No new precipitation anywhere in the watershed today. All 37 HUC12s recorded 0.00" for the 24-hour period. The 7-day antecedent totals remain elevated from Event 2 (March 7), now ranging from 1.66" (Headwaters Big Creek) to 3.87" (Cove Creek), with the Ponca and Pruitt zones showing the highest accumulations (Whiteley Creek 3.56", Cove Creek 3.87", Beech Creek 3.00").
Note on DST transition: Timestamps shift from CST (-06:00) to CDT (-05:00) partway through the day, with a gap visible in the data between ~01:45 CST and 03:00 CDT. This is the spring-forward clock change and does not represent missing data — roughly one hour of wall-clock time was lost.
This is a pure recession day — all gauges are falling from Event 2 with no new forcing. This makes it an excellent opportunity to characterize recession behavior.
St. Joe — THE major story today. The rapid rise that was underway at EOD March 7 (5.63 ft / 1,150 cfs) continued into the early hours of March 8: - Rose from 5.63 ft at 22:45 on 3/07 to 8.01 ft at ~04:15-04:30 CDT (peak), a further 2.38 ft rise overnight. - Peak discharge: 3,230 cfs at 04:15-04:30 CDT. - Total rise from pre-event baseflow: 4.60 ft (3.41 → 8.01 ft), 3,077 cfs (153 → 3,230 cfs), +2,012%. - Now in slow recession: 8.01 ft → 6.58 ft (1.43 ft drop through EOD), 3,230 → 1,860 cfs. - Recession rate: fairly linear, ~0.07 ft/hr average, ~70 cfs/hr. - At EOD still at 6.58 ft / 1,860 cfs — well within Optimal range (200-8,000 cfs) but still extremely elevated above baseflow (12x).
Harriet — Dramatic surge today, clearly the Event 2 flood wave arriving: - Started the day at 3.84 ft / 315 cfs (already slightly elevated from early Event 2 response). - Rose slowly until ~06:30 CDT (4.12 ft), then accelerated sharply. - Peak rise rate: 0.99 ft/hr at 09:15 CDT — the fastest hourly rise observed at any gauge in the study. - Peak: 6.83 ft / 3,050 cfs at ~12:30 CDT. - Total rise: 2.99 ft (3.84 → 6.83 ft), 2,735 cfs (315 → 3,050 cfs), +868%. - Now receding: 6.83 → 6.26 ft at EOD, 3,050 → 2,390 cfs. - Still well within Optimal range (200-9,370 cfs).
Pruitt — Steady recession throughout: - 6.24 ft / 1,010 cfs → 5.21 ft / 556 cfs (−1.03 ft, −454 cfs). - Smooth exponential decay, ~0.04-0.05 ft/hr. - Still in Optimal range (>200 cfs).
Ponca — Steady recession: - 413 cfs → 277 cfs (−136 cfs). - Now in Optimal range (200-1,600 cfs), approaching Low but Floatable boundary.
Boxley — Slow recession: - 3.13 ft → 2.88 ft (−0.25 ft). Very steady ~0.01 ft/hr. - Still ~1 ft above pre-event baseflow (1.90 ft), indicating significant subsurface drainage continuing.
Richland Creek — Recession: - 2.39 ft → 2.05 ft (−0.34 ft). Still well above baseflow (0.93 ft).
Bear Creek — Slow recession: - 2.91 ft / 48.6 cfs → 2.76 ft / 33.5 cfs (−0.15 ft, −15.1 cfs). - Much slower recession than Richland, consistent with larger watershed draining more gradually.
No new rainfall today, but we can now complete the Event 2 analysis with the full St. Joe and Harriet responses.
Event 2 — St. Joe (COMPLETED): - Peak QPE in St. Joe zone: 1.358" average across 14 HUC12s, with highest in Shop Creek (1.868"), Big Creek-Buffalo (1.661"), Lick Creek (1.642"), Left Fork Big Creek (1.615"). - Rain fell primarily between 05:00-13:00 UTC on March 7 (23:00 CST March 6 to 07:00 CST March 7). - St. Joe peak at ~04:15-04:30 CDT March 8 = ~03:15-03:30 CST March 8. - Lag from centroid of St. Joe zone rainfall (~04:00 CST March 7) to St. Joe peak (~03:30 CST March 8) ≈ 23.5 hours. - But this includes both local tributary response time AND mainstem propagation from Pruitt. The St. Joe response is a composite signal.
Signal separation for St. Joe — Richland gauge check: - Richland Creek rose from 1.16 ft to 2.55 ft peak (~16:15 CDT March 7), now receding to 2.05 ft. - Richland received 1.24" average. Its response confirms rain WAS in the Richland sub-basin. - The St. Joe rapid acceleration starting ~19:00 CST on March 7 (the 0.70 ft/hr surge) began well AFTER Richland peaked, suggesting this surge was primarily the Pruitt pulse arriving, not local Richland input. Richland was already in recession by then. - The further rise to 8.01 ft overnight (March 7-8) reflects the continued arrival of the Pruitt flood wave combined with the sustained drainage from the large St. Joe tributary complex (Little Buffalo, Big Creek, Cave Creek all received 0.8-1.9").
Event 2 — Harriet (COMPLETED): - Harriet zone received 1.071" average. Bear Creek received 1.199". - Bear Creek gauge surged at 18:15 CST March 7 (independently confirmed — independent local rain in Bear Creek watershed). - The Harriet acceleration at ~06:30 CDT March 8 (shortly after St. Joe began receding from its peak) is clearly mainstem propagation from St. Joe.
