Day 31 (2026-03-31) — End of Month 1
Zero precipitation across the entire watershed for the fourth consecutive day (Days 28-31). All 37 HUC12s recorded 0.0" total. The 7-day antecedent precipitation remains unchanged from Days 29-30 at 0.10-0.40" (all from the March 27 trace event, which will begin rolling out of the 7-day window tomorrow). The dry spell now extends to 23 consecutive days since the last meaningful precipitation (Event 3 on March 11-12), with only the trace 0.1-0.4" on Day 27 interrupting complete zero conditions.
All gauges continued slow baseflow recession. New study-low values recorded at multiple gauges:
| Gauge | Day 30 End | Day 31 End | Change | New Study Low? |
|---|---|---|---|---|
| Boxley | 1.80 ft | 1.78 ft | -0.02 ft | Yes (prev 1.80) |
| Ponca | 85.1 cfs | 83.7 cfs | -1.4 cfs | Yes (prev 85.1) |
| Pruitt | 3.50 ft / 55.1 cfs | 3.48 ft / 52.3 cfs | -0.02 ft | Approaching (low was 3.43 intraday) |
| St. Joe | 3.46 ft / 179 cfs | 3.45 ft / 175 cfs | -0.01 ft / -4 cfs | Yes — height 3.42 intraday, CFS 165 intraday |
| Harriet | 3.59 ft / 197 cfs | 3.57 ft / 189 cfs | -0.02 ft / -8 cfs | Yes (prev 3.59/197) |
| Richland | 0.90 ft | 0.89 ft | -0.01 ft | Yes — intraday low 0.88 ft |
| Bear Creek | 2.28 ft / 4.6 cfs | 2.28 ft / 4.6 cfs | ~0 / 0 | Approaching — 2.27 ft & 4.19 cfs frequent in PM |
Recreational status (Day 31): - Ponca: 83.7 cfs — Too Low (<150) - Pruitt: ~50 cfs reported — Too Low (<100), but CFS unreliable at these levels - St. Joe: 175 cfs — Low but Floatable (40-200 range), trending toward Too Low - Harriet: 189 cfs — Low but Floatable (60-200 range), trending toward Too Low
Key observations:
Ponca reached a new low of 83.7 cfs, breaking below the previous floor estimate of ~84-86 cfs. This appeared first at 21:00 CST and then again at 23:30. The reading is only 1.4 cfs below the previous minimum so it may represent a slight downward revision to the baseflow floor, or Ponca may still be very slowly declining. The fact that Ponca spent the vast majority of the day locked at 85.1 cfs (with only occasional 86.4 spikes) and only touched 83.7 twice suggests the floor is approximately 83-85 cfs, revised slightly downward from the previous 84-86 estimate.
St. Joe showed notable intraday scatter — height ranged 3.42-3.49 ft (0.07 ft range) and CFS ranged 165-187 (22 cfs range) with no precipitation driver. The 3.42 ft reading at 11:30 CST is the lowest height observed at St. Joe during the entire study. CFS touched 165 cfs, approaching the "Too Low" threshold of 40 cfs (still well above). The mean CFS has clearly declined from ~195 on Day 29 to ~179 on Day 30 to ~176 on Day 31. At the current ~3.5%/day decline rate, St. Joe will cross below the Low-but-Floatable threshold (200 cfs lower bound) — wait, it already has. St. Joe mean CFS is now ~176, already in "Low but Floatable" territory (40-200).
Harriet showed a clearer step-down today: height dropped from 3.59 to 3.57 ft, and CFS dropped from the 197-210 range to 189-197. The first half of the day held at 3.59/197, then stepped down to 3.57-3.58/189-193 in the afternoon. Harriet is now at the boundary between Optimal (≥200) and Low-but-Floatable. At its current end-of-day CFS of 189, it has dropped below the 200 cfs Optimal threshold.
Bear Creek showed a subtle shift toward lower values in the PM hours — height readings of 2.27 and CFS readings of 4.19 became dominant after ~17:00. This may represent Bear Creek finally approaching its baseflow floor at approximately 2.27 ft / 4.2 cfs.
Richland Creek continues to show gaps in its data record (only 64 readings vs. 95+ for other gauges). The intraday low of 0.88 ft is a new study minimum. The karst-related noise (±0.03 ft) persists but the central tendency has clearly declined from ~0.92 (Day 29) to ~0.90 (Day 30) to ~0.89 (Day 31).
None — no precipitation.
No flood wave propagation to track. However, the baseflow recession provides useful information about baseflow connectivity between gauges. Ponca (83.7 cfs) continues to show dramatically higher CFS than Pruitt (52.3 cfs), which remains anomalous for a gaining reach. This 37% apparent loss is consistent with the local knowledge about channel scouring moving flow away from the Pruitt gauge, and the anomaly has been persistent for the entire dry period.
This is Day 23 of the post-Event 3 dry recession and Day 4 of the post-March 27 complete zero-precipitation period. The extended recession continues to refine baseflow floor estimates:
Updated baseflow floor estimates (Day 31): | Gauge | Estimated Floor | Confidence | Evidence | |-------|----------------|------------|---------| | Boxley | ~1.77-1.78 ft | Moderate | Still declining ~0.01 ft/day; not yet fully stabilized | | Ponca | ~83-85 cfs | High | Nearly flat for 5+ days, touched 83.7 today | | St. Joe | Unknown, <165 cfs | Low | Still declining ~3-4%/day, not approaching floor | | Harriet | Unknown, <189 cfs | Low | Still declining ~3-4%/day, not approaching floor | | Bear Creek | ~2.27 ft / ~4.2 cfs | Moderate | Approaching stabilization | | Richland | ~0.87-0.88 ft | Low-Moderate | Still declining, noisy data |
St. Joe and Harriet are still not approaching their baseflow floors after 23 days without meaningful rain. This contrasts sharply with Ponca, which reached its floor ~10 days ago. The difference likely reflects the much larger contributing areas (1,932 km² for St. Joe vs. 298 km² for Ponca) — larger watersheds have longer memory due to deeper groundwater storage. This has implications for the "antecedent moisture" framework: even after 23 dry days, St. Joe and Harriet retain meaningful baseflow from deep aquifer/karst storage, while the upper watershed has been fully depleted to spring-fed baseflow.
Month 1 summary note: March ends with no rain in the forecast (implied by the sustained pattern). The study has observed 3 events, 1 sub-threshold pulse, and 1 non-detection across 31 days. The first third of the study has provided excellent recession and baseflow characterization but only limited event data. April-May will need to provide the moderate and heavy events necessary to populate the Tier 2-4 transfer functions, particularly for the St. Joe zone tributaries (Big Creek, Little Buffalo, Cave Creek) and Bear Creek, which have yet to produce a single clear local response event.