The State of EPA Tribal Drinking Water Data

Tribal Drinking Water Data Landscape–EPA Data Systems

This section first introduces the drinking water data systems and exploration tools maintained by EPA–SDWIS and ECHO–and discusses how Tribal drinking water data is represented and inclusion in these systems, based on EPIC’s evaluation.

  • The Safe Drinking Water Information System (SDWIS) is maintained by EPA for the implementation of the Safe Drinking Water Act (SDWA). EPA makes SDWIS data available to the public through several interactive dashboards and combines it with other federal datasets for further analysis (see here). SDWIS is the only national, convenient, publicly accessible water quality dataset that includes data from Tribal water systems. 

    Utilities, “whether operated privately, by Tribes, or by the federal government,” conduct their own testing and report the results to the primacy agency. These agencies “collect detailed system and monitoring data from systems within their jurisdictions, and submit a portion of that data quarterly to EPA” via SDWIS. Required reporting includes:

    • System information (e.g., name, type—community, transient, non-transient—population served, and source water type)

    • SDWA violations

    • Enforcement actions taken to return systems to compliance 

    EPA is the primacy agency for all PWS in Indian Country, with the exception of Navajo Nation, which is the only Tribe with SDWA primacy. 

    Indian country is defined by statute at 18 U.S.C. 1151 to include all lands within Indian reservations, dependent Indian communities, and allotted lands,” and the EPA provides a useful webpage that describes how they implement this definition in their environmental regulatory programs. Primacy status (whether EPA, the Tribe, or state have primacy) does not affect Indian country designation.

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  • The Enforcement and Compliance History Online (ECHO) database makes SDWIS data publicly available alongside other EPA regulatory datasets. ECHO compiles environmental regulation data from multiple data systems and is a user-friendly tool to understand facility compliance and enforcement, investigate pollution sources, analyze data trends, and create maps. Safe Drinking Water Information System (SDWIS) is just one of the environmental regulation datasets included on ECHO.

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  • The ECHO Facility Search allows users to access detailed monitoring and compliance histories for individual water systems. Users can search by PWSID, system name, or apply filters (e.g., location, system type). Each Facility Report includes monitoring and compliance history pulled from SDWIS and other relevant environmental regulatory data systems (if a facility is subject to those environmental regulations). The ECHO Facility Report also links Census demographic data to the facility, displaying demographic statistics for the population located within a few miles of the facility address.

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  • The ECHO Drinking Water Dashboard enables users to filter ECHO drinking water data by primacy agency type, EPA Region, state/territory, Tribe name, water system type, system size or source water. Users can generate dashboards that display violations, enforcement actions, and compliance statistics over time. This tool supports comparisons between Tribal and non-Tribal systems nationwide and is particularly useful for visualizing disparities or trends in Indian Country.

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Discussion of Tribal Drinking Water in EPA SDWIS Data

  • In July 2024, the EPA published the nation’s first comprehensive map of community water system service area boundaries. The service area boundaries for the over 44,000 community water systems were developed using a combination of “publicly available state datasets, data directly from water systems, and EPA-modeled service area boundaries,” and purports to include “all 50 states and Washington, DC as well as tribal systems.” 

    This dataset enables more precise demographic analysis of the populations served by individual systems, enhancing evaluations of drinking water equity. For any given system, the map shows the PWSID, the primacy agency, the number of people served, the number of service connections, and links to the system’s ECHO Facility Report. 

    By linking service area boundaries with detailed demographic and income data, users can analyze who is receiving safe or unsafe drinking water, estimate domestic well usage, project changes in water demand, conduct regionalization studies, and plan emergency response. EPA has developed a fact sheet on the dataset uses as well as a set of sample use cases.

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TLDR:

  • Tribal drinking water managers report limited access to EPA drinking water data relevant to Tribal lands–part of a broader pattern of barriers in accessing federally collected data about Tribes.

  • There are gaps between the reality of drinking water access and what is captured in EPA data, in large part because EPA data is captured for federal regulatory purposes. 

  • There are four different identifiers in EPA SDWIS data that researchers use to assess drinking water access Tribal lands: the Indian country indicator, EPA Area Type/Tribe Name, Tribe Name filter, and Native American owner type. The most commonly used filter to understand Tribal drinking water access is the Indian country indicator.

    • There are three EPA ECHO data dictionary definitions for the Indian country indicator.

    • Our spatial analysis, using SABs and SDWIS data, shows that the SDWIS Indian country indicator may exclude systems that serve some Tribal communities due to jurisdictional complexity or data entry errors.

    • SDWIS Native American owner type is missing a meaningful definition and may be inconsistently applied.

  • More robust data caveats and descriptions of data limitations for Tribal data specifically are needed for EPA’s drinking water datasets.

