Today (April 10) marks the end of the 7-day dry period following Event 4, with light-to-moderate rainfall arriving in the late afternoon/evening, concentrated in specific zones:
Significant rainfall (>0.4"): - Water Creek (Harriet zone, HUC12 0408): 1.098" — peak 1hr intensity 0.659"/hr at ~21:02 UTC (16:02 CST). This is the heaviest cell today. - Tomahawk Creek (Harriet zone, HUC12 0407): 0.780" — peak 0.536"/hr - Cove Creek (Pruitt zone, HUC12 0204): 0.657" — peak 0.507"/hr - Spring Creek (Harriet zone, HUC12 0409): 0.589" - Boxley (HUC12 0201): 0.553" — peak 0.297"/hr - Dry Creek (Harriet zone, HUC12 0406): 0.470"
Moderate rainfall (0.1-0.4"): - Rocky Hollow (St. Joe, HUC12 0402): 0.273" - Headwaters LB (Little Buffalo, HUC12 0102): 0.237" - Smith Creek (Ponca, HUC12 0203): 0.212" - Big Creek-Buffalo (St. Joe, HUC12 0303): 0.174" - Whiteley Creek (Ponca, HUC12 0205): 0.173" - Shop Creek (St. Joe, HUC12 0101): 0.132" - Outlet Richland (St. Joe, HUC12 0308): 0.115" - Calf Creek (St. Joe, HUC12 0401): 0.105"
Minimal/trace (<0.1"): - Richland zone: 0.034" average — essentially nothing - Bear Creek zone: 0.038" average — essentially nothing - Most St. Joe interior HUC12s: <0.1"
Spatial pattern: This is a lower watershed / Harriet zone storm, with the heaviest concentrations in the direct Harriet sub-watershed (Water Creek, Tomahawk Creek, Spring Creek). A secondary cell hit Cove Creek in the Pruitt zone. Boxley got moderate rain. The core St. Joe tributaries (Big Creek complex, Little Buffalo, Richland, Cave Creek) were largely missed.
Timing: All rainfall concentrated in a ~4-6 hour window from approximately 14:00-20:00 UTC (09:00-15:00 CST) based on peak 1hr times clustering around 19:02-23:02 UTC.
Zone averages: Harriet 0.604", Boxley 0.553", Pruitt 0.349", Ponca 0.159", St. Joe 0.108", Bear Creek 0.038", Richland 0.034"
Gauge precip recordings: St. Joe gauge recorded 0.34", Harriet gauge recorded 0.72", Pruitt gauge recorded 0.00" (interesting — the 0.657" in Cove Creek may not have extended to the gauge location).
Recession continues at all mainstem gauges (Day 7 of dry recession before evening rain):
End-of-day values compared to yesterday's end-of-day:
| Gauge | Apr 9 EOD | Apr 10 EOD | Change | Status |
|---|---|---|---|---|
| Boxley | 2.43 ft | 2.39 ft* | -0.04 ft | Recession continued; minor bump at 21:00 (+0.03 ft) |
| Ponca | 157 cfs | 143 cfs | -14 cfs (-8.9%) | Crossed below Too Low (<150 cfs) at ~09:45 CST |
| Pruitt | 221 cfs | 194 cfs* | -27 cfs | Crossed below Optimal (<200 cfs) at ~11:45 CST |
| St. Joe | 613 cfs | 512 cfs | -101 cfs (-16.5%) | Still Optimal (well above 200) |
| Harriet | 793 cfs | 749 cfs* | -44 cfs | Still Optimal; notable response starting ~16:30 |
| Richland | 1.68 ft | 1.57 ft | -0.11 ft | Continuing recession |
| Bear Creek | 10.6 cfs | 7.2 cfs | -3.4 cfs (-32%) | Approaching pre-event baseline (~4.2 cfs) |
*End of day values affected by late-day rainfall response
Key threshold crossings today: - Ponca crossed below 150 cfs (Too Low) at ~09:45 CST. This confirms the Event 4 Low-but-Floatable duration at Ponca: crossed below 200 cfs ~18:00 Apr 7, crossed below 150 cfs ~09:45 Apr 10 = ~64 hours in Low-but-Floatable, and total floatable duration (>150 cfs) from ~11:00 Apr 4 to ~09:45 Apr 10 = ~143 hours (~6 days). - Pruitt crossed below 200 cfs (below Optimal, into Low-but-Floatable) at ~11:45 CST. This confirms the Event 4 Optimal duration at Pruitt: from ~20:30 Apr 4 to ~11:45 Apr 10 = ~135 hours (~5.6 days).
Harriet late-day response: The most interesting gauge signal today is at Harriet. After declining steadily all day from 4.59 ft / 793 cfs to a low of 4.47 ft / 705 cfs at ~16:00 CST, Harriet shows a clear reversal: - 16:00 CST: 4.47 ft / 705 cfs (day low) - 16:45 CST: 4.53 ft / 749 cfs - 17:15 CST: 4.57 ft / 778 cfs (local peak, +0.10 ft / +73 cfs in 75 min) - Then oscillates 4.53-4.59 ft through end of day, settling at ~4.53 ft / 749 cfs
This is a clear rainfall response at Harriet. The 0.72" recorded at the Harriet gauge itself, plus 1.098" on Water Creek, 0.780" on Tomahawk Creek, 0.589" on Spring Creek, and 0.470" on Dry Creek — all direct Harriet-zone tributaries — produced a modest but definite rise that interrupted the recession. The +0.10 ft / +73 cfs rise is small but unambiguous.
