and rain finally gets past it.
So the finding is not that recharge failed. It is where the deficit sits at the point recharge is due to begin. A soil profile entering October carrying close to double its normal deficit needs that much more rain before the first millimetre reaches the water table. The recharge season does not start on a date. It starts when the soil lets it — and this year the soil will let it later.
For a drainage designer, that has a narrow, practical consequence. The gap between the conditions you can test in during September, October and November, and the conditions the system has to perform in, is wider this year than the seasonal-correction rules of thumb assume.
What to do with the number
None of this is an argument against testing. It is an argument for writing down what you tested into.
Quote the SMD in the report. The area monthly report for the month your test was taken is a free, dated, third-party publication from the regulator. A single line — the area, the month, the SMD in millimetres and its relationship to the long-term average — converts “the test was taken in a dry period” from an assertion into a citation. It costs one sentence.
Say whether recharge had begun. Where the report states there was no effective rainfall, say so. An LLFA officer reading an infiltration rate measured in a month the Environment Agency has formally recorded as producing no recharge will draw the right conclusion either way. Better that you drew it first.
Keep the design water table separate from the observed one. This is the point we made last week and it has not changed: the water table in your trial pit is close to its annual minimum, and the separation distance applies to the highest expected groundwater level, not the one you happened to measure. SMD is evidence about the rate; groundwater classification is evidence about the level. You need both.
Watch the regional variation rather than assuming the national headline. North-west England had a normal month of rain and still carries an above-average deficit. Thames had a poor month and carries close to double. The Cheshire Rivers Group is, on this measure, back to normal. “There is a drought” is not a design input. The SMD for your specific hydrological area is.
And remember the rule of three fills cannot rescue you. BRE Digest 365 requires three successive fills and the slowest result, which controls for the pit wetting up over the course of a test. It does not control for a soil profile carrying a 120mm deficit before you started, because all three fills happen into the same dry ground.
The short version
The Environment Agency now publishes, every month and for free, the one variable that explains why a drought-season soakage test reads high — and for August 2026 that variable sits near double its average across the Thames area, above average almost everywhere else, and with recharge formally recorded as absent in southern England. Use it. A drainage strategy that cites the soil moisture deficit for the month of the test is considerably harder to argue with than one that does not mention conditions at all.
SoakMonkey will take your BRE Digest 365 test results and produce a printable soakaway design for the drainage strategy. The seasonal judgement — what the test would have shown in February, and what you assumed about it — still belongs in your report, in your words, with the evidence attached.
Sources: Water situation: area monthly reports for England (Environment Agency, updated 14 September 2026) · Thames water situation: August 2026 summary · Solent and South Downs water situation report: August 2026 summary · East Anglia water situation: August 2026 summary · North-west England water situation: August 2026 summary · Water situation reports for England (collection)