Navajo WaterGIS 2.1
Navajo WaterGIS 2.1:
Launch The Web Map

What is Navajo WaterGIS 2.1?

This interactive web map gives you access to the most complete spatial database of unregulated water sources on and around the Navajo Nation. Each of the 4,824 water source records in this app contains data for up to 49 water quality parameters, including radionuclides, metals, and other regulated contaminants.

We also assess each water source for its suitability for particular activities with water from these sources, indicating whether the water can be used for irrigation (like watering home gardens), household chores (like washing laundry and dishes), livestock watering, or if the water should be avoided completely.

We do not recommend drinking any water from these sources. However, we recognize that each water source in this map is used for many daily activities.

Each determination of suitable use comes with an easy-to-read metric of our confidence in it, which we base on a number of factors, like how many water samples were taken, how old those samples are, and if we had to use statistical approaches to estimate concentrations of contaminants in the source.

Access the site here or by clicking on the link at the top of the page or keep reading for more background information.

Who is this site for?

Anyone can use this site. However, because many Navajo residents may lack access to a computer or the internet, and because there is a substantial degree of technical information in the site that may necessitate deeper conversations between experts and community members, the aim of Navajo WaterGIS is to support those conversations. The target audience of Navajo WaterGIS is people who regularly interface with Navajo community members.

What does this site show you?

Navajo WaterGIS displays the locations and all available water quality parameters of unregulated water sources on and around the Navajo Nation. It also provides information about potential suitable uses of water from these sources, including household chores, watering gardens, and watering livestock.

Background

In the United States, the use of unregulated water sources – defined as sources that do not meet criteria to be classified as a public water system as defined by the Safe Drinking Water Act - are used regularly for livestock watering, agriculture, domestic, and other purposes. Nationally, more than 45 million people rely on unregulated water sources for drinking water; however, there remains infrastructure disparities for drinking water access in communities on Tribal nations. For the Navajo Nation, a sovereign Indigenous nation in the Southwestern United States, between 7% and 30% of homes lack plumbing to deliver household drinking water, so residents are compelled to access other water sources – regulated and unregulated alike. Previous unregulated water quality studies on the Navajo Nation were regionally focused and unsuitable for evaluating water quality trends across the Navajo Nation, an area that encompasses more than 71,000 square kilometers in Arizona, New Mexico, and Utah. Therefore, beginning in 2011 the Community Environmental Health Program at the University of New Mexico began to compile existing water quality datasets, principally for unregulated groundwater sources, in a single geospatial relational database.


Researchers at the University of New Mexico Center for Native Environmental Health Equity Research, the New Mexico METALS Superfund Research Program, University of Arizona, Northern Arizona University, and the Southwest Research and Information Center have compiled a database of water quality measurements from groundwater wells on the Navajo Nation using data from the U.S. Geological Survey, U.S. Army Corps of Engineers, U.S. Centers for Disease Control and Prevention, Navajo Nation Environmental Protection Agency, and data from researchers at the University of New Mexico, Diné College and Northern Arizona University. To date, this data compilation has been used for publications but has not been disseminated publicly. The purpose of this website is to facilitate access to these compiled water quality data. The application design enables users to view water quality information using statistical and geospatial tools. Our hope is that this information will support individual and community decisions about water use from unregulated sources.

The Data

The compiled dataset consists of two primary data tables and can be downloaded from the Environmental Data Initiative (EDI) Portal. The first table is derived from the Navajo Nation Wells Database, consisting of more than 5,000 groundwater well records. The second table includes water quality data from 18 distinct studies collected between 1905 and 2020. The data table includes 845 analytes with the largest number of observations for trace metals, metalloids, radionuclides, and water chemistry parameters. The data presented here represent the publicly available portion of the data compilation. This tool should not be interpreted as a definitive or complete record of all wells and water quality results in the region. In total, the dataset presented here visualized results for 4,824 water sources.

Some studies recorded uranium concentrations in units of activity (picocuries per liter), which were converted to mass per unit volume (μg/L) by multiplying activity by 0.67. If multiple measurements were available per analyte per well, the maximum concentration was determined for radionuclides, metals, and metalloids, and the median concentration was calculated for pH, conductivity, hardness, and other measures of water chemistry. Measurements that are below the instrument limit of detection are recorded in the dataset. Values are imputed as the LOD for visualization purposes. The downloadable dataset records the LOD and may be used with various imputation methods for more rigorous statistical analysis.

Suitable Uses

Even though we can't recommend drinking water from the unregulated sources depicted in this map, we recognize that they may serve other uses for local residents. Here, we evaluate water quality at each source against regulatory guidelines to determine the suitable use(s) of water from them, including household chores, such as cleaning dishes or laundry, small-scale irrigation, and livestock watering. These evaluations are not recommendations.

