Prioritizing water availability study settings to address geogenic contaminants and related societal factors

Abstract

Water availability for human and ecological uses depends on both water quantity and water quality. The U.S. Geological Survey (USGS) is developing strategies for prioritizing regional-scale and watershed basin-scale studies of water availability across the nation. Previous USGS ranking processes for basin-scale studies incorporated primarily water quantity factors but are now considering additional water quality factors. This study presents a ranking based on the potential impacts of geogenic constituents on water quality and consideration of societal factors related to water quality. High-concentration geogenic constituents, including trace elements and radionuclides, are among the most prevalent contaminants limiting water availability in the USA and globally. Geogenic constituents commonly occur in groundwater because of subsurface water-rock interactions, and their distributions are controlled by complex geochemical processes. Geogenic constituent mobility can also be affected by human activities (e.g., mining, energy production, irrigation, and pumping). Societal factors and relations to drinking water sources and water quality information are often overlooked when evaluating research priorities. Sociodemographic characteristics, data gaps resulting from historical data-collection disparities, and infrastructure condition/age are examples of factors to consider regarding environmental justice. This paper presents approaches for ranking and prioritizing potential basin-scale study areas across the contiguous USA by considering a suite of conventional physical and geochemical variables related to geogenic constituents, with and without considering variables related to societal factors. Simultaneous consideration of societal and conventional factors could provide decision makers with more diverse, interdisciplinary tools to increase equity and reduce bias in prioritizing focused research areas and future water availability studies.

Keywords: Arsenic; Environmental justice; Federal research; Geogenic contaminants; Groundwater; Hydrology.

Fig. 1

Hydrologic regions (black boundary lines), candidate watershed basins (blue boundary lines), and selected principal aquifers by lithology (shaded areas). a Eighteen hydrologic regions and 163 candidate basins (Van Metre et al., 2020); and b hydrologic regions and selected principal aquifers by lithology (Miller, 1999)

Fig. 2

Conceptual model that considers natural conditions, human stressors, and societal factors relevant to understanding and prioritizing geogenic-focused water quality research

Fig. 3

Illustration of the study basin ranking process for two representative variables: row 1 is a prediction of elevated arsenic in groundwater, and row 2 is likely the presence of brackish groundwater at a depth shallower than 500 ft (152 m). For each variable row, panel (a) shows the original national data set used for the variable; panel (b) shows the variable value assigned to each candidate basin; panel (c) shows the national percentile rank of each basin according to the single variable, with darker colors depicting higher percentile rank. Graphical presentations for all 12 variables are presented in supplemental Figure S2. All variables are described in Table 3 and in a data release (Qi et al., 2023)

Fig. 4

Maps of national percentile ranks of all variables for all candidate basins with darker colors depicting higher percentile rank. (a) panels, system condition or stress variables; (b) panels, human alteration variables; (c) panels, historical disparity variables. Variable descriptions are presented in Table 3

Fig. 5

Percentile ranks of variable data, by region. Wider gray shading illustrates a higher proportion of the region’s data. Purple triangles indicate candidate basins with the highest national rank (Fig. 6a and Figure S3)

Fig. 6

Maps of national candidate basin ranking with and without the historic disparity variable category, with darker colors indicating higher rank (higher priority). a National ranking that includes the novel historical disparity category of variables. b National ranking using only the conventional human alteration and system condition or stress categories of variables. Some basins in the northeast, eastern coast, and central southwest have elevated priority (1 being the highest rank and highest priority) with the inclusion of historic disparity variables. Detailed basin variable percentile ranks are provided in Figs. 4 and 5 and Table S4