  • The SABs dataset likely inaccurately represents service boundaries for water systems on Tribal lands.

  • Data limitations common in EPA datasets are amplified for systems serving Tribal lands.

Challenges Reported by Tribal Drinking Water Managers

We acknowledge that EPA has made significant improvements to public access to drinking water data in recent years. Tribal water system managers we spoke with highlighted the usefulness of the drinking water dashboard, particularly the inclusion of Tribal systems in the dashboard. 

The data limitations we discuss below are shared in the spirit of collaboration, with the goal of collating known challenges in one place for the benefit of EPA staff and public data users. We recognize that EPA’s data collection methods are structured around compliance with the Safe Drinking Water Act and other federal mandates. However, the execution of these responsibilities is shaped by the complexities of federal Indian law—legal and jurisdictional structures that are not always well understood by all agency staff or external data users, and that are difficult to map directly onto drinking water data collection or analysis frameworks. 

Tribal systems are frequently left behind, in funding, resources, and in data resources. One former Tribal environmental director, who had previously managed a municipal water system, described the contrast clearly: in her municipal role, she could easily request and access data from EPA. But in her Tribal role, even identifying the right contact at EPA was difficult. Staff sometimes claimed the data wasn’t available, and it often took months—or never arrived

One might expect that EPA primacy would improve data quality and access for Tribal systems. Instead, she described the relationship as one in which Tribes felt "out of sight, out of mind." While we cannot fully explain this disconnect, it may reflect structural limitations within the agency: EPA is a federal institution built to respond to federal mandates, and even staff dedicated to Tribal affairs may lack the necessary resources to fully support Tribal data needs.

Given the constraints that Tribal drinking water operators face, it is especially important that EPA’s data tools are accurate, accessible, and useful. Many Tribal systems do not have dedicated data analysts or GIS staff—making intuitive and well-documented systems essential.

SDWIS: Usefulness and Limitations

Despite its regulatory intent, SDWIS is widely used by researchers and policymakers as a proxy for national drinking water quality and access.

Other researchers have described how SDWIS’s convenience–with “sets of independent and dependent variables–can be attractive to researchers. However, this can result in “data-driven research” where findings are shaped more by what’s available than by what’s meaningful, especially for Tribal contexts.

For Tribal drinking water data in particular SDWIS contains Tribal identifiers that can conveniently represent drinking water access among Tribal communities or on Tribal lands. However, each reflects EPA’s narrow regulatory lens. We found inconsistencies within and across datasets and a general lack of documentation specific to Tribal systems.

Our exploration of EPA’s data systems and conversations with Tribal drinking water operators and researchers found that there are a number of discrepancies between and within EPA datasets. We found that despite being very complex, the descriptions of Tribal data limitations are few, relevant terminology is not always adequately defined, and data systems are not designed to capture the realities of Tribal drinking water access.  We evaluated three identifiers in SDWIS data that can be used to get a picture of Tribal drinking water access, and discuss the limitations of each of these filters in-depth below. 

  • The Indian country indicator (via the ECHO Facility Search) and/or the EPA Area Type/Tribe Name indicators (via the SDWA data download, and/or the Tribe Name filter (in the Drinking Water Dashboard) can all be used to understand drinking water access on lands where Tribes exert their sovereign authority.

    • At this time, SDWIS’ Indian country indicator is the best proxy for understanding drinking water access on Tribal lands when using the SDWIS dataset. As we discuss below, data users should be aware that it doesn’t capture particular Tribal lands and communities with jurisdictional complexities, nor does it capture the demographics of the communities served by these drinking water systems. 

  • The Native American owner type (via the SDWA data download) has been used by researchers to proxy Tribal drinking water access.

  • Since 2024, the Service Area Boundaries (SABs) dataset could, theoretically, be linked with Tribal boundaries data, Census demographics, and SDWIS data to capture some picture of who has access to what water on and outside of Tribal lands. 

Below, we discuss the limitations of these datasets and filters that we identified in our evaluation.

Missing or incomplete definitions in EPA Tribal drinking water data.
Note that the terms below are all subject to EPA’s Tribal lands Data Caveat, which states that EPA makes no claims to accuracy of Tribal lands or boundaries data.

  • Different EPA ECHO data dictionaries and help pages include different definitions of the Indian country indicator (here, here, and here). In the ECHO Facility Search, a user can filter for water systems that are “in Indian country.” 

    1. The first, and most likely accurate, definition is provided in the ECHO EPA Detailed Facility Report Data Dictionary: “Indian Country: A value of "N/A" (Not Available) indicates this information is not maintained in the program data system. "N" indicates the facility is not in Indian country, and a value of "Y" indicates the facility is in Indian country according to EPA's Facility Registry Service. Indian country is defined by statute at 18 U.S.C. 1151 and includes all lands within Indian reservations, dependent Indian communities, and allotted lands.” 

