Today (Day 33, April 2) marks the first measurable rainfall across the watershed since the March 27 trace event — and the first meaningful precipitation in 22 days since Event 3 ended on March 12.
Spatial pattern: Rain was concentrated in the upper-to-middle watershed with a strong NW-to-SE gradient:
| Zone | 24hr Total | Peak 1hr | Peak HUC12 | Notes |
|---|---|---|---|---|
| Boxley | 0.517" | 0.185"/hr | Terrapin Branch 0.517" | Highest zone total |
| Ponca | 0.332" | 0.143"/hr | Smith Creek 0.422" | Moderate |
| Pruitt | 0.161" | 0.082"/hr | Hoskin Creek 0.181" | Light |
| St. Joe | 0.259" | 0.213"/hr | Cave Creek 0.340" | Variable — some HUC12s got 0.32-0.34", others 0.14" |
| Richland | 0.290" | 0.252"/hr | Headwaters RC 0.414" | Moderate, highest intensity in watershed |
| Bear Creek | 0.101" | 0.044"/hr | Headwaters BC 0.129" | Very light |
| Harriet | 0.105" | 0.093"/hr | Tomahawk 0.185" | Light |
| Ungauged | 0.037" | 0.055"/hr | Clabber Creek 0.089" | Negligible |
Timing: Rain fell primarily between 14:02-17:02 UTC (9 AM - noon CDT), concentrated in a ~3-6 hour window. Low intensity throughout — peak 1hr rates were 0.10-0.25"/hr, well below convective thresholds.
Key HUC12s with >0.3": Boxley (0.517"), Headwaters Richland (0.414"), Smith Creek (0.422"), Headwaters LB (0.380"), Beech Creek (0.352"), Headwaters Big Creek (0.343"), Cave Creek (0.340"), Left Fork Big Creek (0.321").
Boxley (07055646): Marginal but real rise detected. Height went from 1.76 ft (study low, new record at 03:45-05:30 CST) to 1.81 ft by end of day. Rise of +0.05 ft. The rise began ~09:30 CST (gap in data from 07:30-09:30, but 1.78 at 09:30 vs 1.76-1.77 before) and continued gradually through the day. This is the first positive movement at Boxley in weeks. At 1.81 ft, Boxley is back to levels last seen on March 30-31. This is notable because Boxley received the highest zone rainfall (0.517") and is responding, albeit weakly, on extremely dry antecedent conditions (22 days since meaningful rain).
Ponca (07055660): No meaningful response. Discharge remained pinned at 82.4-85.1 cfs (same range as Days 31-32). A few readings hit 85.1 in the afternoon, but this is within normal noise. Ponca zone received 0.332" average — below detection threshold for extreme dry conditions.
Pruitt (07055680): No response. Height 3.41-3.46 ft, discharge 43.0-49.5 cfs — consistent with prior days and continuing the slow baseflow decline. The 43.0 cfs reading at 15:15 is a new study low for Pruitt discharge. Pruitt zone received only 0.161" — far below any detection threshold.
St. Joe (07056000): No clear response above noise. Height 3.39-3.45 ft, CFS 156-175. The late-day readings (20:00-23:00) showed a slight firming at 3.42-3.45 ft and 165-175 cfs, which may represent the earliest hint of a response, but this is within the noise floor of recent days. St. Joe zone received 0.259" average — below extreme-dry detection threshold.
Harriet (07056700): Continued slow decline. Height dropped from 3.55 to 3.53 ft, discharge from 180 to 172 cfs — new study lows. Harriet zone received only 0.105" — no response expected or detected.
Richland Creek (07055875): Clear rise detected. Height went from 0.89 ft (baseline) to 0.98 ft peak by ~16:15 CST, a rise of +0.09 ft. This is the most unambiguous signal in today's data. The rise began ~10:00 CST (0.92 ft, up from 0.89 at 08:15), reached 0.93 by 10:30, 0.95 by 14:00, 0.96 by 14:45, 0.97 by 15:30, and peaked at 0.98 by 16:15. By end of day the gauge was holding at 0.97. Richland zone received 0.290" average, with Headwaters Richland Creek getting 0.414" at 0.252"/hr peak intensity.
Bear Creek (07056515): No response. Height 2.27-2.29, discharge 4.19-5.03 cfs — all within noise. Bear Creek received only 0.101" — consistent with 5th non-detection at this gauge below 0.6".
