OUTLIERS: THE DRIVERS OF MY 40 YEARS OF BASIC RESEARCH IN HYDROGEOLOGY

Advances in the hydrogeologic sciences stem from meeting societal needs (e.g. aquifer testing, contaminant characterization); satisfying human curiosity about flow systems (e.g. mathematical and geochemical tools); and finally, understanding outliers— rare observations that make little sense with accepted theory. Outliers largely formed the basis of my own career.

The following outliers come to mind: electron microscopic images showing quartz dissolves at neutral pH ¹; chemistry showing groundwater flushing thick peat ²; over-pressured methane in deep peat ³; and isotopic measurements showing glacial meltwater in deep confined aquifers ⁴. These outliers led to multiple rejections for publication and then after publication, decades of exploration of implications of the resulting paradigm shifts. In this talk, I provide “back story” about these outliers that led me to the conclusion: “If reviewers give you “over-the-top” negative rejections for a submitted paper, rejoice! It probably means you are onto something important”.

What about the future of hydrogeology? I think climate disruption will drive our field’s research at all levels and that those young scientists who explore outliers, be they extreme events or unusual geochemical fingerprints, will have the best chance to make significant discoveries. In contrast, remain unsure if exploring “big data” with statistical and GIS tools that masks outliers will advance understanding beyond providing information at very large spatial frames of reference (big areas).

1. Bennett, P. and Siegel, D.I., 1987, Enhanced dissolution of quartz by dissolved organic carbon, Nature, vol. 326, p. 684‑686.
2. Siegel, D.I., and Glaser, P.H., 1987, Groundwater flow in a spring‑fen, raised‑bog complex, Lost River Peatland, Northern Minnesota, Journal of Ecology, vol. 75, p. 743‑754.
3. Romanowicz, E., Siegel, D.I., and Glaser, P.H., 1993, Hydraulic reversals and episodic methane emissions during drought cycles in mires, Geology, vol. 21, p. 231-234.
4. Siegel, D.I. and Mandle, R.J., 1984, Isotopic evidence for glacial meltwater recharge to the Cambrian‑Ordovician aquifer, north‑central United States, Quaternary Research, vol. 22, p. 328‑335.