Negligible rainfall across the watershed today. The only area with any measurable QPE was the Richland Creek zone (0.171" average across 2 HUC12s), with Headwaters Richland Creek (0306) receiving 0.117" and Falling Water Creek (0307) receiving 0.224" — the latter being the only HUC12 above 0.1". Peak 1-hr intensity was only 0.133" in Falling Water Creek. All other gauge zones received effectively zero precipitation (<0.05"). This is not a rainfall event — it's trace/scattered moisture with no hydrological significance.
No new rises at any gauge. All seven gauges continued their monotonic recession from Event 2 (March 7-8). No events flagged by the automated system.
End-of-day recession status (all CDT):
| Gauge | SOD Value | EOD Value | Change | Current Status |
|---|---|---|---|---|
| Boxley | 2.88 ft | 2.75 ft | -0.13 ft | Receding (still +0.85 ft above 1.90 ft baseflow) |
| Ponca | 274 cfs | 226 cfs | -48 cfs | Optimal (>200) |
| Pruitt | 5.20 ft / 552 cfs | 4.79 ft / 402 cfs | -0.41 ft / -150 cfs | Optimal (>200) |
| St. Joe | 6.51 ft / 1,800 cfs | 5.69 ft / 1,190 cfs | -0.82 ft / -610 cfs | Optimal (>200) |
| Harriet | 6.20 ft / 2,330 cfs | 5.43 ft / 1,520 cfs | -0.77 ft / -810 cfs | Optimal (>200) |
| Richland | 2.03 ft | 1.84 ft | -0.19 ft | Receding |
| Bear Creek | 2.76 ft / 33.5 cfs | 2.64 ft / 24.2 cfs | -0.12 ft / -9.3 cfs | Receding |
Recreational context: All mainstem gauges from Ponca through Harriet remain in their Optimal ranges. Ponca (226 cfs) is approaching its lower Optimal boundary (200 cfs) and will likely drop below it within 1-2 days without new rainfall. Pruitt (402 cfs) and downstream gauges have substantial headroom above their Optimal thresholds. This is day 3 of excellent paddling conditions from Pruitt downstream.
None. No significant rainfall occurred.
Not applicable — no new rises. However, the ongoing recession allows refinement of recession characteristics.
This is an excellent opportunity to characterize the full recession curve from Event 2 with no new rainfall confounding the signal.
Extended recession rates (from Event 2 peak through EOD 3/09):
| Gauge | Peak CFS | Peak Time | EOD 3/09 CFS | Hours Since Peak | Total Recession | Avg Rate |
|---|---|---|---|---|---|---|
| Ponca | 2,120 | 3/07 07:30 CST | 226 | ~63 hr | -1,894 cfs | ~30 cfs/hr |
| Pruitt | 2,610 | 3/07 13:15 CST | 402 | ~58 hr | -2,208 cfs | ~38 cfs/hr |
| St. Joe | 3,230 | 3/08 ~03:30 CDT | 1,190 | ~43 hr | -2,040 cfs | ~47 cfs/hr |
| Harriet | 3,050 | 3/08 ~11:30 CDT | 1,520 | ~35 hr | -1,530 cfs | ~44 cfs/hr |
Key observation — recession deceleration: Comparing today's recession rates to yesterday's (Day 8 analysis):
| Gauge | Day 1 Recession Rate (3/08) | Day 2 Recession Rate (3/09) | Ratio |
|---|---|---|---|
| Ponca | ~45 cfs/hr | ~2.0 cfs/hr | 0.04x |
| Pruitt | ~93 cfs/hr | ~6.5 cfs/hr | 0.07x |
| St. Joe | ~69 cfs/hr | ~28 cfs/hr | 0.41x |
| Harriet | ~55 cfs/hr | ~34 cfs/hr | 0.62x |
This dramatically confirms exponential recession — the rate drops roughly proportionally to the remaining excess flow above baseflow. The upstream gauges (Ponca, Pruitt) have already transitioned to slow groundwater-dominated recession. The downstream gauges (St. Joe, Harriet) are still in the steeper portion of their recession curves due to their later peaks and larger sustained baseflow contributions from the 1,342 km² and 2,775 km² drainage areas.
Boxley pool drainage update: 2.88 → 2.75 ft over 24 hours = 0.013 ft/hr = 0.54 ft/day. This is identical to the rate observed on 3/08, confirming a remarkably steady pool-drainage rate. At this rate, Boxley will reach pre-event baseflow (1.90 ft) in approximately 1.6 more days (~March 11). However, the rate may slow further as pool levels drop, so 2-3 days is more realistic.
Recession half-life estimates (NEW):
Using the two-day recession data to estimate the time for each gauge to lose half its excess flow above baseflow:
| Gauge | Baseflow | Post-Peak Half-Life (estimated) |
|---|---|---|
| Ponca | ~84 cfs | ~12-15 hr (fast; small watershed, 390 km²) |
| Pruitt | ~64 cfs | ~12-15 hr (similar to Ponca; 513 km²) |
| St. Joe | ~165 cfs | ~20-24 hr (slower; large composite watershed, 1,932 km²) |
| Harriet | ~172 cfs | ~24-30 hr (slowest; largest area, 2,775 km²) |
Richland Creek gauge data gaps: The Richland Creek gauge continues to show intermittent data gaps (75 readings vs expected 96). Multiple timestamps are missing throughout the day. This has been a persistent pattern since the start of the study. It does not affect interpretation today (simple recession), but will be problematic during future events when we need continuous data for signal separation. Worth noting for data quality tracking.
Ponca approaching threshold: At 226 cfs and declining ~2 cfs/hr, Ponca will cross below its Optimal threshold (200 cfs) sometime on March 10, likely by midday. It will then enter the "Low but Floatable" range (150-200 cfs). This is valuable for recreational planning — the Ponca-to-Pruitt section window from Event 2 is closing.
Local knowledge comparison — Richland Creek recreational levels: The Richland gauge peaked at 2.55 ft during Event 2. Per local knowledge, Richland Creek (upper section) becomes "low but floatable" at 3.2 ft. So Event 2, despite being a Tier 3 event on the mainstem, did NOT produce runnable conditions on Upper Richland — the 1.24" of rain in the Richland HUC12s was insufficient. This provides a useful calibration point: ~1.2" across Richland HUC12s with wet antecedent → peak 2.55 ft (0.65 ft below floatable threshold). Reaching the 3.2 ft threshold would likely require 2-3"+ concentrated in the Richland sub-basin, consistent with the March 2024 reference event where 4-8" produced extreme flooding.