Today (April 3) saw a spatially concentrated rainfall event in the southeastern portion of the watershed, with essentially zero precipitation in the upper watershed. This is the most spatially asymmetric event of the study to date.
Heaviest rainfall zones: - Bear Creek zone: 0.671" average — Headwaters Bear Creek (0403) 0.709" (peak 0.391"/hr), Outlet Bear Creek (0404) 0.634" (peak 0.348"/hr) - Richland zone: 0.621" average — Headwaters Richland Creek (0306) 0.656" (peak 0.336"/hr), Falling Water Creek (0307) 0.585" (peak 0.382"/hr) - Harriet zone: 0.421" average — Brush Creek (0405) 0.532", Spring Creek (0409) 0.490", Water Creek (0408) 0.369", Tomahawk Creek (0407) 0.362", Dry Creek (0406) 0.353" - St. Joe zone (distributed): 0.184" average — but highly variable. Cave Creek (0305) 0.476", Calf Creek (0401) 0.474", Outlet Richland (0308) 0.460", Rocky Hollow (0402) 0.316", Headwaters Big Creek (0302) 0.315". Several St. Joe HUC12s received near-zero. - Upper watershed (Boxley/Ponca/Pruitt): effectively zero — Boxley 0.005", Ponca 0.001", Pruitt 0.000"
Timing: Peak 1-hour intensities occurred very late in the day, around 03:00-04:00 UTC on April 4 (10-11 PM CDT April 3). This means the bulk of the rain fell in the last 2-3 hours of the data window. Most gauge responses will appear on Day 35 (April 4).
Spatial pattern: Rain concentrated in a SE band covering Richland, Bear Creek, lower St. Joe tributaries (Cave Creek, Calf Creek), and Harriet zone HUC12s. The upper mainstem was completely dry.
Boxley (07055646): Continued slow rise from yesterday's April 2 rain response. Rose from 1.81 ft at midnight to peak 1.88 ft around 10:45-12:30, then slowly receded to 1.85 ft by end of day. Total rise from April 2 pre-event (1.76 ft) is now +0.12 ft over ~36 hours. This is the continued response to the 0.52" Boxley zone rain from April 2, not today's trace amounts. The gradual nature (12+ hours of rise) is consistent with local knowledge about pool-filling in the headwaters section.
Ponca (07055660): Rose from 83.7 cfs at start of day to 87.8 cfs by late afternoon, stabilizing there. This +4.1 cfs (+5%) is a marginal rise, likely the delayed propagation of the Boxley response from April 2 rain arriving at Ponca. The timing (~12-18 hours after Boxley began rising on 4/02) is consistent with the low-flow Boxley→Ponca lag of 4-5 hours plus the slow nature of the Boxley rise itself.
Pruitt (07055680): No significant response. Ranged 41.7-49.5 cfs (noise floor). New study-low discharge of 41.7 cfs recorded at 14:45. Zero local precipitation. Late-day slight firming (46-48 cfs range by 19:00-21:00) could be early arrival of Ponca pulse, but within noise.
St. Joe (07056000): Slight downward trend through the day, from ~175 cfs at start to a low of 153 cfs at 16:00 (3.38 ft — near study low). Then slight firming to ~165-169 cfs by end of day. The gauge precip recorded 0.48" — consistent with QPE for the St. Joe area. No clear runoff response yet from today's rain, which is expected since the rain fell in the last 2-3 hours of the day. Watch for response on Day 35.
Harriet (07056700): Gentle rise through the day: 3.53 ft / 172 cfs at start, rising to 3.57 ft / 189 cfs by 22:45. The +0.04 ft / +17 cfs rise appears in two phases: (1) a gradual rise from 3.53 to 3.55-3.56 through midday (likely propagation of April 2 upstream pulse), and (2) a slight uptick at end of day (3.55→3.57 ft from ~22:00-22:45) that could be the very first signal from today's Harriet zone rain (0.42" average). Gauge recorded 0.12" local precip.
Richland Creek (07055875): Declined from 0.97-0.99 ft (residual from April 2 response) to 0.95 ft through the day. Then a clear rise began ~19:00 from 0.96 to 0.99 ft by 22:15 (+0.03-0.04 ft). This is the beginning of response to today's 0.62" Richland zone rain (peak HUC12s: Headwaters RC 0.656", Falling Water 0.585"). Rain peaked around 22:00-23:00 CDT, so this is the very early leading edge. More response expected on Day 35.
