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Source Water Protection (SWP)

Drinking Water Mapping Application to Protect Source Waters (DWMAPS) Data Layers


DWMAPS Data Layers

Use links on this table to access data layers used in DWMAPS.

Data Layer and URLs Description

Source Water Collaboratives (SWC)

This map service displays local, state, and watershed-based partnerships working to protect sources of drinking water (a.k.a. source water collaboratives). Source water collaborative organizations provided organization summaries and geographic locations. Watershed collaboratives (Watershed_Regional_Collaboratives) polygons were generated with watershed delineations obtained from the Unites States Geological Survey National Hydrography Dataset, Watershed Boundary Dataset. Data are available at all scales for public use and access.

Sole Source Aquifers (SSA)

These data include a national Sole Source Aquifer (SSA) layer, including all available SSA coverages.

Aquifer Exemptions

This map service provides locations of Aquifer Exemptions. An aquifer is an underground body of rock that contains and can transmit groundwater. The EPA exempts aquifers if the aquifer does not currently serve as a source of drinking water and will not serve as a source of drinking water in the future, based on certain criteria. Aquifer Exemption locations and/or boundaries are displayed as a two dimensional boundary centroid, county-level polygon, or precise boundary polygon. DWMAPS provides viewing access to county and precise area aquifer exemption layers. For more information, visit

Land Cover

The National Land Cover Database (NLCD) serves as the definitive Landsat-based, 30-meter resolution, land cover database for the nation. NLCD provides spatial reference and descriptive data for characteristics of the land surface such as thematic class (for example, urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover. NLCD supports a wide variety of Federal, State, local, and nongovernmental applications that seek to assess ecosystem status and health, understand the spatial patterns of biodiversity, predict effects of climate change, and develop land management policy. NLCD products are created by the Multi-Resolution Land Characteristics (MRLC) Consortium, a partnership of Federal agencies led by the U.S. Geological Survey. The Land Cover layer includes grid layers for the NLCD 1992, NLCD 2001, NLCD 2006, and NLCD 2011. For more information, visit

Protected Areas

The United States Geological Survey (USGS) Protected Areas Database of the United States (PAD-US) is the nation’s inventory of protected areas, including public open space and voluntarily provided, private protected areas. The PAD-US database strives to be a complete “best available” inventory of areas dedicated to the preservation of biological diversity, and other natural, recreational or cultural uses, managed for these purposes through legal or other effective means. For more information, visit

Facilities Permitted to Discharge to Water

This map service contains GIS data for National Pollutant Discharge Elimination System (NPDES) facilities that discharge to water indexed to the National Hydrography Dataset, NHDPlus Version 2.1. The information supporting this service resides in the EPA Reach Address Database (RAD) which is part of the Watershed Assessment, Tracking & Environmental Results System (WATERS). Reach indexed NPDES locations comprise two basic types: facilities and pipes. For a given NPDES permit, the program may have locational information on the facility alone or specific pipe outfalls.

Facility Registry Service (FRS)

The FRS map service provides location and attribute information on facilities, sites or places subject to environmental regulations or environmental interest. This service provides users with access to FRS information through various interfaces, including WMS, REST, WFS, SOAP, and more. For more information about the Facility Registry Service, visit

Roads, Hazardous Materials Routes

This dataset, utilizing data from the Federal Motor Carrier Safety Administration (FMCSA) contains state-assigned hazardous material routes developed using data from the 2012 National Transportation Atlas Database (NTAD). The dataset is maintained by the U.S. Department of Transportation. For more information, visit


The US Rail Network for both freight and passenger lines. For more information, visit

305(b) Assessed Waters

GIS data from the EPA Office of Water 305(b) Assessed Waters Program. The 305(b) program provides assessed water data and assessed water features for river segments, lakes, and estuaries designated under Section 305(b) of the Clean Water Act. For the web service, 305(b) waterbodies are coded onto the National Hydrography Dataset, NHDPlus v2.1, features creating area, point and linear events representing assessed and non-assessed waters.

303 (d) Listed Impaired Waters

GIS data from the EPA Office of Water 303(d) Program. The 303(d) Listed Impaired Waters program system provides impaired water data and impaired water features reflecting river segments, lakes, and estuaries designated under Section 303(d) of the Clean Water Act. For the web service, 303(d) waterbodies are coded onto the National Hydrography Dataset, NHDPlus v2.1, flowline and waterbody features to create line, area, and point events.

CWA Section 319 Nonpoint Source Grant Projects

GIS data from the EPA Office of Water Grant Reporting and Tracking system (GRTS), which includes locational data for Clean Water Act Section 319 nonpoint source projects. For the web service, GRTS locations are coded onto the National Hydrography Dataset, NHDPlus v2.1, flowline and waterbody features to create line, area, and point events.

Total Maximum Daily Load (TMDL)

GIS data about Total Maximum Daily Loads (TMDL) from the EPA Office of Water. For the web service, TMDLs on 303(d) waterbodies are coded onto the National Hydrography Dataset, NHDPlus v2.1, flowline and waterbody features to create line, area, and point events.

Tribal Areas

This layer represents locations of American Indian Tribal lands in the lower 48 states. The areas include all lands associated with Federally recognized tribal entities--Federally recognized Reservations, Off-Reservation Trust Lands, and Census Oklahoma Tribal Statistical Areas.

Watershed Boundaries (HUC12)

This layer contains GIS data from the United States Geological Survey (USGS) Watershed Boundaries Dataset (WBD). The WBD is made up of polygons nested into seven levels of data to include Regions (HU2), Subregions (HU4), Basins (HU6), Subbasins (HU8), Watersheds (HU10), Subwatersheds (HU12), and HU14. The WBD defines the areal extent or perimeter of surface water drainage areas formed by the terrain and other landscape characteristics.

National Hydrography Dataset

The National Hydrography Dataset (NHD) represents the water drainage network of the United States with features such as rivers, streams, canals, lakes, ponds, coastline, dams, and streamgages. The NHD is the surface water component on the US Topo map product produced by the USGS. The web service, hosted by EPA Office of Water, contains point, line, and polygon layers depicting Medium Resolution National Hydrography Dataset features from the NHDPlus version 2.1.


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