PRE-ANALYSIS (per-gauge facts, all timestamps CDT):
| Gauge | (a) First | (b) Max | (c) Last | (d) Intraday low | (e) Low→peak rise |
|---|---|---|---|---|---|
| Boxley | 3.39 ft @00:00 | 3.39 ft @00:00 | 2.96 ft @22:30 | 2.96 ft @22:30 | none — monotonic fall (pool drain) |
| Ponca | 579 cfs @00:00 | 579 cfs @00:00 | 319 cfs @23:15 | 319 cfs @23:15 | none — monotonic fall |
| Pruitt | 6.75 ft / 1290 cfs @00:00 | 6.75 ft / 1290 cfs @00:00 | 5.44 ft / 688 cfs @23:15 | 5.44 ft / 688 cfs @23:15 | none — monotonic fall |
| St. Joe | 11.86 ft / 8740 cfs @00:00 | 11.86 ft / 8740 cfs @00:00 | 8.38 ft / 3700 cfs @22:45 | 8.38 ft / 3700 cfs @22:45 | none — monotonic fall |
| Harriet | 13.28 ft / 13200 cfs @00:00 | 13.28 ft / 13200 cfs @00:00 | 8.18 ft / 4800 cfs @23:45 | 8.18 ft / 4800 cfs @23:45 | none — monotonic fall |
| Richland | 3.63 ft @00:00 | 3.63 ft @00:00 | 2.75 ft @23:00 | 2.74 ft @22:30 | +0.01 ft (noise) |
| Bear Cr | 3.97 ft / 679 cfs @00:00 | 3.99 ft / 698 cfs @00:15 | 3.33 ft / 264 cfs @23:15 | 3.33 ft / 264 cfs @23:15 | +0.02 ft @00:15 (recession wobble, QPE=0) |
(f) QPE-peak timing: Today's basin QPE is 0.000" everywhere — no rainfall-attributable responses exist today. Every gauge is in pure recession from the Event-20 flood (peaks Day 106). No new lag computation is possible; all values below are recession-rate (dQ/dt) observations, not rainfall pairs.
Zero QPE basin-wide (all 37 HUC12s report 0.000" 24-hr). This is a clean recession-only / flood-limb day — the most valuable high-flow recession dataset of the study. 7-day antecedent totals remain at study-high saturation (Cove 5.11", Headwaters Richland 4.92", Headwaters Bear 4.93", St. Joe sub-zones 3.3–4.9") from the Event-20 deluge.
Every gauge fell monotonically all day — pure recession from Event 20. Key values:
None — QPE is 0.000" basin-wide. No transfer ratios or lags computable today. (Per auto-context, all rises belong to the Day-105/106 Event-20 forcing already analyzed.)
No new propagating pulse today. The Event-20 mainstem cascade already peaked (St. Joe 08:00 Day 106 → Harriet ~13:30–14:30 Day 106, the confirmed ~6–6.5 hr flood-flow lag). Today St. Joe and Harriet recede in parallel. Note the persistent limb offset: late-day St. Joe ~103 cfs/hr at 3700 cfs vs Harriet ~135 cfs/hr at 4800 cfs — Harriet falls faster in absolute terms because it peaked ~6 hr later and sits higher on its limb. This is the same flow-level/limb-position offset documented in the Days 102–104 tail, now reproduced at flood scale.
Today delivers the steepest, highest-flow recession series of the study (Open Q11). High-flow dQ/dt-vs-Q points, St. Joe: - Near peak (yesterday, Day 106): ~700 cfs/hr at 10,000–19,000 cfs - Today early (~8000 cfs, 00:00–02:00): ~415 cfs/hr - Today late (~3800 cfs, 21:00–22:45): ~103 cfs/hr
Harriet: - Today early (~12,500 cfs, 00:00–02:00): ~700 cfs/hr - Today late (~5000 cfs, 21:00–23:45): ~135 cfs/hr
These bracket the curve between yesterday's flood-limb (~700 cfs/hr) and the Event-19 interflow tail (~32 cfs/hr at 1300–2500, Day 102) down to baseflow (~10–15 cfs/hr). The dQ/dt-vs-Q relationship is now populated across nearly two orders of magnitude in Q — a strong nonlinear storage-discharge curve. In stage terms St. Joe fell ~0.255 ft/hr early (11.86→11.35) decaying to ~0.09 ft/hr late; Harriet ~0.375 ft/hr early to ~0.07 ft/hr late.
Optimal-window watch: Both St. Joe and Harriet re-entered Optimal today and remain mid-range at day's end (St. Joe 3700 cfs, Harriet 4800 cfs). Given the flood magnitude, expect a multi-day-to-multi-week Optimal window on the lower mainstem — consistent with Event 15+16 (~15+ days) and Event 19 (≥6 days). Ponca trending toward first exit again.
None. Today is textbook flood-limb recession with zero forcing — exactly what the post-Event-20 watch (Open Q12) called for. The Bear Cr 00:15 +0.02 ft wobble is within karst/measurement noise (QPE=0) and should not be read as a pulse. No USGS rating-curve step changes detected today at any gauge despite the record event — high-stage curves continued to track smoothly through the entire recession (no discrete cfs jumps in Bear/Richland/Pruitt), which is worth a field-revision watch over the next several days as USGS typically visits after record floods.