Light, scattered rainfall returned across the watershed today after 3 consecutive dry days (Apr 13-14 had zero QPE everywhere). The rain was concentrated in the upper watershed and Harriet direct zone, with very light amounts in the middle and lower watershed.
Zone totals (area-weighted averages): - Boxley: 0.468" (peak 0.287"/hr at ~23:00 CST Apr 15) - Ponca: 0.264" (peak 0.109"/hr) - Pruitt: 0.172" (peak 0.095"/hr) - St. Joe: 0.155" (peak 0.186"/hr — this is the HUC12 max, not zone average peak) - Harriet: 0.111" (peak 0.105"/hr) - Richland: 0.092" - Bear Creek: 0.068" - Ungauged: 0.161"
Spatial pattern: Rain was heaviest in Boxley HUC12 (0.468") and the Little Buffalo complex (Shop Creek 0.127", Headwaters LB 0.346", Henson 0.203", Outlet LB 0.231"). The rain arrived in two loosely timed pulses: a minor afternoon/evening pulse around 13:00-14:00 UTC (07:00-08:00 CST) concentrated in Beech Creek (0.295"), and a second broader pulse around 19:00-04:00 UTC (13:00-23:00 CST) with peaks in the evening.
Gauge-measured precipitation: Pruitt recorded 0.03", St. Joe recorded 0.12", Harriet recorded 0.15". These are consistent with the QPE pattern showing heavier amounts toward the headwaters and Harriet direct zone.
Assessment: This is a sub-threshold to marginal event for most gauges. Boxley at 0.468" is in the range where we've previously seen marginal responses (0.4-0.5" on Mar 15 produced a barely detectable pulse). However, antecedent conditions are now significantly drier than any previous rain event — 7-day totals are 0.07-0.67" across the watershed, and gauges have been declining for 11+ days since Event 4. This strongly favors a non-detection or minimal response outcome.
No significant rises detected at any gauge. All gauges continued their Event 4 recession or stabilized at seasonal baseflow.
End-of-day values (Day 13 of Event 4 recession):
| Gauge | EOD Apr 14 | EOD Apr 15 | Change | Daily Rate |
|---|---|---|---|---|
| Boxley | 2.19 ft | 2.16 ft | -0.03 ft | ~1.4%/day (height) |
| Ponca | 120 cfs | 117 cfs | -3 cfs | ~2.5%/day |
| Pruitt | 138 cfs / 3.85 ft | 124 cfs / 3.79 ft | -14 cfs / -0.06 ft | ~10.1%/day |
| St. Joe | 324 cfs / 3.94 ft | 304 cfs / 3.88 ft | -20 cfs / -0.06 ft | ~6.2%/day |
| Harriet | 431 cfs / 4.05 ft | 396 cfs / 3.99 ft | -35 cfs / -0.06 ft | ~8.1%/day |
| Richland | 1.29 ft | 1.25 ft | -0.04 ft | — |
| Bear Creek | 21.0 cfs / 2.23 ft | 19.8 cfs / 2.21 ft | -1.2 cfs / -0.02 ft | ~5.7%/day |
Key observations: - Boxley at 2.15-2.16 ft is now well below pre-Event 4 levels (1.84 ft pre-Event 4, but has been higher since). Appears to be approaching a new seasonal low. The late-day QPE of 0.468" in the Boxley HUC12, with the peak intensity at ~23:00 CST, has not yet produced any detectable response — Boxley was flat at 2.15-2.16 ft through end of day. Any response would appear tomorrow if at all. - Ponca at 117 cfs is now firmly below the "Too Low" threshold (<150 cfs). It has been below this since ~Apr 12. - Pruitt at 124 cfs is now approaching the "Low but Floatable" floor (100 cfs). The Day 13 recession rate of 10.1% is notably higher than Day 12's 12.7% — wait, that's actually lower. Let me recalculate: Day 12 EOD was 138 cfs, Day 13 EOD is 124 cfs. (138-124)/138 = 10.1%. Day 12 was (158-138)/158 = 12.7%. So Day 13 rate is lower than Day 12. This could be genuine deceleration as Pruitt approaches baseflow, or could be noise in the CFS quantization. The height decline was -0.06 ft both days, suggesting a steady rate. - St. Joe Day 13 rate: (324-304)/324 = 6.2%. This is notably lower than Day 12's 10.0%. This could be the beginning of further recession deceleration as St. Joe approaches the 200 cfs threshold, or it could be the first hint that the afternoon's light rain (~0.12-0.15" across St. Joe zone) is slightly retarding the recession. I lean toward natural deceleration — 6.2% at 304 cfs makes physical sense as the recession curve flattens. - Harriet Day 13 rate: (431-396)/431 = 8.1%. This is between Day 11's 8.3% and Day 12's 11.1%, so within the established range.
No detectable rainfall-response pairs today. The Boxley rain (0.468") arrived late in the day (peak at ~23:00 CST) and any response would not appear until Apr 16.
Prediction for tomorrow: Given 0.468" in the Boxley HUC12 with 0.287"/hr peak intensity but on very dry antecedent conditions (only 0.665" in 7-day window, and the gauge has been declining for 11+ consecutive days), I predict either: - No detectable response (if the "pool filling" effect described in local knowledge absorbs this amount), or - A very marginal response of +0.02-0.05 ft at Boxley, comparable to or less than the March 15 pulse (0.4-0.5" → barely detectable).
This will be an important test of the non-linear Boxley response hypothesis and the local knowledge about pool-filling after dry spells.
No propagation to track today. All gauges declining monotonically.
Event 4 recession continues — Day 13.
Recreational duration tracking — finalized/updated: - Ponca: Crossed below "Too Low" (<150 cfs) around Apr 11-12. Now at 117 cfs. No recreational significance. - Pruitt: At 124 cfs, still in "Low but Floatable" (100-200 cfs). Projected to reach 100 cfs threshold in ~2-3 days at current rates (~Apr 17-18). - St. Joe: At 304 cfs, still comfortably in "Optimal" (200-8000 cfs). With Day 13 rate of 6.2%, projected to reach 200 cfs in ~6-8 days (~Apr 21-23). However, today's light rain may slow this further. Total Optimal duration from Event 4 now projected at ~350-430 hours (15-18 days). - Harriet: At 396 cfs, in "Optimal" (200-9370 cfs). At 8.1%/day, projected to reach 200 cfs in ~8-10 days (~Apr 23-25). Total Optimal duration projected at ~420-500 hours (17.5-21 days).
Bear Creek post-rating-curve baseline establishing: With the new rating curve (updated Apr 14), Bear Creek baseflow at 2.23 ft is ~21 cfs and at 2.21 ft is ~19.8 cfs. This gives us a height-discharge relationship data point: 0.02 ft corresponds to ~1.2 cfs at baseflow, or about 60 cfs/ft. This is useful for future events.
St. Joe recession deceleration: The Day 13 rate of 6.2% is the lowest clean recession rate we've observed at St. Joe. This is consistent with the hypothesis that St. Joe's recession follows an exponential decay of the rate itself (40% → 29% → 21% → ... → 10% → 6.2%). The watershed's karst storage is now dominating flow, with quick-flow essentially exhausted. This suggests St. Joe could sustain Optimal flows for longer than previously projected.
No comparison to local knowledge entries today — no feeder creeks or tributary sections are near runnable levels.