  • The Native American owner category in SDWIS and associated tools is sometimes used by researchers to understand Tribal drinking water access or quality. However, our group could not locate a definition after searching the ECHO EPA Detailed Facility Report Data Dictionary or SDWIS Federal Reporting Services Filter Dictionary.

    1. We do not know who enters the category into SDWIS, or whether uniform guidance is provided to those individuals on how to select Native American owner. The category has been understood by some as ownership by Native American governments, but we found no evidence that this is the case. It is even more confusing when considered in the context of the existing ownership categories, which are as follows (and are identified, but not defined, in the SDWIS Federal Reporting Services Data Dictionary): 

      • F - Federal Government; L - Local Government; M - Public/Private; N - Native American; P - Private; S - State Government

    2. We spoke with other researchers who noted that the Native American owner category was one of the trickiest to work with in their research, and had a large range of issues concerning ownership and primacy. For researchers not well-versed in Tribal SDWIS jurisdiction issues, the Native American owner category can create further confusion. Remember, ownership of Tribal systems is not related to primacy status or Tribal jurisdiction–according to SDWA, any system serving lands under Tribal jurisdiction can be under the primacy of a Tribal government, regardless of who owns it or how they own it.  

    3. EPIC’s preliminary evaluation of discrepancies between data systems show that Native American owner type does not correlate with Tribal lands. We found only 76% of Native American owned systems exist on Tribal land (i.e., Reservations of Trust lands). In other words, systems that have Native American owners exist on and off Tribal lands. 

    1. SDWA data can be filtered by “Tribe Name” on the EPA ECHO Drinking Water Dashboard. Per the Drinking Water Dashboard Help webpage definition: “The association of a facility to a tribe is based on comparing the best available spatial location of the facility to the U.S. Census Bureau’s tribal boundary layer.” In other words, EPA calculates the Tribe Name using spatial analysis based on the facility location, which may not necessarily capture the system service area. It is not clear whether or how Tribe Name relates to the Indian country indicator.

    2. It is also unclear whether the Tribe Name and the Indian county indicators found on the EPA ECHO Drinking Water Dashboard are the same as the similar data elements in the SDWA data downloads. The only information present within the raw data that relate to Tribes include the “area_type_code” and “tribal_code” (which can be referenced to Tribe names, some of which are “NA”), but these fields lack comprehensive definitions such it is difficult to determine whether they contain the same information in the Drinking Water Dashboard. 

The SDWIS Indian country indicator and other Tribal indicators might be missing systems that serve Tribal land and Tribal citizens–sometimes as a result of data entry errors and sometimes as a result of jurisdictional specificities.

  • Based on our own preliminary analysis, only 53% of water system Service Area Boundaries that intersect with Tribal land contain this Indian county flag. That means that 47% of systems intersecting with (and potentially serving) Tribal land are not captured when filtering ECHO reports for the Indian country flag. This analysis is of course preliminary and relies on the Service Area Boundaries data, which has its own issues when it comes to capturing data on Tribal land.

  • In addition to being confusing, this could have implications for the landscape of data that is captured when a data user filters SDWIS data for the Indian country filter. 

    1. Some EPA data systems, like Facility Registry Service (FRS), might classify a CWS as being in Indian country, while another EPA data system, like SDWIS, says that the same system, with the same facility address, is not located in Indian country. Moreover, the Detailed Facility Report would list these differences, but also contains a summary section, where the Indian country indicator says “Yes” if any one of the systems flags the system as being in Indian country, but these CWSs are not included in the search if you are conducting a facility search and filtering for SDWA data and the Indian country flag. Example here.

    2. Thus, there may be systems that are categorized as in Indian country in other EPA ECHO data systems, but are missing the Indian country indicator in SDWIS. Different EPA environmental regulatory data systems may have different definitions of Indian country, or may have different technical processes for assigning the indicator to individual systems, and it is not clear if these missing systems are the result of data errors or regulatory particularities. Regardless, it would impact the world of data that a data user is looking at, and would be important for the user to know. 

    3. For data users, we provide some different EPA ECHO Facility Search filter combinations that could be used to capture systems that are missed by SDWIS’ Indian country indicator in our Explore the Data section.

  • The Indian country flag and other Tribal indicators reflect EPA’s status as a regulator–its Indian country flag only reflects regulatory authority status as it is recognized by EPA.