Signal separation for Harriet — Bear Creek gauge check: - Bear Creek is in recession all day March 8 (48.6 → 33.5 cfs). No new inputs. - Therefore, the massive Harriet surge (315 → 3,050 cfs) is overwhelmingly mainstem propagation from upstream, not independent Bear Creek contribution. Bear Creek is providing only ~33-49 cfs of the total. - This is a textbook signal separation result — Bear Creek flat/falling while Harriet surges = mainstem propagation confirmed.
Event 2 — Complete propagation timing now available:
| Gauge | Peak Time | Lag from Ponca Peak | Lag from Pruitt Peak |
|---|---|---|---|
| Ponca | 3/07 07:30 CST | 0 hr | — |
| Pruitt | 3/07 13:15 CST | 5.75 hr | 0 hr |
| St. Joe | 3/08 ~03:30 CST | 20 hr | 14.25 hr |
| Harriet | 3/08 ~11:30 CDT (~10:30 CST) | 27 hr | 21.25 hr |
Reach velocities at flood flow (Event 2): | Reach | Distance (est.) | Time | Velocity | |-------|----------------|------|----------| | Ponca → Pruitt | ~25 km | 5.75 hr | ~1.2 m/s | | Pruitt → St. Joe | ~50 km | 14.25 hr | ~0.97 m/s | | St. Joe → Harriet | ~30 km | 7.0 hr | ~1.2 m/s | | Ponca → Harriet | ~105 km | 27 hr | ~1.08 m/s |
Key observation: The Pruitt → St. Joe velocity (~0.97 m/s) is SLOWER than both the Ponca→Pruitt and St. Joe→Harriet reaches. This is notable because St. Joe's flow was INCREASING during transit (receiving tributary inputs from the 1,342 km² zone), so the pulse was being RESHAPED, not just translated. The flood wave at St. Joe is a composite of the upstream pulse + local tributary inputs arriving over ~24 hours, which broadens and delays the apparent peak.
Attenuation analysis: - Ponca peaked at 2,120 cfs (390 km² watershed). - Pruitt peaked at 2,610 cfs (513 km², 23% more area — peak grew by 23%). - St. Joe peaked at 3,230 cfs (1,932 km², 277% more area — peak grew only 52% despite nearly tripling the area). Significant attenuation. - Harriet peaked at 3,050 cfs (2,775 km², 44% more area than St. Joe — peak DECREASED by 6%). The wave is attenuating faster than new tributaries are adding flow.
This attenuation pattern makes physical sense: the 1-2" of rain in the lower HUC12s produces distributed, gradual inputs that raise the base but don't sustain the sharp peak.
Event 2 is now a 3-day event (March 7-8-9 probable):
Complete Event 2 magnitude summary:
| Gauge | Pre-Event | Peak | Rise | Peak Time | Current (3/08 EOD) |
|---|---|---|---|---|---|
| Boxley | 2.47 ft | 3.28 ft | +0.81 ft | 3/07 16:15 CST | 2.88 ft (receding) |
| Ponca | 145 cfs | 2,120 cfs | +1,975 cfs (+1,362%) | 3/07 07:30 CST | 277 cfs |
| Pruitt | 4.04 ft / 174 cfs | 8.55 ft / 2,610 cfs | +4.51 ft / +2,436 cfs | 3/07 13:15 CST | 5.21 ft / 556 cfs |
| St. Joe | 3.41 ft / 153 cfs | 8.01 ft / 3,230 cfs | +4.60 ft / +3,077 cfs | 3/08 ~03:30 CST | 6.58 ft / 1,860 cfs |
| Harriet | 3.53 ft / 172 cfs | 6.83 ft / 3,050 cfs | +3.30 ft / +2,878 cfs | 3/08 ~11:30 CDT | 6.26 ft / 2,390 cfs |
| Richland | 1.16 ft | 2.55 ft | +1.39 ft | 3/07 ~16:15 CDT | 2.05 ft |
| Bear Creek | 2.32 ft / 6.58 cfs | 2.91 ft / 48.6 cfs | +0.59 ft / +42 cfs | 3/07 ~21:30 CST | 2.76 ft / 33.5 cfs |
All mainstem gauges remain in Optimal range. St. Joe and Harriet will likely remain elevated well into March 9. Ponca may drop below Optimal (200 cfs) by late March 9.
Harriet peak exceeded St. Joe peak by approach but not by magnitude — and this is informative. The Harriet peak (3,050 cfs) was slightly BELOW the St. Joe peak (3,230 cfs), despite Harriet draining 843 km² more watershed. This means: 1. The flood wave attenuates significantly between St. Joe and Harriet (30+ km of channel storage). 2. The Harriet-zone tributaries (430 km²) and Bear Creek (239 km²) produced only modest direct runoff (~1" over these areas), insufficient to offset channel attenuation. 3. This is the first empirical constraint on the St. Joe → Harriet attenuation ratio: approximately 0.94x at these flow levels (~3,000 cfs). For forecasting purposes, the St. Joe peak is approximately equal to the Harriet peak with a ~7 hour delay.
Boxley recession extremely slow — 0.01 ft/hr. The pool-and-drop system that delays the rising limb also delays recession, acting as distributed storage. Boxley is still at 2.88 ft, nearly 1 ft above baseflow, 48+ hours after rainfall ended. This is consistent with local knowledge about pool dynamics — the pools are now slowly draining.
The Pruitt-Ponca relationship at high flow is firmly resolved. At the Event 2 peak, Pruitt exceeded Ponca by 490 cfs (2,610 vs 2,120). During recession today, Pruitt (556 cfs) still exceeds Ponca (277 cfs) by 2x. The low-flow inversion is definitively a low-flow phenomenon.