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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
47 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.
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 dividing 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 is highly abundant in the environment and low-dose exposure is common. According to the Agency
for Toxic Substances and Disease Registry (ATSDR) toxicological profile,
oral exposure aluminum is generally not harmful. However, overexposure to aluminum is associated with Alzheimer's disease. People with certain kidney
diseases may be prone to retaining excess aluminum in their body.
Regulation: The USEPA defines a secondary MCL of 0.05 to 0.2 mg/L for aluminum
primarily because of taste, smell, and color associated with aluminum in drinking water.
The Navajo Nation sets an agricultural water supply standard for acid-soluble aluminum of
20,000 μg/L. The USEPA also defines a recreational screening level (RSL) for scenarios
where a hiker or camper may come in contact with increased levels of aluminum in soil,
sediment, or surface water of 170,000 μg/L.
Arsenic is a common metalloid in the environment. Inorganic arsenic is often colocated with mining activities, specifically coal and gold,
but also with uranium extraction and processing. People may often come into contact with different forms
of arsenic through the air they inhale, the food they eat, and the water that they drink. Some areas have
higher levels of naturally occurring arsenic that may infiltrate groundwater and surface water supplies.
Arsenic is listed in the Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile as a carcinogen
that is implicated in numerous adverse health outcomes and even death in high doses.
Regulation: Both the Navajo EPA and the USEPA set an MCL for arsenic in drinking water at 10 μg/L.
The EPA camper/recreational RSL is 50 μg/L. The Navajo Nation sets the limit for arsenic concentration
in agricultural water supplies at 2000 μg/L and at 200 μg/L for livestock watering.
Barium is most often found underground as naturally occurring ore deposits. It does not dissolve well in water,
meaning that concentrations in drinking water supplies are usually low. However, some barium compounds, such as barium acetate,
barium chloride, barium hydroxide, barium nitrate, and barium sulfide, do dissolve more easily but are not often found
in natural formations. Because it is commonly used in oil and natural gas production some local water supplies
may become contaminated. According to the Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile, barium is implicated in changes in heart rhythm and paralysis as well as other adverse health outcomes.
Exposure to barium in large doses may lead to death.
Regulation: Both the Navajo EPA and USEPA set an MCL for barium in drinking water at 2 mg/L. The
EPA camper/recreational RSL is 33 mg/L. The Navajo Nation does not define a limit for barium concentration
in either agricultural water supplies or for livestock watering.
Cadmium is an environmental metal most often associated with zinc, lead, and copper ore. It is also commonly found in batteries
and can be introduced into the environment via industrial discharge and waste disposal. According to the Agency for Toxic Substances
and Disease Registry (ATSDR) toxicological profile cadmium is
associated with kidney disease and damage to lungs and the nasal cavity.
Regulation: Both the Navajo EPA and USEPA set an MCL for cadmium in drinking water at 5 μg/L. The EPA
camper/recreational RSL is 83 μg/L. The Navajo Nation sets the limit for cadmium in both agricultural and livestock water supplies at 50 μg/L.
Copper is an abundant chemical element in the earth's crust associated with mining and corrosion of household water pipes. It is an essential nutrient found
in many food sources. However, according to the Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile, excess buildup of copper in humans is associated with Wilson's disease, Indian childhood cirrhosis, and other disorders of the liver.
Regulation: Neither the Navajo EPA nor the USEPA set an MCL for copper, but define an MCL goal of 1.3 mg/L. The EPA camper/recreational RSL is 67 mg/L.
The Navajo Nation sets the limit for copper in agricultural water at 200 μg/L and at 500 μg/L for livestock water supplies.
Iron is a highly abundant element in the earth's crust and is also an essential trace element for the health and functioning of living organisms. According to the
World Health Organization
humans typically require anywhere from 10 to 50 mg of iron every day. Iron is ubiquitous in water supplies worldwide. Excess iron in water often comes from deterioration
of household plumbing systems, leading to discoloration and metallic taste.
Regulation: Both the Navajo EPA and the USEPA set a secondary MCL for iron of 0.3 mg/L. The EPA camper/recreational RSL is 120,000 μg/L. There are no
limits for iron in agricultural or livestock water supplies.
Manganese is a trace element found in some rocks and soil and is used mainly in steel production to improve hardness. The primary source of exposure to manganese
is through food, and it is ubiquitous in nearly all water supplies. Low manganese levels in drinking water can affect its taste and color. According to the Agency
for Toxic Substances and Disease Registry (ATSDR) toxicological profile, manganese
is an essential nutrient, though because it mainly resides in the brain, some neurological system disturbances may occur with particular adverse effects on fetuses.
Regulation: The USEPA defines a secondary MCL for manganese in drinking water at 50 μg/L. The EPA camper/recreational RSL is 7800 μg/L. The
Navajo Nation doesn't limit concentrations of manganese in either agricultural or livestock water supplies.
Lead is a highly toxic metal distributed in ore deposits across the world. It is associated with various ore smelting and improper waste disposal that
may infiltrate local water supplies. Historically, lead was used in many consumer products, including gasoline, paint, and household plumbing. Many older
plumbing systems still contain lead pipes or soldered joints. According to the Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile, lead toxicity has adverse effects on every organ
because lead is easily distributed throughout the entire body. Specifically, "neurological, renal, cardiovascular, hematological, immunological,
reproductive, and developmental effects" are pronounced, with most concern on early neurological development.
Regulation: The USEPA sets the MCL for lead in drinking water at 0, while the Navajo EPA sets it at 15 μg/L. The EPA camper/recreational
RSL is 200 μg/L. The Navajo Nation limit for lead in agricultural water is 10,000 μg/L, and 100 μg/Lfor livestock water.
Selenium is a naturally occurring element that is concentrated in certain pockets of the earth's crust in some rocks and soil. It's also often produced
as a byproduct in copper refining. It often binds with other metals, like copper, lead, and nickel. Because of its ubiquity in many commercial products
like plastics, paints, and some shampoos, it's introduced into water supplies through waste disposal. According to the Agency for Toxic Substances and
Disease Registry (ATSDR) toxicological profile, selenium is an essential
nutrient, though excess exposure to selenium may be associated with brittleness of the hair or nails, and though uncommon in the United States, chronic
overexposure may lead to death.
Regulation: Both the Navajo EPA and the USEPA set the MCL for selenium in drinking water at 0.05 mg/L. The EPA camper/recreational RSL is
830 μg/L. The Navajo Nation limit for selenium in agricultural water is 20 μg/L, and 50 μg/L for livestock water.
Uranium is a naturally occurring radioactive element found in deposits across the earth's crust. Today, enriched uranium is mainly used as fuel for nuclear
power generation. It is distributed throughout the environment primarily through wind and water movement. It can be taken up into plants through root systems.
Abandoned uranium mines (AUMs) across the Navajo Nation may be inadequately reclaimed, increasing the likelihood of uranium mobility through the environment.
Drinking water is the primary source of uranium exposure. According to the Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile, uranium exhibits significant adverse effects on kidneys.
Animal studies show uranium residence in other organs, such as brain tissue. Some uranium compounds may cause skin irritation.
Regulation: Both the Navajo EPA and USEPA set the MCL for uranium in drinking water at 30 μg/L. The EPA camper/recreational RSL is E-04 mg/kg-day,
based on the ATSDR Minimal Risk Level (MRL) for exposure to uranium soluble salts. There is currently no numeric standard limit for uranium in either
agricultural or livestock water supplies.
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 2.0 and
do not necessarily reflect those of the agencies.