    1. For example, the Maine Indian Land Claims Settlement Act of 1980 included a provision that subjects federally-recognized Tribes in the state to state laws, and treats reservations like municipalities. The result is that SDWIS data filtered according to any of the elements that would typically be used to identify a Tribal drinking water system (EPA primacy, Indian country flag, Tribe Name) does not capture a single water system serving any of the four federally-recognized Tribes. The water systems serving the Passamaquoddy Tribe’s Pleasant Point reservation, which has been facing severe drinking water quality issues for decades, are not considered “Indian country” in SDWIS, and thus these issues would not surface in any analysis, research, or study of SDWIS data relying on that filter.

Evaluating how Tribal drinking water data limitations are described by EPA. We also found that more meaningful and in-depth discussions of Tribal data limitations and applications would be valuable alongside EPA datasets. 

  • The primary data caveat related to Tribal data is the Tribal lands data quality caveat, which pertains to Indian country and Tribal locations and boundaries–rather than data accuracy within particular datasets–and states that EPA makes no claims regarding their accuracy on EPA’s website. The ECHO Facility Search Criteria Help webpage also contains useful Tribal Lands definitions, some of which note that “the accuracy and completeness of this information varies by data system.” However, these caveats are not particularly useful to researchers or data users who might need to know how Tribal data is inaccurate in a particular dataset. Even with these known data limitations, the EPA maintains the largest, publicly-available dataset on Tribal drinking water. Having more detailed guidance and information on specific data caveats and tips for using these datasets for Tribal drinking water research would be extremely beneficial. 

  • As we discuss below, the documents associated with the Community Water System Service Area Boundaries dataset also lack clarity regarding the accuracy and generation of Tribal data, including on its main webpage, SABs Fact Sheet or the Community Water System Service Area Boundaries State Dataset Summaries.

  • EPA webpages where data users might go to learn more about data problems, especially within specific data sets, are frequently missing any detailed discussion of Tribal data.

    1. EPA ECHO’s Known Data Problems does not include any discussion of Tribal data problems or considerations, for Clean Air Act, Clean Water Act, Resource Conservation and Recovery Act, or SDWA data systems.

Tribal inclusion in the EPA Community Water System Service Area Boundaries dataset. Below we have collated language and information from across documentation associated with SABs to describe how the dataset’s creation and publication may inaccurately represent Tribal drinking water systems.

  • First, this matters because the dataset scope on the main landing page and in the Fact Sheet states that “this dataset extends to all 50 states and Washington, DC as well as tribal systems.” The limitations section of the webpage and fact sheet both also include statements that systems may be missing from the dataset if “your water comes from a community water system that is not mapped due to model input limitations that did not produce reliable/accurate boundaries. For example, many tribal and territorial community water systems are not mapped for this reason.” In our view, the introductory statement could be understood by data users to imply that the dataset includes data for Tribal lands at an equal data quality level as state data, and is inconsistent with the limitations statement. As we will describe, this does not seem to be the case.  

  • Per the associated Fact Sheet, the service area boundaries dataset was developed using a combination of data sources–40% of boundaries were reported directly by states whose datasets were determined by EPA to be of high quality, 10% of boundaries were reported to the EPA directly by water systems, and 50% of boundaries were modeled.

    1. First, it does not appear that Tribes participated in the creation or validation of this dataset. It is unlikely that the state-reported boundaries included water systems on Tribal lands, as that data would be maintained by Tribes, who are not required to share their data with states. 

    2. EPA-modeled data was developed using a “a variety of inputs, such as, building footprints and service connections,” relying primarily on historic Census data, and then validated using boundaries data reported by several states judged to have very robust boundaries datasets. Census data is historically underreported for American Indians and Alaska Natives and on Tribal lands, and the state data used to validate the models probably excluded Tribal data (see note above).

  • The EPA Water System Service Area Technical Documentation notes that there are several types of water systems missing from the dataset because they could not be modeled, and that “a good portion of the systems that could not be modeled were not modeled.” 

    1. In addition to the fact that the dataset scope overall excludes private wells, and non-community water systems, systems that could not be modeled by EPA included small systems with fewer than 100 connections as well as systems serving mobile home parks and subdivisions.

    2. Thus, communities with more of these system types might disproportionately be missing data, or might have incorrectly mapped data, if any of these systems were modeled. Tribes tend to disproportionately be served by small systems, wells, and a recent study indicates that Tribal communities may have more mobile home parks–four times the number of home purchase loans on Tribal lands versus off Tribal lands are used to purchase mobile homes.

  • Finally, the Service Area Boundaries dataset map does not map Tribal lands, and users cannot filter the map to show CWSs that have the Indian country or Tribe Name indicator. To review SABs for Tribal lands, a data user would need to download the SABs geospatial dataset and analyze it in combination with Tribal boundary geospatial data to identify systems with SABs on Tribal lands. However, this may not be too big of an issue given the data limitations identified above.

Explore the data yourself

The EPA ECHO dataset includes several data elements that a user can filter in data downloads or in EPA ECHO to understand Tribal drinking water access