Pair 1: Boxley headwaters rainfall → Boxley gauge - Rain: 0.517" over ~6 hours, peak 0.185"/hr - Response: +0.05 ft (1.76→1.81), beginning ~3-4 hours after rain onset - Antecedent: Extreme dry — 0.10" 7-day (essentially trace), 22 days since meaningful rain - Transfer ratio: 0.517" → 0.05 ft rise = 0.097 ft/inch - Comparison to hypothesis: The current dry-antecedent detection threshold for Boxley was estimated at ≥0.8". Today shows that 0.52" produced a detectable +0.05 ft response, suggesting the extreme-dry threshold should be revised downward, perhaps to ~0.5". However, this is a very small response — at the edge of detection. The local knowledge about pools needing to "fill" before water reaches Boxley is relevant: the 0.05 ft rise may represent only partial pool-filling, not true runoff reaching the gauge. The gradual, sustained nature of the rise (over ~12 hours) is consistent with slow seepage rather than surface runoff.
Pair 2: Richland Creek headwaters rainfall → Richland gauge - Rain: 0.414" at Headwaters RC (HUC12 0306), 0.166" at Falling Water Creek (0307); zone average 0.290" - Response: +0.09 ft (0.89→0.98), gradual rise beginning ~10:00 CST (rain peaked at 15:02 UTC = 10:02 CDT, so nearly simultaneous onset) - Antecedent: Extreme dry — 0.14-0.15" 7-day, 22 days since meaningful rain - Transfer ratio: 0.290" zone average → 0.09 ft rise = 0.31 ft/inch (zone avg) or 0.414" peak HUC12 → 0.09 ft = 0.22 ft/inch - Comparison to hypothesis: Previous data showed 0.57" → 0.08 ft (marginal) on wet antecedent (Event 3), and 0.30" → nothing on dry antecedent (Day 15). Today's 0.29" zone average (0.41" in headwaters) → 0.09 ft on extreme dry conditions is surprising — more response than expected given the drought. However, this may reflect karst spring behavior at Richland rather than simple infiltration-excess runoff: the Headwaters RC HUC12 received 0.414" at 0.252"/hr, the highest intensity in the watershed today. In karst terrain, even modest rain can produce quick spring pulses through preferential flow paths. The +0.09 ft is still below the noise threshold I previously estimated (±0.05 ft for karst spikes), but the sustained, progressive nature of this rise (not a spike-and-drop) confirms it's real hydrological response.
This Richland observation challenges the previous detection threshold of >0.6" zone average. The key may be the peak HUC12 intensity (0.252"/hr on the headwaters unit, which is 65% of the zone area). I'll need to revise the Richland threshold to account for spatial concentration.
No downstream propagation to track. The Boxley response is too small to produce a detectable wave at Ponca, and no upstream mainstem rises were observed.
This is a single-day event. No prior-day rainfall to extend. Tomorrow will be important to track whether: 1. Boxley continues rising (would suggest slow pool-filling continuing) 2. Richland peak propagates to St. Joe (would provide another signal-separation data point) 3. Ponca shows any delayed response from the Boxley-zone rain
Surprise 1 — Richland responded more than expected. At 0.29" zone average on extreme dry antecedent, the +0.09 ft rise contradicts my previous estimate that >0.6" was needed. Possible explanations: (a) the 0.414" on the headwaters unit (which is 113 km² of the 174 km² zone = 65% of area) is the relevant driver, not the zone average; (b) karst conduits in the Richland basin may have shorter residence times than surface/soil pathways, allowing faster response even on dry soils; (c) the Richland gauge may be more sensitive to small inputs than I estimated.
Surprise 2 — Boxley responded at 0.52" on extreme dry. The previous threshold estimate was ≥0.8". This needs downward revision, though the response is marginal (0.05 ft).
Surprise 3 — Ponca did NOT respond despite receiving 0.33" zone average. This is consistent with the extreme-dry threshold hypothesis (≥0.5-0.6"), but creates an interesting contrast with Boxley (which did respond to 0.52"). The Boxley headwater HUC12 is a single 92 km² unit that got concentrated rain, while Ponca's 3 HUC12s received variable amounts (Beech 0.35", Smith 0.42", Whiteley 0.22"). The aggregation across a larger area may dilute the effective input.
Local knowledge comparison: The "pool and drop" observation for upper Buffalo above Boxley is directly relevant. Today's 0.52" on extreme dry produced only a 0.05 ft rise — consistent with rain "filling pools" rather than producing runoff. The slow, gradual rise (12+ hours) matches this mechanism.
New baseflow lows observed: - Boxley: 1.76 ft (new study low, down from 1.77) - Pruitt: 43.0 cfs (new study low, down from 45.5) - Harriet: 168 cfs (new study low via single reading at 15:15, but sustained 172 cfs by evening)