Signal separation check: Bear Creek gauge is flat/declining all day (2.33 ft / 7.2 cfs at end of day, QPE only 0.038" on Bear Creek zone). Richland also flat/declining. This confirms the rise at Harriet is from direct Harriet-zone rainfall, not upstream propagation (which wouldn't arrive this quickly anyway — St. Joe is still declining).
Boxley mini-bump: Boxley shows a small bump from 2.36 ft at 19:00 to 2.39 ft at 21:00-23:15 CST (+0.03 ft). The 0.553" of rain on the Boxley HUC12 with 0.297"/hr peak intensity produced this tiny response. This is at the detection threshold. With antecedent moisture moderately elevated (1.58" 7-day), this 0.55" is only barely detectable. This is consistent with our detection threshold estimate of ~0.5" for Boxley on moderate antecedent.
Pruitt height stabilization pattern — Day 3: On Apr 10, Pruitt height declined from 4.14 ft to a low of 4.04 ft around 19:45, then stabilized/bounced to 4.05-4.06 ft through end of day. This is the third consecutive day showing this afternoon stabilization pattern. Today's may be partly influenced by the 0.657" Cove Creek rainfall entering the system, but it could also be the same flow redistribution artifact noted previously.
Harriet zone direct rainfall → Harriet gauge: - Rainfall: ~0.6" average across Harriet zone (peak Water Creek 1.098"), peaking ~15:00-16:00 CST - Response: +0.10 ft / +73 cfs at Harriet starting ~16:00-16:30 CST - Lag time: ~0-1 hours (very short — local rainfall on direct tributaries) - Transfer ratio: 0.6" zone average → +0.10 ft / +73 cfs. This is modest but the response was on top of already elevated baseflow (705 cfs). - Antecedent: 7-day precip 1.7-1.8" in Harriet zone, gauges still well above pre-event baseline - This is our first observation of a Harriet-zone-only rainfall event — previous events all had significant upstream contributions. This provides a calibration point for the direct Harriet sub-watershed response independent of mainstem propagation.
Boxley rainfall → Boxley gauge: - Rainfall: 0.553" on Boxley HUC12, peak 0.297"/hr at ~17:02 CST (23:02 UTC) - Response: +0.03 ft at Boxley around 20:15-21:00 CST - Lag time: ~3-4 hours from rainfall peak - This is at the detection threshold. Confirms: 0.55" on moderate antecedent (1.58" 7-day) produces barely detectable response (+0.03 ft) at Boxley. Consistent with previous estimates.
No multi-gauge propagation to track. The Harriet response is from direct local rainfall, and the Boxley bump is too small to propagate detectably downstream.
Prediction for Apr 11: The 0.657" on Cove Creek (Pruitt zone) should produce a small response at Pruitt, possibly 12-24 hours after the rainfall centroid (~16:00 CST Apr 10), so watch for Pruitt stabilization or slight rise on Apr 11 morning. The Harriet bump will propagate downstream but Harriet is the lowest gauged point so we can't track it further.
This is primarily a recession-tracking day (Day 7 from Event 4 peak), with new rainfall arriving late. The recession rates continue to decelerate:
Day 7 recession rates (before evening rain effects): - Boxley: ~2.6%/day (height) — further deceleration from Day 6's ~3.9% - Ponca: ~8.9%/day — consistent with Day 5-6 asymptote of ~8% - Pruitt: ~11.5%/day (using morning values) — continued deceleration from ~13% - St. Joe: ~16.5%/day — continued deceleration from ~18.6% - Harriet: ~10.6%/day (using pre-rain morning values) — notable deceleration from ~19.9%
Bear Creek approaches baseline: At 7.2 cfs, Bear Creek is now only 71% above pre-event baseline (4.2 cfs), down from 152% yesterday. Expected to reach baseline ~Apr 12-13, consistent with previous estimate.
Harriet recession rate dramatically slower than expected: At ~10.6%/day on Day 7, Harriet has decelerated much more than predicted. The previous Day 5 rate was ~19.9%/day. This suggests Harriet's massive upstream drainage area (2,775 km² total) provides very long-duration baseflow support. At 705-749 cfs (pre-rain/post-rain), Harriet remains well within Optimal and will likely stay above 200 cfs for many more days. Previous projection of ~Apr 16-17 for crossing 200 cfs now looks conservative — it may hold Optimal until Apr 20+ at this rate.
Pruitt gauge precip = 0.0" but Cove Creek got 0.657": The Pruitt tipping bucket recorded zero precipitation, but MRMS shows 0.657" just upstream in the Cove Creek HUC12 with 0.507"/hr peak intensity. This highlights either: (a) the rain cell was localized enough to miss the gauge by a few km, or (b) MRMS is overestimating. Given that we also have 0.041" on Hoskin Creek (the other Pruitt HUC12), this appears to be a very localized cell in the Cove Creek sub-basin that didn't extend to the Pruitt gauge location. This is a useful calibration point for understanding the spatial resolution needed for QPE in this watershed.
Event 4 Optimal duration at Pruitt confirmed: ~5.6 days. This is remarkably long for a Tier 2 event and reflects both the magnitude of the compound three-pulse rainfall and the baseflow sustenance from the 513 km² drainage area.