Dissolved oxygen plummets toward critical fish-kill threshold

July 19, 2026Cross Timbers Transition

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Dissolved oxygen has dropped to 2.8 mg/L — the lowest reading in six weeks of mounting hypoxia, and barely above the threshold where fish kills accelerate. At tonight's water temperature of 26°C, a single calm night with no wind mixing could push the stream over that edge. The window to recovery is closing fast.

Midwest City's North wastewater treatment plant is currently in permit noncompliance, adding a steady nutrient load to a system that has lost its margin for error. This stretch of stream — typical of the grassland-woodland transition here — has little riparian buffer and no significant flow reserve to dilute or flush the excess. What remains is a narrow, precarious balance between biological demand and the oxygen the water can hold.

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