Groundwater, Aquifers, Wells, and Springs

MODFLOW is the USGS's modular hydrologic model. MODFLOW is considered an international standard for simulating and predicting groundwater conditions and groundwater/surface-water interactions. MODFLOW 6 is presently the core MODFLOW version distributed by the USGS. The previous core version, MODFLOW-2005, is actively maintained and supported as well.

Did you know that earthquakes can cause changes in groundwater levels? Very large earthquakes can even cause water-level fluctuations in some wells thousands of miles away, depending on the local geological conditions around the well.

Karst terrain is created from the dissolution of soluble rocks, principally limestone and dolomite. Karst areas are characterized by distinctive landforms (like springs, caves, sinkholes) and a unique hydrogeology that results in aquifers that are highly productive but extremely vulnerable to contamination.

The U.S. Geological Survey is integrating its water science programs to better address the Nation’s greatest water resource challenges. At the heart of this effort are plans to intensively study at least 10 Integrated Water Science (IWS) basins — medium-sized watersheds (10,000-20,000 square miles) and underlying aquifers — over the next decade. The IWS basins will represent a wide range of...

Substantial advances in water science, together with emerging breakthroughs in technical and computational capabilities, have led the USGS to develop a Next Generation Water Observing System (NGWOS). The USGS NGWOS will provide real-time data on water quantity and quality in more affordable and rapid ways than previously possible, and in more locations.

The USGS Integrated Water Availability Assessments (IWAAs) are a multi-extent, stakeholder driven, near real-time census and prediction of water availability for both human and ecological uses at regional and national extents.

Integrated Water Availability Assessments examine water supply, use, and availability. Snow from the Upper Colorado River Basin contributes 92% of the natural streamflow to the entire Colorado River Basin. The UCOL IWAAs will improve our understanding of the water budget, status and trends in water quality and ecological conditions, and ecosystem response to changes in climate and human water use.

Integrated Water Availability Assessments examine water supply, use, and availability. In the Delaware River Basin, which serves over 13 million people, water availability can be affected by drought, river temperature, salinity, and more. The Delaware River Basin IWAAs will investigate these and other water quantity, quality, and use issues to assess available water and how it changes over time.

The Next Generation Water Observing System provides high-fidelity, real-time data on water quantity, quality, and use to support modern water prediction and decision-support systems that are necessary for informing water operations on a daily basis and decision-making during water emergencies. The Illinois River Basin provides an opportunity to implement the NGWOS in a system challenged by an...

The Next Generation Water Observing System (NGWOS) provides high-fidelity, real-time data on water quantity, quality, and use to support modern prediction and decision-support systems that are necessary for informing water operations on a daily basis and decision-making during water emergencies. The headwaters of the Colorado and Gunnison River Basins provide an opportunity to implement NGWOS in a...

This website compiles USGS resources and data related to principal aquifers including Aquifer Basics, principal aquifers maps and GIS data, and the National Aquifer Code Reference List.

This list of national principal aquifer codes and names are fixed values assigned by the National Water Information System (NWIS). Aquifers are identified by a geohydrologic unit code - a three-digit number related to the age of the formation, followed by a 4 or 5 character abbreviation for the geologic unit or aquifer name.