Bear Creek (07056515): Flat at 2.27-2.28 ft / 4.19-4.59 cfs through most of the day. Then at ~21:45 a clear rise began: 2.28→2.31 ft, discharge 4.59→6.02 cfs (+31%) by 22:30. This is the first detected response at Bear Creek above the noise floor in the entire study! The 0.67" zone average rain (peaking 0.709" in Headwaters Bear Creek at 0.391"/hr) is producing a detectable response despite still-dry antecedent conditions.
Bear Creek — FIRST DETECTION EVENT (high significance): - Precipitation: 0.671" zone average (0.709" peak HUC12), peak intensity 0.391"/hr - Antecedent: 7-day precip 0.26-0.35" (mostly from April 2 trace; still very dry) - Response: +0.03 ft / +1.4 cfs (from 4.59 to 6.02) — only the beginning; rain is still falling - Lag: Rain peaked ~22:00-23:00 CDT, gauge response began ~21:45 CDT — near-simultaneous, suggesting initial direct runoff reaching the gauge as rain is still falling - This is the first time Bear Creek has exceeded its noise floor (±0.01 ft) during the study. Previous non-detections: 0.10", 0.31", 0.52", 0.10", and 0.10". Today's 0.67" is the first exceedance of the ~0.6-0.8" dry-antecedent detection threshold hypothesized for Bear Creek. This confirms the threshold is approximately 0.6-0.7" on dry antecedent for Bear Creek. Confidence elevated to High.
Richland Creek — Continued calibration: - Precipitation: 0.621" zone average (0.656" peak HUC12 at 0.336"/hr) - Antecedent: 7-day 0.32-0.55" (slightly improved from April 2 rain; moderately dry) - Response: +0.04 ft (0.95→0.99) at end of day, beginning only - This is the second consecutive day Richland has responded. Yesterday's April 2 rain (0.29" zone average) produced +0.09 ft. Today's rain is more than double the input — response should be substantially larger on Day 35.
Boxley — Continued response from April 2: - The +0.12 ft total rise (1.76→1.88 ft) from 0.52" on extreme dry antecedent took ~36 hours to reach peak - This confirms the very slow response time at Boxley on dry antecedent, consistent with local knowledge about pool-filling. Compare to Event 1 (wet antecedent): 1.04" → +0.87 ft rise in ~4-6 hours. - Ratio: 0.52" → 0.12 ft = 0.23 ft/inch on extreme dry. Event 1: 1.04" → 0.87 ft = 0.84 ft/inch on wet. ~3.6x amplification from antecedent moisture at Boxley.
The April 2 Boxley rain pulse is propagating downstream: - Boxley began rising ~09:30 CDT April 2, peaked ~10:45 CDT April 3 (~25 hours of gradual rise) - Ponca began showing slight uptick at ~01:30 CDT April 3, more clearly by ~09:30 — roughly 12-24 hours after Boxley began rising - Pruitt: No clear signal yet, but late-day firming could be early arrival
This is consistent with low-flow propagation velocities, but the signal is so diffuse (spread over 24+ hours of gradual rise) that precise lag timing is difficult to establish. The extreme dry conditions and pool-filling behavior create a much more attenuated, slower-arriving pulse than we've seen in previous events.
April 2-3 compound sequence: The watershed is experiencing a two-pulse pattern: - Pulse 1 (April 2): Upper-watershed focused (Boxley 0.52", Ponca 0.33"), still propagating downstream through Day 34 - Pulse 2 (April 3, late): Lower/southeastern watershed focused (Bear Creek 0.67", Richland 0.62", Harriet 0.42"), response just beginning at end of Day 34
These two pulses will arrive at St. Joe and Harriet from different directions at different times — the upper mainstem pulse from upstream propagation, and the tributary/lower-watershed pulse from direct runoff into St. Joe tributaries and Bear Creek. Day 35 analysis should watch for whether these create a compound rise at St. Joe and Harriet.
Bear Creek first detection is the major finding. The threshold of ~0.67" on relatively dry antecedent (7-day ~0.3") producing the first-ever detectable response at this gauge during the study is a key calibration point. The response is small but unambiguous (+0.03 ft, +1.4 cfs above consistent baseline).
Harriet rising while St. Joe is declining in the afternoon is notable. Harriet went from 3.53 to 3.57 ft while St. Joe dipped to study-low 3.38 ft. This suggests Harriet is receiving direct runoff from its local HUC12s (Harriet zone 0.42" average) and possibly early Bear Creek contributions, independent of mainstem propagation from upstream. This is an excellent signal separation opportunity — any rise at Harriet today comes from Harriet-zone direct rainfall and Bear Creek, not from upstream mainstem, since St. Joe is at its lowest.