Daily Analysis

Day 66 — May 5, 2026. The forcing event we needed has arrived. A morning rainfall pulse on the now-dry watershed delivered the cleanest dry-antecedent calibration data of the study, and Boxley produced its first observed Optimal-Hailstone-class rise.

1. PRECIPITATION SUMMARY

Strong morning convective pulse, peak hour ~09-10 CDT (14-15 UTC), focused on the western/southern watershed. Spatial pattern clearly favors upper Buffalo headwaters + Richland headwaters / Big Cr / Cave Cr + Bear Cr headwaters:

Zone	24-hr QPE	Peak 1-hr	Max 6-hr	Notes
Boxley	1.23"	0.53"	1.10"	Terrapin Branch HUC 0201
Ponca	0.76"	0.59"	0.84"	Whiteley Cr 0205 strongest
Pruitt	0.45"	0.28"	0.48"	Light
St. Joe	0.72" zone-avg	0.76"	1.11"	Non-uniform: Shop Cr 0101 1.17", Big Cr HW 0302 1.06", Outlet Richland 0308 1.10"
Richland	1.04"	0.62"	0.77"	HW Richland 0306 1.15"
Bear Cr	0.92"	0.78"	0.98"	HW Bear 0403 1.23"
Harriet	0.27"	0.12"	0.25"	Marginal

Hotspots (>1.0" / 24 hr): Shop Cr (1.17), Hdwtrs LB (1.02), HW Big Cr (1.06), HW Richland (1.15), Outlet Richland (1.10), Headwaters Bear (1.23), Terrapin/Boxley (1.17), Boxley zone (1.23). Storm track: WSW→ENE morning convection.

2. GAUGE RESPONSES

Boxley — 🟢 First Optimal Hailstone observation of study. Pre-rise 2.29 ft @ 03:45 → peak 3.16 ft @ 12:15. Rise +0.87 ft total, +0.53 ft in the hour ending 10:30. Boxley crossed Hailstone Low-but-Floatable (3.2 ft) momentarily — peaked just at/below 3.2 ft. Already on recession by 12:30, dropping to 2.77 ft by 23:30 (-0.39 ft / 11 hr).

Ponca — Pre-rise 206 cfs @ ~03 CDT → peak 396 cfs @ 15:15-16:00. Rise +190 cfs (+92%). Below Low-Floatable threshold (still in Optimal CFS class, well above 200).

Pruitt — Slow steady rise from 4.02 ft / 183 cfs (overnight) to 4.22 ft / 238 cfs by 23:30, still rising at end-of-day. Rise +0.20 ft / +55 cfs and not peaked. Initial Pruitt-zone QPE was light (0.45"), so this is upstream propagation arriving.

Richland Cr — Pre-rise 1.53 ft → peak 1.79 ft @ 13:45-14:00. Rise +0.26 ft. Sharp jump from 1.56→1.64 in 15 min at 04:45-05:00 CDT (note this leads the QPE peak — likely flashy headwaters response). Already receding by mid-afternoon. Stayed well below Tier-2 thresholds.

Bear Creek — Pre-rise 2.34 ft / 28.5 cfs → peak 2.66 ft / 62.8 cfs @ 19:15. Rise +0.32 ft / +34 cfs. Lag from 10 CDT peak rainfall to peak gauge ≈ 9 hr — much shorter than the 26 hr lag observed in Event 8 wet conditions. Notable.

St. Joe — Essentially flat. Drifting down from 4.41 ft / 530 cfs through 4.30-4.33 / 482-499 cfs through the day. No discernible response yet — propagation still in transit (Pruitt only began rising late evening). Watch tomorrow.

Harriet — Same pattern, pure recession. 4.48 → 4.37 ft, 712 → 635 cfs.

3. RAINFALL-RESPONSE PAIRS — CLEAN DRY-ANTECEDENT DATA

This is the highest-value forcing event of the study for transfer-function calibration. Antecedent: 1.4 wet → fully decayed by Day 66 (7-day antecedent now 0.7-1.4" but distributed across many days; soils approached dry baseline as confirmed Day 65).

Boxley (Hailstone, dry-antecedent): - QPE: 1.23" zone-avg, peak 1-hr 0.53" centered ~10 CDT (15 UTC). - Rainfall onset → Boxley first inflection: peak 1-hr at 09-10 CDT, Boxley begins clear rise ~04 CDT (slight pre-pulse from edge cell?), main rise 09:30-12:15. Lag from peak rainfall to peak gauge ≈ 2-2.5 hr. Much faster than Event 8 (5-6 hr wet). Why faster? Larger rain rate (0.5"/hr) → overland flow dominated, bypassing pool-fill mechanism. - Transfer ratio: +0.87 ft / 1.23" = 0.71 ft/inch zone-avg. Compares to: - Wet-antecedent Boxley: ~1.0-1.1 ft/in - Dry-antecedent Boxley (prior): 0.4-0.5 ft/in - Today's value (0.71 ft/in) sits between — consistent with "moderate dry, but high-intensity burst overcame pool storage faster than typical dry events." - Local knowledge calibration: Hailstone at 3.2 ft = Low-but-Floatable threshold for the Boxley→Ponca section (per local notes). Boxley peaked at 3.16, just below. The Hailstone proper threshold (3.7 ft Low-Float) was NOT reached. Threshold confirmation: ~1.5"+ zone-avg dry would likely reach Hailstone Low-Float.