We relied on regulation from the USEPA and the Navajo Nation EPA when developing our assessments. Specifically, the Navajo Nation Agricultural Water Supply and Livestock Watering standards, the USEPA Recreational/camper Regional Screening Levels (RSLs), as well as primary and secondary maximum contaminant levels (MCLs) for drinking water defined by either the USEPA or Navajo Nation EPA if the regulatory limit is different.

Our assessments are based on the presence of ten chemical contaminants in each water source (click on each to expand):

Aluminum (click to expand)

Arsenic (click to expand)

Barium (click to expand)

Cadmium (click to expand)

Copper (click to expand)

Iron (click to expand)

Manganese (click to expand)

Lead (click to expand)

Selenium (click to expand)

Uranium (click to expand)

The Assessment Model:

For each of the ten chemicals we define degrees of safe concentrations based on the guidelines and regulations discussed above. Then, we utilized a machine learning model, adaptive fuzzy neural inference system (ANFIS), to define and parameterize more than 1.3 million rules based on every possible combination of high, medium high, medium low, and low concentrations of each chemical in each water source.

We use this approach for two main reasons. First, elevated mixtures of multiple regulated contaminants that don't necessarily exceed regulatory limits may still present acute or long-term health hazards that need to be assessed together, rather than one contaminant at a time. Second, water quality changes over time, so we can never be completely certain what the water quality is at an exact moment. This approach lets us handle that uncertainty while still making meaningful inference.

Household use:

Household water uses may typically include cleaning (such as dishes or laundry) or sanitation, but not any human consumption. As such, concentrations of regulated contaminants may be higher than maximum concentration levels (MCLs) defined by either the Navajo EPA or USEPA. Because dermal exposure to potentially contaminated waters is possible with household use, we rely on the EPA recreational/camper regional screening levels (RSL) to make our assessments.

Irrigation:

Hauled water may be used to irrigate small gardens or other food sources for consumption. Our assessments for irrigation water are based on the Navajo Nation agricultural water supply limits, which you can see here.

Livestock watering:

Many of the water sources included in this resource are livestock wells, though without complete records we can't adequately determine the exact number of livestock-specific wells, nor can we be sure that multi-purpose wells aren't also used for livestock water. We base our assessments for livestock watering on the Navajo Nation livestock watering guidelines, which you can see here.

Avoid:

We recommend avoiding any water sources with concentrations of Al, As, Ba, Cd, Cu, Fe, Mn, Pb, Se, and U higher than those defined in the guidelines discussed above. Furthermore, we individually assessed water sources with measurements of radioactive elements like Radium-226 and 228 or gross alpha particles and excluded any sources with at least one measurement higher than federally stipulated limits (e.g., total radium greater than 5pCi/L).

Confidence

In instances where no laboratory-based measurements of these chemicals are available, we interpolated their levels using spatial co-kriging between known water samples, depth-to-water measurements, and soil/sediment samples. We define our level of confidence in our assessments according to three parameters: the accuracy of our estimates if we made one, the number of laboratory samples collected, and how recently samples were collected. When we estimated concentrations of chemicals in water, we also calculated the standard errors of our estimates. Laboratory-based observations have an estimation standard error of 0 – otherwise the higher the error the lower our confidence. Similarly, if only one laboratory sample for a given chemical in a water source exists, we are less confident that it accurately represents water quality in that source than if there are multiple samples collected and analyzed. Finally, because both water quality and laboratory methods change over time, we are less confident in samples collected and analyzed from more than ten years ago. Simply put, our confidence is highest for sources where multiple samples were collected within the last decade, and our confidence erodes when we have less observational data.

This work is supported by the New Mexico Integrative Science Program Incorporating Research in Environmental Sciences (NM-INSPIRES) Center at the University of New Mexico (1P30ES032755); Agnese Nelms Haury Program in Environment and Social Justice at the University of Arizona. Additional funding for the projects that contributed to the water sample collection and analysis includes the National Institute for Environmental Health Sciences (RO1ES014565, R25ES013208, P30ES012072); a NIGMS ASERT IRACDA postdoctoral fellowship (K12 GM088021); the UNM Center for Native Environmental Health Equity Research -- A Center of Excellence In Environmental Health Disparities Research (1P50ES026102 & USEPA #83615701); University of New Mexico METALS Superfund Research Program (1P42ES025589); and the Navajo Birth Cohort Study (U01 TS000135-05, NBCS/ECHO 1UG3OD023344).

The material presented here has not been formally reviewed by the funding agencies. The views expressed are solely those of the authors of Navajo WaterGIS and do not necessarily reflect those of the agencies.