The United States sits above hundreds of distinct aquifer systems that supply drinking water to roughly 150 million Americans and irrigate millions of acres of farmland. This interactive US aquifer map shows every principal aquifer across the contiguous 48 states, Hawaii, Puerto Rico, and the U.S. Virgin Islands, coloured by the type of rock or sediment that holds the water. Filter by rock type to isolate specific aquifer categories, then click any polygon to see the aquifer name and approximate area.
Explore US Aquifer Locations
How to Use This Map
Filter by Rock Type
Use the checkboxes to show or hide aquifers by the rock or sediment type that makes up the aquifer. Each type is assigned a distinct colour — sandy amber for unconsolidated sand and gravel, pale gold for semiconsolidated sand, terracotta for sandstone, brown-orange for sandstone and carbonate, teal for carbonate rock, and slate purple for igneous and metamorphic rock.
Read the Popup
Click any coloured polygon to see the aquifer’s formal name and its approximate area. The coloured badge shows the rock type classification used by the USGS.
Find Aquifers Near You
Click Near Me to jump to your current location and see which aquifer system — if any — lies beneath you. Much of the central and western US sits above significant aquifer systems that are not visible at street level but are critical for local water supply.
What Is an Aquifer?
An aquifer is an underground layer of permeable rock, sediment, or soil that holds and transmits groundwater. Water enters an aquifer through a recharge zone — typically an area where rainfall or snowmelt percolates downward through permeable surface material — and can be extracted via wells for drinking water, irrigation, and industrial use.
Aquifers vary enormously in depth, thickness, and water quality. Some are shallow and quickly recharged by local precipitation. Others, called fossil aquifers, contain water deposited thousands of years ago and recharge so slowly that pumping effectively depletes them.
Six Aquifer Rock Types
The USGS classifies principal aquifers by the type of rock or sediment that stores the groundwater:
- Unconsolidated sand and gravel — The most widespread and productive aquifer material in the US. Loose sand and gravel particles have large pore spaces that hold substantial volumes of water and allow it to flow freely to wells. Most major alluvial aquifers fall into this category.
- Semiconsolidated sand — Partially cemented sand layers, typically found in coastal plain sediments. Productive but less permeable than fully unconsolidated material.
- Sandstone — Cemented sand grains with pore spaces between them. Many deep bedrock aquifers in the midwest and east are sandstone formations.
- Sandstone and carbonate-rock — Mixed formations containing both sandstone and carbonate (limestone or dolomite) layers. Common in the central US.
- Carbonate-rock — Limestone and dolomite aquifers. Water dissolves the rock over time, creating caves and solution channels (karst) that can transmit enormous volumes of water extremely rapidly — making them both highly productive and vulnerable to contamination.
- Igneous and metamorphic rock — Hard crystalline rock with little primary porosity. Groundwater is stored and transmitted through fractures. Yields are typically lower than sedimentary aquifers, but these systems are important in areas like the Appalachians and parts of New England where no other aquifer exists.
Major US Aquifer Systems
While there are 71 named principal aquifer units in this dataset, a handful account for the majority of US groundwater use:
- High Plains Aquifer (Ogallala) — The largest aquifer in North America, underlying about 174,000 square miles across eight states from South Dakota to Texas. It supplies roughly 30% of all groundwater used for irrigation in the US, but in many areas water levels are declining faster than natural recharge can replace them.
- Central Valley Aquifer System — Underlies California’s San Joaquin and Sacramento valleys. Critical for agriculture in one of the world’s most productive farming regions, but decades of over-pumping have caused significant land subsidence.
- Floridan Aquifer System — One of the most productive aquifer systems in the world, supplying water to Florida, Georgia, South Carolina, and Alabama. A carbonate-rock system with high natural recharge from Florida’s abundant rainfall.
- Mississippi River Valley Alluvial Aquifer — An unconsolidated sand and gravel aquifer along the lower Mississippi River, heavily used for agriculture across Arkansas, Mississippi, Louisiana, and neighbouring states.
- Edwards-Trinity Aquifer System — A carbonate-rock aquifer underlying central Texas. Feeds numerous springs including Barton Springs in Austin and is the primary water source for San Antonio.
- Columbia Plateau Basaltic-rock Aquifers — Volcanic basalt aquifers underlying the Columbia Plateau in Washington, Oregon, and Idaho, fed by recharge from the Cascade Range.
Aquifers and Surface Water
Aquifers and surface water are closely connected. Many rivers and streams are sustained during dry periods entirely by groundwater discharge — when the water table drops below a streambed, the stream can lose water to the aquifer instead of gaining it, a transition visible in declining baseflows across much of the American West. You can monitor current streamflow levels with our live stream gauge map, and trace the drainage networks that feed these systems with our interactive US watershed map.
Federal lands play a significant role in aquifer recharge. National forests in particular act as water towers, with snowpack and forest soils filtering precipitation into underlying aquifers. Our US federal lands map shows the full extent of federally managed land and how it overlaps with major aquifer recharge zones.
Data Source
This map uses the USA Aquifers feature layer from the ArcGIS Living Atlas of the World, published by Esri and sourced from the USGS Ground Water Atlas of the United States. The dataset covers the principal aquifers of the 48 contiguous states, Hawaii, Puerto Rico, and the U.S. Virgin Islands. Area figures are approximate, derived from feature geometry corrected for Web Mercator projection distortion.
Frequently Asked Questions
How do I find out which aquifer supplies my well?
Zoom to your location using the Near Me button to see which aquifer polygon covers your area. For well-specific information including depth, water quality, and historical water levels, the USGS National Water Information System (NWIS) maintains records for millions of monitored wells across the US.
Why are some areas not covered by any aquifer polygon?
The dataset shows principal aquifers — regionally significant systems used for water supply. Areas not covered may overlie minor local aquifers, have groundwater in fractured rock too variable to map at this scale, or simply lack significant groundwater resources. Absence from this map does not mean no groundwater exists.
Is the High Plains Aquifer really running out?
In many areas, yes. Pumping for irrigation has lowered water levels by more than 100 feet in parts of Kansas, Texas, and Oklahoma since the 1950s. Some areas have seen levels recover during wet years, but the long-term trend in the southern High Plains is depletion. The northern High Plains, particularly in Nebraska, is in better condition due to higher natural recharge rates.
What makes carbonate aquifers different from other types?
Carbonate (limestone and dolomite) aquifers develop solution cavities and conduit networks over time as slightly acidic groundwater dissolves the rock. This karst plumbing can transmit water very rapidly — sometimes at rates more typical of surface streams than porous media — which makes them highly productive but also highly susceptible to contamination. Pollutants introduced at the surface can travel kilometres through karst systems in hours.
How current is this aquifer data?
The dataset is based on the USGS Ground Water Atlas of the United States, originally published in the 1990s and early 2000s. Aquifer boundaries at this national scale change slowly, so the data remains accurate for general reference. For site-specific work or regulatory purposes, consult the relevant state geological survey or USGS water science centre.
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