Ponca: - Boxley peak 12:15, Ponca peak ~15:15. Boxley→Ponca lag ≈ 3 hr (vs 2.25 hr wet — slightly slower with dry channel). - Discharge rise 190 cfs on Ponca-zone 0.76" + Boxley contribution. Hard to clean-decompose.

Pruitt: - Active rise still in progress at end-of-day. Ponca peak ~15:15 → Pruitt at 4.22 / still rising 23:30. Ponca→Pruitt lag at least 8 hr and ongoing — consistent with prior 7.5 hr wet estimate.

Bear Creek (dry-antecedent — KEY DATA): - QPE: 0.92" zone-avg, HW Bear 0403 = 1.23", peak 1-hr 0.78" @ ~10 CDT. - Rise +0.32 ft / +34 cfs, peak at 19:15 CDT. - Lag rainfall-peak → gauge-peak ≈ 9 hr. Dramatically shorter than Event 8 (~26 hr wet/saturated). - Transfer ratio: +0.32 ft / 0.92" = 0.35 ft/inch. Versus wet-antecedent 1.45 ft/in — ~4× lower under dry conditions. Critical finding. - REVISED HYPOTHESIS: Bear Creek's "extreme lag" finding from Event 8 was specific to saturated/wet conditions where karst conduits had pre-filled. On dry forcing with intense rainfall, response is much faster (~9 hr) AND much smaller (0.35 ft/in) — water absorbed by storage rather than channeling through karst.

Richland Creek (dry-antecedent): - QPE: 1.04" zone-avg, HW 0306 = 1.15", peak 0.62" @ 10 CDT. - Rise +0.26 ft, peak ~13:45. - Transfer ratio: 0.25 ft/inch zone-avg. Versus wet-antecedent observations of "near-1:1 ft/in" — again ~4× lower dry. - Lag rainfall peak → gauge peak ≈ 3.5-4 hr. Faster than wet-flash response too (interesting — in wet conditions Richland flashed in 60 min on rainfall maximum; here the slower rise reflects the transit through unsaturated soils and slower interflow buildup). - The 04:45-05:00 jump (1.56→1.64) preceded the QPE peak by 5 hr — likely an early-cell signature in Falling Water HW that arrived before the main convective burst.

4. DOWNSTREAM PROPAGATION

Cascade in progress: Boxley peak 12:15 → Ponca peak 15:15 (~3 hr) → Pruitt still rising at midnight (~12+ hr from Boxley). St. Joe and Harriet not yet responding (still in recession). Pulse expected to reach St. Joe early-mid Day 67, Harriet late Day 67-Day 68. Magnitude on dry watershed and modest QPE: probably +0.3-0.5 ft St. Joe, smaller at Harriet.

5. MULTI-DAY CONSIDERATIONS

This is the start of Event 9 — first new forcing since Event 8 (Apr 27-30). Watershed had 6 dry days of recession before this pulse. Total event magnitude depends on whether more rainfall follows. Today's pulse alone is sub-Tier-2 watershed-wide.

6. ANOMALIES / KEY FINDINGS

1. Bear Creek dry-vs-wet transfer ratio differs by ~4×. The Event 8 hypothesis ("extreme lag, not damping") needs nuancing: lag varies dramatically (9 hr dry vs 26 hr wet), and transfer also drops 4×. Implies karst conduit activation requires antecedent wetness to "prime" the system for rapid release.
2. Richland transfer dry ≈ 0.25 ft/inch, vs wet near-unity. Wet/dry amplification is also ~4× here.
3. Boxley dry-antecedent transfer 0.71 ft/in is intermediate — higher than typical dry-condition (0.4-0.5) due to high rainfall intensity. Suggests pool-fill model is rate-dependent: 0.5"/hr bursts overrun pool storage faster than 0.2"/hr drizzle.
4. Hailstone threshold confirmed: ~1.5" zone-avg dry-antecedent rainfall is the apparent floor for Hailstone Low-Floatable (3.7 ft); today's 1.23" produced 3.16 ft. Prior wet-condition estimate of "~1.7" zone-avg" is now bracketed.
5. No flag triggered for Bear Creek or Richland despite clear rises. The flagging logic only fired Boxley. Worth noting these gauges showed clean QPE→response signals.
6. St. Joe baseline behavior at 530 cfs / 4.41 ft today provides cleanest possible "true dry baseline" for the upcoming arrival of the pulse — Day 67 will refine St. Joe dry-condition transfer ratio for the first time this study.