Five Years of Baseline Data, and What It Changed

When we installed the first Cedar Fork gauge in 2021, the going assumption among the watershed groups we worked with was that monthly grab sampling was "good enough" for trend detection. Five years of continuous fifteen-minute readings later, we don't think that's true anymore.

The clearest example: a slow, multi-year dissolved-oxygen decline at our Lower Gauge station that never once showed up as an outlier in any single monthly sample, because it moved by about 0.4 mg/L per year — well within the noise band of a monthly program, but unambiguous once you have a continuous baseline to regress against.

We're not arguing grab sampling is useless — lab-verified chemistry still matters for anything a probe can't measure directly. But for trend detection specifically, the five-year record changed our answer.