1. PRECIPITATION SUMMARY: Zero precipitation recorded across all 37 HUC12s today. This is the second consecutive dry day (following the minor 0.16-0.48" pulse on Day 15). 7-day antecedent precip has risen slightly from yesterday due to the Day 15 pulse entering the rolling window — zone averages now range from 0.43" (Water Creek) to 1.29" (Beech Creek), with a watershed-wide average of approximately 0.75". This represents moderate antecedent conditions, transitioning toward dry.
2. GAUGE RESPONSES: All gauges are in uninterrupted recession. No significant rises detected at any gauge. Summary of current conditions vs. end-of-yesterday:
| Gauge | Start of Day | End of Day | Change | Rate | Recreational Status |
|---|---|---|---|---|---|
| Boxley | 2.55 ft | 2.41 ft | -0.14 ft | -0.006 ft/hr | Too Low |
| Ponca | 209 cfs | 171 cfs | -38 cfs (-18%) | -1.6 cfs/hr | Low but Floatable (150-200) |
| Pruitt | 4.46 ft / 293 cfs | 4.39 ft / 272 cfs | -0.07 ft / -21 cfs (-7%) | — | Optimal (>200) |
| St. Joe | 4.66 ft / 608 cfs | 4.63 ft / 594 cfs | -0.03 ft / -14 cfs (-2%) | — | Optimal (200-8000) |
| Harriet | 4.54 ft / 756 cfs | 4.42 ft / 670 cfs | -0.12 ft / -86 cfs (-11%) | — | Optimal (200-9370) |
| Richland | 1.45 ft | 1.38 ft | -0.07 ft | — | — |
| Bear Creek | 2.47 ft / 14.6 cfs | 2.45 ft / 13.7 cfs | -0.02 ft / -0.9 cfs | — | — |
Notable observations:
Ponca has crossed below the Optimal threshold (200 cfs) and is now in the "Low but Floatable" range (150-200 cfs). It crossed below 200 cfs around 16:00 CST and ended the day at 171 cfs. This is the first time Ponca has been below Optimal since March 6 (10 days of continuous Optimal/Flood conditions).
Pruitt remains in Optimal at 272 cfs but is trending toward the lower boundary. At the current recession rate (~1 cfs/hr), Pruitt could drop below Optimal (200 cfs) in approximately 3 days if no rain occurs.
Pruitt shows a notable bump in the early hours — height rose from ~4.46 ft at midnight to a local peak of ~4.54 ft around 06:00-08:30 CST before resuming recession. This is the arrival of the Day 15 rain pulse propagating from the Ponca zone. The Ponca pulse peaked around 15:45-16:45 CST on Day 15, and this bump arrives at Pruitt ~14-16 hours later, consistent with the low-flow propagation velocity (~0.46 m/s) observed in Event 1. This is a very clean propagation observation at low flow.
St. Joe shows considerable noise/oscillation in the height data today (range 4.56-4.70 ft), making trend analysis difficult. The CFS data is somewhat less noisy and shows a general decline from ~610 to ~590 cfs. The height oscillation (±0.05 ft on 15-minute intervals) may reflect turbulence, wind effects, or sensor noise at this flow level. This is worth monitoring.
Harriet recession is clean and steady — height declining from 4.54 to 4.42 ft over 24 hours (-0.12 ft).
3. RAINFALL-RESPONSE PAIRS:
Day 15 pulse → Pruitt propagation (new observation): The minor Day 15 rainfall (Ponca zone ~0.41", Pruitt zone ~0.48") produced a small rebound at Ponca on Day 15 (182→207 cfs, +14%) and this pulse propagated to Pruitt, arriving as a +0.08 ft bump centered around 06:00-08:30 CST on Day 16.
This is consistent with the Event 1 Ponca→Pruitt lag of ~15 hours at ~150 cfs. The slightly shorter lag at slightly higher flow fits the velocity-discharge relationship. This provides a 4th data point for the Ponca→Pruitt propagation velocity curve.
4. DOWNSTREAM PROPAGATION:
New data point for velocity model:
| Event | Transit Flow (est.) | Lag (hr) | Velocity (m/s) |
|---|---|---|---|
| Event 1 | ~150 cfs | ~15 hr | ~0.46 |
| Day 15 pulse | ~180 cfs | ~14 hr | ~0.50 |
| Event 3 | ~400-500 cfs | ~7.5 hr | ~0.93 |
| Event 2 | ~1,500-2,000 cfs | ~5.75 hr | ~1.2 |
The Day 15 pulse data point fits well between Event 1 and Event 3, strengthening the velocity-discharge relationship. Confidence upgraded.
5. MULTI-DAY EVENTS: This is Days 5-6 of the extended recession from Event 3 (peaked 3/11-3/12). All gauges are now well into Phase 3 ("deep baseflow") recession. Recession rates today:
| Gauge | Recession Rate (%/hr) | Phase |
|---|---|---|
| Ponca | ~0.83%/hr | Phase 3 (but accelerating due to approaching baseflow floor?) |
| Pruitt | ~0.30%/hr (excluding morning bump) | Phase 3 (slowing further) |
| St. Joe | ~0.10%/hr (very slow, noisy) | Phase 3 (approaching plateau?) |
| Harriet | ~0.56%/hr | Phase 3 |
St. Joe appears to be approaching a baseflow plateau around 580-590 cfs. This is consistent with the large drainage area (1,932 km²) sustaining substantial baseflow from distributed karst springs. Pruitt recession has slowed markedly from 0.42%/hr on Day 15 to ~0.30%/hr today, also suggesting approach to a baseflow floor.
6. ANOMALIES OR SURPRISES:
St. Joe height noise: The ±0.05 ft oscillation in St. Joe height data on 15-minute intervals is notable and not obviously tied to any hydrological cause. CFS shows similar but smaller oscillation. This may be a sensor/turbulence issue that becomes more apparent at low flows. Worth tracking to see if this persists or is a one-day anomaly.
Ponca recession rate: Ponca is declining faster than expected relative to other gauges. From 209 cfs at start of day to 171 cfs represents a ~18% decline in one day, while Pruitt only declined ~7% and St. Joe ~2%. This suggests the upper watershed (Boxley/Ponca zones) is drying out faster than the mid/lower watershed, which is hydrologically reasonable given the smaller drainage area and presumably less karst storage.
Local knowledge comparison: Ponca at 171 cfs is in the "Low but Floatable" range (150-200 cfs). Boxley at 2.41 ft is well below the 3.2 ft threshold for the Boxley-to-Ponca section being "Low but Floatable" per local knowledge. The upper river is effectively too low for recreational floating.