Essentially a dry day across the watershed. Today's QPE is negligible: - Boxley zone: 0.065" (peak 0.064"/hr at ~17:02 CST — a single brief cell) - Ponca zone: 0.035" average - Pruitt zone: 0.012" - St. Joe zone: 0.027" average (Left Fork Big Creek had 0.109" — highest individual HUC12) - Richland: 0.001" - Bear Creek: 0.000" - Harriet: 0.000"
No rainfall today exceeds the detection threshold at any gauge. This is functionally a dry day for runoff analysis purposes.
Two notable features today: (A) delayed Boxley response from yesterday's late-evening Boxley-zone rain, and (B) a delayed Pruitt rise from upstream propagation.
Boxley: Clear response visible. Rose from 2.39 ft at 23:15 CST on Apr 10 to peak 2.59 ft at ~01:30-02:15 CST on Apr 11, a rise of +0.20 ft in ~2 hours. This is a clean, well-defined pulse. Recession followed smoothly, returning to 2.39 ft by ~23:00 CST Apr 11. Total excursion duration: ~22 hours.
Ponca: Response to the Boxley pulse visible. Ponca was at 143 cfs at 00:00 CST and rose to 163 cfs by ~06:45 CST (+20 cfs, +14%). This is a modest but clear propagation of the Boxley pulse. Recession then resumed, ending the day at 145 cfs. Ponca remains below the Too Low threshold (<150 cfs) for much of the day but briefly re-entered Low-but-Floatable (150-200 cfs) from ~01:15 to ~15:00 CST.
Pruitt: Shows a distinct rise starting ~16:30-17:00 CST, from a low of 4.03 ft / 185 cfs to a peak of ~4.15 ft / 219 cfs at ~21:00 CST (+0.12 ft / +34 cfs). This is not from today's negligible local rainfall. This is the propagation of the Boxley pulse arriving at Pruitt. The timing works: Boxley peaked at ~01:30 CST Apr 11, Pruitt rise begins ~16:30 CST = ~15 hours lag from Boxley peak. This is consistent with previous Boxley→Pruitt propagation times (20 hr in Event 1 at lower flow, 10 hr in Event 4 at higher flow). At the intermediate flow conditions today (~185 cfs), 15 hours is a reasonable intermediate value. Pruitt re-crossed back above 200 cfs (Optimal threshold) at ~17:30 CST, ending the day at 211 cfs.
Important recession note: There's also likely a contribution from Cove Creek's 0.657" rainfall yesterday evening (Apr 10, peak at ~16:02 CST). That rainfall, entering Pruitt's direct drainage, may be partially responsible for this rise. The combined effect of upstream propagation from Boxley AND direct Cove Creek input likely explains the Pruitt rise.
St. Joe: Continued smooth recession all day. 504 cfs → 433 cfs (EOD). Daily decline of ~14.5% — recession is decelerating further (was ~16.5%/day two days ago). No detectable response to the upstream pulse yet — expect it to arrive in 12-24 hours. Height fell from 4.40 to 4.23 ft. Still well within Optimal range (>200 cfs).
Harriet: Continued recession from yesterday's brief rain-boosted level. 756 cfs (SOD) → 608 cfs (EOD). Daily decline of ~19.7%. Height fell from 4.54 to 4.31 ft. The Event 5 rain bump has now fully receded through. Still well within Optimal range (>200 cfs).
Richland Creek: 1.57 → 1.48 ft. Steady recession, no response. This is now approaching the lowest levels we've seen in the study.
Bear Creek: 2.33 → 2.29 ft, 7.19 → 5.03 cfs. Steady recession, approaching pre-Event 4 baseflow levels (~4.2 cfs).
Boxley response to Apr 10 evening rain (Event 5 continuation): - Rainfall: Boxley zone received 0.553" on Apr 10, peak intensity 0.297"/hr at ~18:02 CST (23:02 UTC). Most rain fell in a 3-hour window (0.549"). - Response: +0.20 ft rise at Boxley, starting ~23:15 CST Apr 10, peaking ~01:30 CST Apr 11. - Lag time: QPE peak at ~18:02 CST → gauge rise onset at ~23:15 CST = ~5 hours. QPE peak → gauge peak at ~01:30 CST = ~7.5 hours. - Transfer ratio: 0.553" → +0.20 ft = 0.36 ft per inch. - Antecedent: Moderate — 7-day precip ~2.1" in Boxley zone, gauges still elevated from Event 4 recession. - Comparison to prior data: In Event 1, 1.038" produced +0.87 ft (0.84 ft/inch); in Event 3, 0.811" produced +0.66 ft (0.81 ft/inch); in Event 4, 1.57" produced +2.05 ft (1.31 ft/inch on very wet antecedent). Today's 0.36 ft/inch is notably lower. Possible explanations: (1) the rain fell late evening with lower intensity than those events, (2) the watershed, while moist (~2.1" 7-day), may be less saturated than during Events 3-4, (3) the pool-and-drop nature of the upper Boxley reach (per local knowledge) may absorb more at moderate rain amounts. This data point suggests a non-linear response: at lower rainfall intensities/totals (~0.5"), the ft/inch ratio is lower than at higher amounts (~1.0"+), supporting a threshold-type response consistent with the karst/pool-and-drop geology. - Confidence: High — clean isolated event, clear QPE-response pair.
