WHY IS THE INFLUENCE OF GROUNDWATER/VADOSE-ZONE RESEARCH IN THE HYDROLOGIC SCIENCES DECLINING? (Invited Presentation)

This study uses online, digital data-bases of articles, text mining and machine learning to examine trends in research in hydrogeology and hydrological sciences. The focus here is to determine where research is heading and what the drivers are. Our analysis uses records (i.e, article titles, key words and abstracts) from Water Resources Research (WRR; 16,657 papers; 1965-2017) and Environmental Science and Technology (ES&T; 37,441 papers; 1967-2017). In these journals, subsurface hydrology (SH), including groundwater and vadose-zone topics, competes for space with other areas. The relative abundance of papers in SH through time as compared to other topics is taken as measure of SH market share. From 1960s to late 1970s, SH articles comprised ~10 to 24% of all articles in WRR and zero to ~3% in ES&T. From the 1980s through the middle to late 1990s, the relative market share for SH articles expanded significantly in both journals. The peak share of SH papers was 52.2% for WRR in 1995 and 11.3% for ES&T in 1998. Over the next two decades market share for SH in WRR and ES&T declined to 30% and 7%, respectively. For WRR, much of the growth in the SH share is explained by the growth in contaminant-related papers. For ES&T, nearly all the growth is from contaminant-related papers. The main driver appears to be economic, driven by the boom/bust cycle in contaminant hydrogeology. For many, the boom in contaminant hydrogeologyis relatively obscure and unappreciated. From 1975-2000, Americans were concerned that much of their groundwater was poisoned. The result was unprecedented infusions of cash for government and university research, and programs to clean up the worst industrial sites, military bases, DOE weapons facilities, refineries, and oil-fields and more. This rare confluence of fear, funding and timing let SH dominate the hydrological sciences and emerge as a player in environmental chemistry. With the bust, the decline in the SH share of WRR and ES&T followed the decaying product growth curve that we suggested 17 years ago – less money leading to less research. The boom in contaminant hydrogeology probably represented the 1000-year flood of money for SH. Nothing like this has ever happened before, nor is it likely to be repeated. Elvis has left the building; there are no more encores.