Low water and mercury violations converge downstream

July 13, 2026Michigan Lake Plain

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Stream flow has dropped to 60 cubic feet per second — a ninety-fold decline from the 460 cubic feet per second recorded just weeks ago. At such austere levels, the chemistry of the water shifts. Mercury, which lingers in sediment and driftwood, begins to methylate: bacteria convert it into an organic form that fish absorb readily, concentrating as it moves up the food chain to herons and other predators.

During this vulnerable season, the treatment plant has exceeded its mercury permit limit for four consecutive quarters, with nineteen percent over the threshold in the most recent month alone. The prior three quarters show a troubling pattern: exceedances of 16, 27, and 38 percent. Nearby stream reaches are federally listed as impaired — a designation that reflects precisely this kind of cumulative stress, where low flow amplifies the toxicity of discharges that might be manageable at higher water levels.

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