Dissolved oxygen hits new low as thermal stress peaks

July 11, 2026Flat to Rolling Plains

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Dissolved oxygen dropped to 3.6 mg/L today—the lowest reading yet this month, sliding further below the already worrying 3.9 recorded just five days ago. A sudden flow pulse brought 35 cubic feet per second through the creek, a seven-fold spike from the sluggish 5-foot-per-second average that has prevailed for two weeks. But the pulse arrived far too late: midsummer thermal loading has run so deep that one surge of cooler water cannot reverse it.

(Callibaetis spp.) have been holding steady throughout the area all month—sightings from late June into early July across the lower reaches. These mayflies thrive in moderate flow and good oxygenation; their presence here now underscores what these collapsing conditions are working against. Water temperature climbed to 20.6°C, and while pH remains neutral at 7.5, the oxygen deficit alone threatens the cold-water invertebrate community that has persisted through drought and low flow.

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