Last updated: April 26, 2026 at 11:59 PM

Updated Hypothesis Document

Buffalo River Watershed — Running Hypothesis Document

Last updated: 2026-04-26 (Day 57) Events observed to date: 7 confirmed rainfall-runoff events + 1 sub-threshold pulse + 1 sub-threshold non-detection - Event 1: March 5-6, 2026 — moderate upper watershed storm (Tier 2) — COMPLETE - Event 2: March 7-8, 2026 — major widespread storm (Tier 3, High Water) — COMPLETE - Event 3: March 11-12, 2026 — moderate upper watershed storm (Tier 2) — COMPLETE - March 15 pulse: Sub-threshold/marginal — 0.4-0.5" on dry antecedent - March 27 rain: Sub-threshold/non-detection — 0.1-0.4" on extreme dry antecedent - Event 4: April 2-5, 2026 — Compound three-pulse event, Tier 2 — COMPLETE - Event 5: April 10-11, 2026 — Two-zone minor event. Tier 1 — COMPLETE - Event 6: April 15-20, 2026 — Multi-pulse moderate widespread event. Tier 1-2 — COMPLETE - Event 7: April 24-26, 2026 — Watershed-wide event. Tier 2 (Recreational) — COMPLETE

Study Context

This is the hypothesis document for a 90-day empirical study (March–June 2026) correlating MRMS radar-estimated precipitation with USGS gauge responses across the Buffalo River watershed (HUC8 11010005, 3,471 km²). Seven active gauges monitor five mainstem points and two tributaries. The watershed is divided into 37 HUC12 sub-watersheds, 29 of which drain to gauged locations (79.9% of total area).

EVENT LOG

Event 1: March 5-6, 2026 — Upper Watershed Storm

Classification: Tier 2 (Recreational response) — CONFIRMED
Boxley +0.87 ft; Ponca +95 cfs; Pruitt +0.71 ft / +144 cfs; Richland +0.26 ft; Harriet +0.04 ft
Propagation: Boxley → Ponca (4-5 hr) → Pruitt (20 hr from Boxley peak)

Event 2: March 7-8, 2026 — Major Widespread Storm

Classification: Tier 3 (High Water) — CONFIRMED
Peak responses: Ponca 2,120 cfs; Pruitt 8.55 ft / 2,610 cfs; St. Joe 8.01 ft / 3,230 cfs; Harriet 6.83 ft / 3,050 cfs

Event 3: March 11-12, 2026 — Moderate Upper Watershed Storm

Tier 2 confirmed at all gauges. Stacked event on very wet antecedent.

Event 4: April 2-5, 2026 — Compound Three-Pulse Event

Tier 2 overall; Pruitt approached Tier 3 briefly
Lag times (QPE centroid → gauge peak): Boxley 11h, Ponca 13h, Pruitt 21h, St. Joe 33.5h, Harriet 40.25h

Event 5: April 10-11, 2026 — Two-Zone Minor Event — Tier 1

Event 6: April 15-20, 2026 — Multi-Pulse Moderate Widespread Event — Tier 1-2

Event 7: April 24-26, 2026 — Watershed-Wide Event (COMPLETE)

Classification: Tier 2 (Recreational) — CONFIRMED
Precipitation: Apr 24 watershed-wide 0.9-1.6"; light Apr 25 tail (0.08-0.42"). Peak HUC12s: Water Cr 1.486", Tomahawk 1.374", Boxley 1.249", Pruitt zone 1.35", Cove Cr 1.343", Hoskin 1.362". Bear Creek zone 0.90-0.99".
Antecedent: Dry — 0.30-0.72" 7-day at onset.
Final peak gauge response summary:

Gauge	Pre	Peak	Rise	Peak Time	Lag from QPE centroid
Boxley	2.19 ft	3.21 ft	+1.02 ft	04/24 16:30	~10.5 hr
Ponca	115 cfs	347 cfs	+232 cfs	04/24 18:15	~12.25 hr
Pruitt	119 cfs / 3.77 ft	612 cfs / 5.31 ft	+493 cfs / +1.54 ft	04/25 03:00	~21 hr
St. Joe	295 cfs / 3.84 ft	1,460 cfs / 5.99 ft	+1,165 cfs / +2.15 ft	04/25 17:15	~35 hr
Harriet	385 cfs / 3.97 ft	1,610 cfs / 5.52 ft	+1,225 cfs / +1.55 ft	04/26 02:00	~40 hr
Richland	1.32 ft	2.50 ft	+1.18 ft	04/24 17:15	~11 hr
Bear Creek	17.5 cfs / 2.17 ft	37.1 cfs / 2.44 ft	+19.6 cfs / +0.27 ft	04/25 13:30	~26 hr

Event 7 propagation chain (FINAL): Boxley→Pruitt 10.5h, Pruitt→St.Joe 14.25h, St.Joe→Harriet 8.75h. Total Boxley→Harriet: ~33.5h. Closely matches Event 4.
Recreational status: Pruitt, St. Joe, Harriet in Optimal entire event. Boxley brief Low-Floatable (~3 hours @ 3.2 ft on Apr 24). Richland did NOT reach 3.2 ft (peaked 2.50 ft).

