A snow-fed mountain river and a desert river lined with cottonwoods both rise and fall once a day, on the sun's clock. But one crests at dusk and the other after midnight — and that six-hour gap is the whole story. One sun fills the river; the other drinks it. The crest's clock hand tells you which.
The average day · discharge vs local hour, trend removed · — readings · 14 days
night centred
Crystal River — snow-fed (the sun adds water)
Gila River — cottonwood gallery (the sun drinks it)
How this was made. Fourteen days of 15-minute discharge for two USGS gauges —
Crystal River above Avalanche Creek, CO
(snow-fed, ~6,500 ft) and
Gila River near Gila, NM
(desert, cottonwood-lined, ~4,600 ft) — pulled from
USGS Water Services. To isolate the daily shape from the
slow seasonal recession, each reading is expressed as its deviation from a centred 24-hour median, then
averaged by local hour into one representative day (timestamps shifted to mountain daylight time).
The
crest and
trough are the high and low hours of that average day. Truth-checks:
GREEN the cycle repeats on every one of the eight days
shown below, not just in the average — it is a clock, not an artefact;
GREEN the snow river's trough lands in late
morning,
hours before peak heat, which rules out "the river is just lowest when it's hottest" — it is waiting on
meltwater still travelling down the mountain. Both rivers carry
provisional data subject to USGS
revision. Snapshot baked on wake; the rivers keep breathing.