About the Data

Uranium mining in Navajo Nation, Impacts on Environment and Health, and Geospatial Modeling

Background

Residents of Navajo Nation (Dine Bikeyah), a sovereign Indigenous Tribal nation of the American Southwest, are vulnerable to environmental pollution from various sources such as resource extraction and unregulated solid waste disposal (Kirkemeno et al. 1998; Ong et al. 2014; Lewis et al. 2017). From the 1940s through the 1980s, one of the most sought-after resources was uranium, and today there are hundreds of abandoned uranium mines across Navajo lands. This legacy of mining and the continuing presence of AUMs has caused significant environmental contamination in Navajo Nation (Eichstaedt 1994; Masco 2013; Voyles 2015; Lewis et al. 2017). Understanding the distribution of potential exposure to these AUMs is a significant concern in Navajo communities. Some recent work to model this exposure potential includes a multi-criteria decision analysis (MCDA) (Malczewski 2006) model, developed by Lin et al. (2020) to analyze and understand potential exposure within Navajo Nation.

MCDA Model

The MCDA model predicts potential exposure based on several environmental criteria (wind, topography, hydrology, etc.) represented as raster surfaces, in which cells contain an index value indicating this potentiality on a normalized scale of 0-1. The final model output is a weighted linear combination (WLC) of the individual criteria. This final output represents cumulative potential for exposure from the above-described environmental criteria (Lin et al. 2020).

Methodology

Critical layers were created following the methodology by Lin et al. (2020). Critical layers were generated using the following data-sources: abandoned uranium mine point data sourced from the U.S. Environmental Protection Agency (USEPA) (U.S. EPA 2007) ; meteorological data sourced from the North American Regional Reanalysis (NARR) model (NOAA 2020) ; a 30-m digital elevation model (DEM) sourced from the U.S. Geological Survey (USGS) (U.S. Geological Survey n.d.) ; road networks sourced from the U.S. Census Bureau (U.S. Census Bureau n.d.) ; downslope drainage and ground water sample data sourced from USEPA and the University of New Mexico (U.S. EPA 2007; Hoover et al. 2017) (U.S. EPA 2007; Hoover et al. 2017); and vegetation data from the NASA Vegetation Index and Phenology (VIP) global dataset (Didan 2010). The critical layers (represented as raster datasets) are as follows:

• Proximity to AUM sites

• Proximity to roads

• Proximity to downslope drainages from AUM sites

• Topographic landforms

• Wind index

• Topographic Wind Exposure (TWE)

• Vegetation Robustness (NDVI)

• Groundwater contamination

This map displays an interactive version of the combined predicted exposure, including mine locations. Users can pan and zoom to a specifc location, such as their home and see the predicted exposure class for that area by clicking on the map.

The main aim of our web map was to display the described MCDA model output and make it interactive. In which a user can both visually pan and zoom on the predicted exposure surface and retrieve the predicted exposure value for a given area. Such interactivity will hopefuly it easier for a resident of Navajo Nation to, for example, know the predicted potential exposure from this model at their home’s location, or other areas of interest.