RECESSION BEHAVIOR OBSERVATIONS

Two-phase recession pattern fully confirmed. 1. Propagation waves can mask recession at downstream gauges for 1-2 days after rain ceases. 2. Fast interflow recession (1-3 days) → slower groundwater baseflow recession (3+ days). 3. Larger drainage areas → slower percentage recession. 4. Pre-Event 7 baseline (Apr 24 00:00): Boxley 2.19 ft, Ponca 115 cfs, Pruitt 119 cfs, St. Joe 295 cfs, Harriet 385 cfs — useful "near-baseflow after 6 dry days" reference. 5. Post-Event 7 recession rates (Day 57 observations): St. Joe declining ~330 cfs/day from 1,330 cfs; Harriet declining ~350 cfs/day from 1,610 cfs. These are early-recession rates (high-volume interflow phase).

RATING CURVE OBSERVATIONS

Bear Creek Rating Curve Shift (Apr 14, 2026)

Apr 14 ~15:30: discharge jumped from ~3.4→21 cfs at unchanged 2.23 ft. Pre-Apr 14 CFS: low confidence.

Bear Creek Behavior

Refined Bear Creek hypothesis (Day 57): - Activation threshold: ~0.9-1.0" QPE on moderate antecedent (>0.4" 7-day) produces a measurable response. - Dry antecedent activation threshold: Possibly higher (no clear data point yet). - Sub-threshold confirmation Day 57: 0.20" QPE on wet antecedent (1.0+ 7-day) produced no detectable rise. Confirms activation threshold is real and well above 0.2", even when ground is wet. - Transfer ratio (dry-moderate antecedent): ~0.27 ft/in, ~18-20 cfs/in. - Lag time: ~26 hr from QPE centroid to peak — substantially longer than other gauges of similar size. - Damping: ~3-5× lower transfer ratios than Pruitt or Richland.

CROSS-EVENT FINDINGS (updated Day 57)

Antecedent moisture amplification: Wet antecedent (>1" 7-day) roughly 1.5-2× transfer ratio vs. dry antecedent (<0.7" 7-day).
Boxley "pool and drop": Modest in magnitude. Day 57 small post-event response (0.18" → ~0.08 ft net) on wet antecedent gives ~0.4-0.5 ft/in, consistent with wet-antecedent amplification.
Propagation lag stability: Events 4 and 7 show nearly identical propagation lags (Pruitt 21h both; St. Joe 33.5h vs 35h; Harriet 40h vs 40h) despite different antecedent conditions. Lag time depends primarily on flow magnitude, not antecedent moisture. Antecedent affects amplitude, not timing. CONFIRMED with Event 7 final data.
Pruitt-Tier-3 boundary: Estimated threshold ~2"+ on watershed with at least moderate antecedent. Event 7 at 1.35" only reached Pruitt 612 cfs.
Local knowledge calibration — Upper Richland: 2 of 7 events have produced upper Richland Low-Floatable conditions (Events 2 and 4). Event 7's 2.50 ft peak (1.05" zone QPE on dry antecedent) fell short of 3.2 ft threshold. Confirms local "3-7 runs/year" guidance.
Bear Creek karst hypothesis confirmed: Bear Creek does respond, but at ~3-5× lower transfer ratio than other gauges. "Strongly damped response with elevated activation threshold (~0.9-1.0")."
Tributary detection thresholds (NEW Day 57): Day 57 Richland zone 0.27" QPE on wet antecedent produced only ~0.05 ft visible rise (mostly masked by recession). Suggests Richland gauge detection threshold for clear signatures is approximately 0.4-0.5" QPE, even with wet antecedent. Below that, response is buried in recession noise.
Harriet peak prediction validated (NEW Day 57): Day 56 hypothesis predicted Harriet peak "overnight Apr 25/26" — actual peak was 04/26 02:00. The ~40 hr Boxley→Harriet propagation lag is a reliable forecasting tool for moderate-magnitude events.

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