| #D001 | | Aquifer | An aquifer is an underground body of rock that contains and can transmit groundwater. | high |
| #D002 | | SWC | Source Water Collaboratives | high |
| #D003 | | SSA | Sole Source Aquifers | high |
| #D004 | | NLCD | National Land Cover Database | high |
| #D005 | | MRLC | Multi-Resolution Land Characteristics | high |
| #D006 | | PAD-US | Protected Areas Database of the United States | high |
| #D007 | | NPDES | National Pollutant Discharge Elimination System | high |
| #D008 | | RAD | Reach Address Database | high |
| #D009 | | WATERS | Watershed Assessment, Tracking & Environmental Results System | high |
| #D010 | | FRS | Facility Registry Service | high |
| #D011 | | FMCSA | Federal Motor Carrier Safety Administration | high |
| #D012 | | NTAD | National Transportation Atlas Database | high |
| #D013 | | GRTS | Grant Reporting and Tracking system | high |
| #D014 | | TMDL | Total Maximum Daily Load | high |
| #D015 | | WBD | Watershed Boundaries Dataset | high |
| #D016 | | NHD | National Hydrography Dataset | high |
| #D017 | | aquifer | An aquifer is an underground body of rock that contains and can transmit groundwater. | high |
| #D018 | | USGS | United States Geological Survey | high |
| #D019 | | HU2 | Regions | high |
| #D020 | | HU4 | Subregions | high |
| #D021 | | HU6 | Basins | high |
| #D022 | | HU8 | Subbasins | high |
| #D023 | | HU10 | Watersheds | high |
| #D024 | | HU12 | Subwatersheds | high |
| #D025 | | DWMAPS | Drinking Water Mapping Application to Protect Source Waters | high |
| #D026 | | source water collaboratives | local, state, and watershed-based partnerships working to protect sources of drinking water | high |
| #D027 | | 305(b) Assessed Waters | 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. | high |
| #D028 | | 303(d) Listed Impaired Waters | 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. | high |
| #D029 | | Aquifer Exemptions | 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. | high |
| #D030 | | National Land Cover Database (NLCD) | The National Land Cover Database (NLCD) serves as the definitive Landsat-based, 30-meter resolution, land cover database for the nation. | high |
| #D031 | | Watershed Boundaries Dataset (WBD) | The WBD defines the areal extent or perimeter of surface water drainage areas formed by the terrain and other landscape characteristics. | high |
| #D032 | | National Hydrography Dataset (NHD) | 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. | high |
| #D033 | | 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. | high |
| #D034 | | SDWA | Safe Drinking Water Act | high |
| #D035 | | Safe Drinking Water Act | The Safe Drinking Water Act (SDWA) was originally passed by Congress in 1974 to protect public health by regulating the nation’s public drinking water supply. | high |
| #D036 | | NDWAC | National Drinking Water Advisory Council | high |
| #D037 | | MS4 | municipal separate storm sewer systems | high |
| #D038 | | SWMP | stormwater management program | high |
| #D039 | | BMPs | best management practices | high |
| #D040 | | SWPPP | Stormwater Pollution Prevention Plan | high |
| #D041 | | illicit discharge | any discharge to an MS4 that is not composed entirely of stormwater | high |
| #D042 | | CMBM | Chemical Mass Balance Model | high |
| #D043 | | LID | low impact development | high |
| #D044 | | NPS | Nonpoint Source | high |
| #D045 | | TMDL | Total Maximum Daily Load | high |
| #D046 | | NPDES | National Pollutant Discharge Elimination System | high |