Day 19 (2026-03-19) — Continued dry recession, no precipitation
Zero precipitation across all 37 HUC12s. This is the third consecutive day with no rainfall. The 7-day antecedent precip has dropped substantially as the Event 2/3 rainfall rolls out of the 7-day window: - Boxley: 0.161" (down from 0.972" yesterday) - Ponca zone: 0.22-0.56" (down from 0.46-1.23") - Pruitt zone: 0.44-0.52" (down from 0.49-1.03") - St. Joe zone: 0.14-0.52" (down from 0.56-1.07") - Richland: 0.27-0.33" (down from 0.84-0.88") - Bear Creek: 0.24-0.38" (down from 0.71-0.94%) - Harriet: 0.15-0.19" (down from 0.42-0.61")
This is now the driest antecedent condition of the entire study — most HUC12s below 0.3" 7-day, many below 0.2". The watershed is entering a true dry-down state.
All gauges continued recession with no significant rises. End-of-day values and daily changes:
| Gauge | Start of Day | End of Day | Change | Rate |
|---|---|---|---|---|
| Boxley | 2.26 ft | 2.21 ft | -0.05 ft | Steady decline |
| Ponca | 145 cfs | 136 cfs | -9 cfs (-6.2%) | Continuing slow decline |
| Pruitt | 4.13 ft / 200 cfs | 4.05 ft / 177 cfs | -0.08 ft / -23 cfs (-11.5%) | Crossed below Optimal (200 cfs) threshold |
| St. Joe | 4.25 ft / 429 cfs | 4.13 ft / 394 cfs | -0.12 ft / -35 cfs (-8.2%) | Active recession continues |
| Harriet | 4.22 ft / 535 cfs | 4.12 ft / 473 cfs | -0.10 ft / -62 cfs (-11.6%) | Steep decline continues |
| Richland | 1.24 ft | 1.20 ft | -0.04 ft | Approaching study minimum |
| Bear Creek | 2.42 ft / 12.4 cfs | 2.40 ft / 11.3 cfs | -0.02 ft / -1.1 cfs (-8.9%) | New study low |
None — no rainfall occurred.
No propagation events to track.
Extended recession analysis (Day 8 post Event 3 peak, Day 12 post Event 2 peak):
Recession rates by gauge (computed as approximate %/hr from daily averages):
| Gauge | Day 18 Rate | Day 19 Rate | Day 19 CFS | Status |
|---|---|---|---|---|
| Ponca | ~0.27%/hr | ~0.27%/hr | 136 | Still declining — has NOT stabilized. Below "Low but Floatable" (150) threshold as of midday |
| Pruitt | ~0.33%/hr | ~0.56%/hr | 177 | Accelerating decline — dropped below Optimal (200 cfs) early in the day, now in "Low but Floatable" |
| St. Joe | ~0.70%/hr | ~0.37%/hr | 394 | Slowing — rate dropped by nearly half |
| Harriet | ~0.70%/hr | ~0.49%/hr | 473 | Slowing somewhat — still declining but rate easing |
Key observations:
Ponca has dropped below 150 cfs (Too Low threshold). At 136 cfs end-of-day, Ponca is now in "Too Low" territory for recreation. This is significant — it's the first time during the study that Ponca has fallen below 150 cfs. The baseflow floor estimate of 130-145 cfs from Day 18 needs revision; we're at 136 and still declining at ~0.27%/hr with no sign of stabilization.
Pruitt crossed below Optimal (200 cfs) early on Day 19 and continued declining to 177 cfs. It's now in "Low but Floatable" (100-200 cfs). The Pruitt recession rate actually increased from Day 18 (0.33%/hr → 0.56%/hr), which is unusual — this may reflect the Ponca input declining below a threshold where Pruitt's local springs can't compensate.
Pruitt-Ponca discharge gap is narrowing: Pruitt at 177 vs Ponca at 136 = 41 cfs gain across the Pruitt zone. This was ~60 cfs on Day 18. The shrinking gap suggests interflow from Cove Creek and Hoskin Creek HUC12s is depleting.
St. Joe recession is slowing — from 0.70%/hr on Day 18 to 0.37%/hr on Day 19. At 394 cfs it may be approaching a baseflow regime, but I'm cautious given the Harriet plateau lesson from Days 15-17.
Harriet recession slowed slightly but remains steep at 0.49%/hr. At 473 cfs, the St. Joe-to-Harriet gain is now 473-394 = 79 cfs, down from 535-429 = 106 cfs yesterday. This is consistent with the Bear Creek tributary continuing to decline (now at its lowest recorded value of 11.3 cfs).
Ponca baseflow floor estimate needs further revision downward. On Day 18 I estimated 130-145 cfs. Ponca is now at 136 and still declining at the same rate as yesterday. There's no sign of stabilization. I'm revising the estimate to 120-135 cfs but with LOW confidence — we simply haven't seen enough dry days yet to identify the true floor.
Pruitt recession acceleration is notable. I would have expected Pruitt's recession to slow as it approaches baseflow. Instead it accelerated. This is consistent with the local knowledge about channel scouring near the Pruitt gauge causing flow to prefer river right — at low stages, the gauge may be reading lower than true discharge. Alternatively, the karst springs feeding Pruitt's gain over Ponca may have a threshold below which they decline nonlinearly.
Recreational status summary: As of end-of-day, Ponca is "Too Low" (136 cfs < 150), Pruitt is "Low but Floatable" (177 cfs, between 100-200), St. Joe is solidly "Optimal" (394 cfs, well above 200), and Harriet is "Optimal" (473 cfs, well above 200). The recreational gradient — Too Low upstream, Optimal downstream — reflects the delayed recession of the larger downstream watersheds.