DON SIEGEL’S EARLY YEARS AS A GROUNDWATER-FLOW MODELER

Many geochemists and hydrogeologists know of Don Siegel’s contributions to wetland science, isotope geochemistry, and contaminant hydrogeology, and his pursuits of the more provocative aspects of these disciplines and their applications. However, few are aware of Don’s early contributions to groundwater-flow modeling. His collaborations with colleagues from the University of Minnesota and USGS during the late 1970s and early 1980s provided the foundation for highly successful and influential site-specific long-term research. Don, along with Tom Winter from the USGS, initiated a study to investigate the influence of groundwater on water and chemical budgets of Williams Lake in northern Minnesota. Don used an early version of what later would become MODFLOW to simulate exchange between groundwater and the lake. One of the recommendations in a 1980 Siegel and Winter USGS report was to further investigate transient water-table mounds and local-scale geology. This early work led to long-term watershed-scale research that to date has produced 126 peer-reviewed papers and journal articles. Concurrently, Don collaborated with Paul Glaser, Herb Wright, Olaf Pfannkuch, and others from the University of Minnesota to study the hydrology, geochemistry, and ecology of the largest peatland in the US outside of Alaska. Don simulated groundwater flow along an 80-km transect that traversed the Red Lake Peatlands. In a USGS report published in 1981 and a paper published in Journal of Ecology in 1983, Don showed groundwater mounds forming beneath raised bogs that drove flow of water and solutes to adjacent fens. The resulting hypothesis that local and regional-scale groundwater flow could be responsible for the distribution of bogs and fens within this peatland was the beginning of extensive collaboration with Paul Glaser and others that led to long-term investigation of the ecology and biogeochemistry of large boreal peat basins from Minnesota to the Hudson Bay Lowlands, including research that demonstrated the close linkage of climate, groundwater and carbon dynamics within these ecosystems. Don's seminal work on groundwater interactions with lakes and peatlands has inspired others to expand their horizons beyond the narrow confines of their disciplines and seek close collaborations with experts in other fields of study.