The two Augusts that drew the same line, 43 feet apart

The same data on a warm off-white page, kicked “The same two Augusts · one fixed ruler, 600–720 ft, on every panel” and headlined “The two Augusts that drew the same line were 43 feet apart.” A standfirst says each postcard was fitted to its own month, so each spent its whole height on the summer dip and none of it on where the water stood; for a well, where the water stands is the news, and on one fixed scale the dips shrink to ripples and the 43-foot drop between them is the picture. The left panel, “Every daily reading since November 1932”, plots the daily highs as a thin grey line, broken at gaps of more than three days, on a 600 to 720 ft axis ticked every 20 ft, with years 1940 to 2020 along the bottom. The line swings between roughly 625 and 700 ft for most of the century, with a deep trough to the record low, 612.5 ft on 17 August 1956, and a peak at the record high, 703.3 ft on 14 June 1992. Two dashed rules start in 2007 and are labelled at the right “today’s triggers, drawn from 2007”: “Stage 1 · 660” and “Stage 4 · 630”. August 1993 is a short thick blue mark high in the 1990s, with an angled leader to the label “August 1993 · averaged 674.0 ft”; August 2024 is a short thick orange mark near the bottom of a sag after 2020, around the 630 line, labelled “August 2024 · averaged 631.0 ft”. The right panel, “The two postcards, on that same ruler”, draws both months on the same 600 to 720 ft scale, 1 to 31 August, with the dashed Stage 1 and Stage 4 rules and a thin solid line labelled “median August, 655.7”. The blue 1993 line runs from 678 down to 672 well above the median, labelled “moved 6.4 ft all month”; the orange 2024 line runs from 636 down to 628 well below it, crossing the 630 rule, labelled “moved 8.4 ft · daily high under 630 on 15 days”. Both are almost flat. Short ticks at the right edge mark the two month averages, “avg 674.0” and “avg 631.0”, joined by a double-headed arrow labelled “43.0 ft · 5.2× the larger month’s whole move”. Footnotes say each postcard’s height was worth 6.4 ft in 1993 and 8.4 ft in 2024, and where the water stood was on neither; that every panel here uses one 600–720 ft scale; that the median August is the median of 87 complete Augusts’ averages; that the triggers are today’s EAA San Antonio Pool levels, applied to a 10-day average alongside springflow triggers, and that a 10-day average of these highs was under 630 from 22 to 31 August 2024; and credit the Edwards Aquifer Authority’s J-17 San Antonio Pool Index daily high water level, 12 November 1932 to 13 October 2026, provisional from 1 October 2026, retrieved 15 October 2026, with the drawing ours. — Showing the misleading chart

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A newsletter widget we invented draws a monthly postcard of the Edwards Aquifer’s J-17 index well, its axis fitted to that month’s own readings. Asked for August 1993 and August 2024, it draws the same picture twice: a gentle summer dip. But the 1993 water averaged 674.0 ft above sea level and the 2024 water 631.0 ft, 43.0 ft lower, with the daily high under the 630 ft Stage 4 drought line on 15 of its 31 days. Neither postcard can show that, because each drew its month around its own middle.

Edwards Aquifer Authority, J-17 San Antonio Pool Index well (J17WL, USGS 292845098255401), daily high water level elevation, 12 November 1932 – 13 October 2026, retrieved 15 October 2026. Critical-period trigger levels as summarised at edwardsaquifer.net (“Drought restrictions”). The newsletter, the widget and both drawings are ours., 2026Added October 15, 2026

01The claim

Thirty-one Augusts apart, the San Antonio index well drew the same gentle summer dip, so the old well is doing just fine.

02The trick

Every reading on both postcards is real and neither line is bent. What makes them twins is that each card’s vertical axis runs from that month’s lowest daily high to its highest, which is what most chart tools do when nobody sets a range. Any month drawn that way fills its box from corner to corner. Usually the warning about this kind of axis is that it inflates a small wiggle. Here the bigger loss is the level. A fitted axis is recentred on every window as well as resized, so it keeps the shape of each month and throws away where the month sat. The cards even print the evidence, small and grey at the ends of each axis: 671.7 to 678.1 ft in 1993, 627.8 to 636.2 ft in 2024. August 1993 averaged 674.0 ft above sea level and August 2024 averaged 631.0 ft. That is 43.0 ft lower, more than five times the whole movement of either month, and neither postcard can show it, because each drew its month around its own middle. For a well, that gap is most of the story. The EAA’s drought stages for the San Antonio Pool are set partly in J-17 feet (alongside springflow at Comal and San Marcos Springs): on a 10-day average, Stage 1 begins below 660 ft and Stage 4 below 630. In August 2024 the daily high was under 630 on 15 of the 31 days. In August 1993 it never came within 11 ft of 660. A summer dip is the one thing the two months had in common, so it is the only thing the postcards could draw. The two years are not the extremes: August 1993 sits in the top fifth of the record, and the 2024 average is a few feet above August 2023’s. (The Well-Wisher, its widget and both captions are our invention; the readings are the Edwards Aquifer Authority’s.)

03The fix

The redraw holds one scale, 600 to 720 ft, wide enough for the whole 94-year record, on both panels, and adds lines that never move: today’s Stage 1 and Stage 4 triggers, drawn only from 2007 when the 660 ft level was set, and the median August, 655.7 ft. On that scale the postcard dips shrink to ripples of 6.4 and 8.4 ft. August 1993 sits 18 ft above the median, a year after the record high of 703.3 ft in June 1992. August 2024 sits 25 ft below the median, on the Stage 4 line, in a dry spell that reached 623.1 ft in May 2025, the lowest since 1990. The 43-foot gap between them is now the biggest thing in the picture. Where a widget has to follow the data, pin it to something that holds still, such as a trigger line or a long-run median, and print the level next to the shape. “631.0 ft · 25 ft below a typical August” would have fit on a postcard.