Pruitt response — compound source: - Two inputs likely contribute to the Pruitt rise: (1) Upstream propagation of Boxley pulse; (2) Cove Creek 0.657" (peak 0.507"/hr) from yesterday evening. - Cannot cleanly separate the two contributions. The timing of the rise onset (~16:30 CST) is consistent with both: Boxley peak at 01:30 → 15 hr propagation to Pruitt; Cove Creek QPE peak at ~16:02 CST Apr 10 → 24 hr lag to Pruitt. Both could contribute. - Net rise at Pruitt: +0.12 ft / +34 cfs. Modest but enough to push Pruitt back above Optimal briefly.
Boxley pulse propagation (Apr 10 evening rain): - Boxley peak: ~01:30 CST Apr 11 - Ponca peak: ~06:45 CST Apr 11 → +5.25 hours from Boxley - Pruitt rise onset: ~16:30 CST Apr 11 → ~15 hours from Boxley peak (note: confounded with Cove Creek input) - Pruitt peak: ~21:00 CST Apr 11 → ~19.5 hours from Boxley peak
These propagation times are faster than Event 1 (Boxley→Ponca was 4-5 hr, Boxley→Pruitt was 20 hr) but consistent with slightly elevated baseflow. The Boxley→Ponca time of 5.25 hours is at the upper end of previous observations.
Expected at St. Joe: The Pruitt pulse (peak ~21:00 CST Apr 11) should produce a small, detectable bump at St. Joe within 12-24 hours (i.e., by Apr 12 afternoon/evening). Given the small magnitude (+34 cfs at Pruitt on a declining baseflow of ~185 cfs), it may be barely detectable at St. Joe against the background recession noise.
Event 5 is now better characterized as a two-zone event: - Harriet zone (Apr 10): 0.6-1.1" → +0.10 ft / +73 cfs at Harriet. Now fully receded. - Boxley zone (Apr 10 evening/Apr 11): 0.553" → +0.20 ft at Boxley, propagating downstream through Ponca (+20 cfs) and Pruitt (+34 cfs, with Cove Creek contribution). - Cove Creek / Pruitt zone (Apr 10): 0.657" → contributing to Pruitt rise on Apr 11.
Event 4 recession status (Day 9 since peak, Day 8 of post-event): - Ponca: 145 cfs at EOD — in "Too Low" range (<150), though briefly re-entered floatable today from upstream pulse. - Pruitt: 211 cfs at EOD — back in Optimal (>200) thanks to upstream pulse + Cove Creek input. This is temporary; will likely decline again. - St. Joe: 433 cfs at EOD — still solidly in Optimal. At current recession rate (~14.5%/day, decelerating), projected to remain above 200 cfs through ~Apr 17-18. - Harriet: 608 cfs at EOD — still solidly in Optimal. Should remain above 200 cfs through ~Apr 18-20.
Non-linear Boxley response ratio: The 0.36 ft/inch transfer ratio at Boxley for 0.553" input is substantially lower than the 0.81-1.31 ft/inch seen in previous events with 0.8-1.6" inputs. This supports a hypothesis of non-linear response — the first ~0.3-0.5" of rainfall on moderately moist ground produces less gauge response per inch than amounts above that threshold. This is consistent with the local knowledge about pool-and-drop terrain needing to "fill pools" before water transmits efficiently. Even on wet antecedent, below ~0.5" total rainfall, the response efficiency appears to drop significantly.
Event 5 Harriet response already gone: The +73 cfs Harriet bump from 0.6-1.1" of rain lasted less than 24 hours. This fast recession of the local response confirms that Harriet's direct tributaries (430 km² of local drainage) respond quickly but don't sustain flow — the sustained baseflow at Harriet comes overwhelmingly from upstream propagation through the 2,345 km² above.